From 3f237a79ddeea34dda67e9eedece3a22918df75e Mon Sep 17 00:00:00 2001
From: Rusty Russell
Date: Fri, 12 Jun 2009 21:15:30 +0930
Subject: cpumask: use new operators in kernel/trace

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <200906122115.30787.rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/kmemtrace.c   | 2 +-
 kernel/trace/ring_buffer.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/kmemtrace.c b/kernel/trace/kmemtrace.c
index 86cdf671d7e2..1edaa9516e81 100644
--- a/kernel/trace/kmemtrace.c
+++ b/kernel/trace/kmemtrace.c
@@ -186,7 +186,7 @@ static int kmem_trace_init(struct trace_array *tr)
 	int cpu;
 	kmemtrace_array = tr;
 
-	for_each_cpu_mask(cpu, cpu_possible_map)
+	for_each_cpu(cpu, cpu_possible_mask)
 		tracing_reset(tr, cpu);
 
 	kmemtrace_start_probes();
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2e642b2b7253..9c31c9f6b93f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3105,7 +3105,7 @@ static int rb_cpu_notify(struct notifier_block *self,
 	switch (action) {
 	case CPU_UP_PREPARE:
 	case CPU_UP_PREPARE_FROZEN:
-		if (cpu_isset(cpu, *buffer->cpumask))
+		if (cpumask_test_cpu(cpu, buffer->cpumask))
 			return NOTIFY_OK;
 
 		buffer->buffers[cpu] =
@@ -3116,7 +3116,7 @@ static int rb_cpu_notify(struct notifier_block *self,
 			return NOTIFY_OK;
 		}
 		smp_wmb();
-		cpu_set(cpu, *buffer->cpumask);
+		cpumask_set_cpu(cpu, buffer->cpumask);
 		break;
 	case CPU_DOWN_PREPARE:
 	case CPU_DOWN_PREPARE_FROZEN:
-- 
cgit v1.2.3


From 215368e8e59023d6a0abdda896923018d74fdf7f Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Mon, 15 Jun 2009 10:56:42 +0800
Subject: tracing: fix a typo in tracing_cpumask_write()

It's tracing_cpumask_new that should be kfree()ed.

This causes tracing_cpumask to be freed due to the typo:

 # echo z > tracing_cpumask
 bash: echo: write error: Invalid argument

And subsequent reads/writes to tracing_cpuamsk will access this
already-freed tracing_cpumask, thus may lead to crash.

[ Impact: fix leak and crash when writing invalid val to tracing_cpumask ]

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B86A.7070608@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8acd9b81a5d7..7355a38e18be 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2191,11 +2191,12 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
 	if (!alloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
 		return -ENOMEM;
 
-	mutex_lock(&tracing_cpumask_update_lock);
 	err = cpumask_parse_user(ubuf, count, tracing_cpumask_new);
 	if (err)
 		goto err_unlock;
 
+	mutex_lock(&tracing_cpumask_update_lock);
+
 	local_irq_disable();
 	__raw_spin_lock(&ftrace_max_lock);
 	for_each_tracing_cpu(cpu) {
@@ -2223,8 +2224,7 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
 	return count;
 
 err_unlock:
-	mutex_unlock(&tracing_cpumask_update_lock);
-	free_cpumask_var(tracing_cpumask);
+	free_cpumask_var(tracing_cpumask_new);
 
 	return err;
 }
-- 
cgit v1.2.3


From e4f2d10f479d18198ebafcb5e124cc3dd8b8817a Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Mon, 15 Jun 2009 10:57:28 +0800
Subject: tracing: replace a GFP_ATOMIC with GFP_KERNEL allocation

Atomic allocation is not needed here.

[ Impact: clean up of memory alloction type ]

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B898.2050607@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7355a38e18be..0f57f1b443b6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3627,7 +3627,7 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
 	struct trace_seq *s;
 	unsigned long cnt;
 
-	s = kmalloc(sizeof(*s), GFP_ATOMIC);
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
 	if (!s)
 		return ENOMEM;
 
-- 
cgit v1.2.3


From 5e4904cb633177046bee5d26946a7ac918e642fc Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Mon, 15 Jun 2009 10:58:39 +0800
Subject: tracing/filters: operand can be negative

This should be a bug:

 # cat format
 name: foo_bar
 ID: 71
 format:
	 ...
         field:int bar;  offset:24;      size:4;
 # echo 'bar < 0' > filter
 # echo 'bar < -1' > filter
 bash: echo: write error: Invalid argument

[ Impact: fix to allow negative operand in filer expr ]

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B8DF.60400@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index db6e54bdb596..1d8192304842 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -546,6 +546,7 @@ static int filter_add_pred(struct filter_parse_state *ps,
 	filter_pred_fn_t fn;
 	unsigned long long val;
 	int string_type;
+	int ret;
 
 	pred->fn = filter_pred_none;
 
@@ -581,7 +582,11 @@ static int filter_add_pred(struct filter_parse_state *ps,
 			pred->not = 1;
 		return filter_add_pred_fn(ps, call, pred, fn);
 	} else {
-		if (strict_strtoull(pred->str_val, 0, &val)) {
+		if (field->is_signed)
+			ret = strict_strtoll(pred->str_val, 0, &val);
+		else
+			ret = strict_strtoull(pred->str_val, 0, &val);
+		if (ret) {
 			parse_error(ps, FILT_ERR_ILLEGAL_INTVAL, 0);
 			return -EINVAL;
 		}
-- 
cgit v1.2.3


From 0ac2058f686a19fe8ab25c4f3104fc1580dce7cf Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Mon, 15 Jun 2009 10:59:17 +0800
Subject: tracing/filters: strloc should be unsigned short

I forgot to update filter code accordingly in
"tracing/events: change the type of __str_loc_item to unsigned short"
(commt b0aae68cc5508f3c2fbf728988c954db4c8b8a53)

It can cause system crash:

 # echo 1 > tracing/events/irq/irq_handler_entry/enable
 # echo 'name == eth0' > tracing/events/irq/irq_handler_entry/filter

[ Impact: fix crash while filtering on __string() field ]

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B905.3090500@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 1d8192304842..b24ab0e6ea74 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -178,7 +178,7 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
 static int filter_pred_strloc(struct filter_pred *pred, void *event,
 			      int val1, int val2)
 {
-	int str_loc = *(int *)(event + pred->offset);
+	unsigned short str_loc = *(unsigned short *)(event + pred->offset);
 	char *addr = (char *)(event + str_loc);
 	int cmp, match;
 
-- 
cgit v1.2.3


From c7b0930857e2278f2e7714db6294e94c57f623b0 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Thu, 11 Jun 2009 11:12:00 -0400
Subject: ring-buffer: prevent adding write in discarded area

This a very tight race where an interrupt could come in and not
have enough data to put into the end of a buffer page, and that
it would fail to write and need to go to the next page.

But if this happened when another writer was about to reserver
their data, and that writer has smaller data to reserve, then
it could succeed even though the interrupt moved the tail page.

To pervent that, if we fail to store data, and by subtracting the
amount we reserved we still have room for smaller data, we need
to fill that space with "discarded" data.

[ Impact: prevent race were buffer data may be lost ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 68 ++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 56 insertions(+), 12 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9c31c9f6b93f..dbc0f93396aa 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -205,6 +205,7 @@ EXPORT_SYMBOL_GPL(tracing_is_on);
 #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
 #define RB_ALIGNMENT		4U
 #define RB_MAX_SMALL_DATA	(RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+#define RB_EVNT_MIN_SIZE	8U	/* two 32bit words */
 
 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
@@ -1170,6 +1171,59 @@ static unsigned rb_calculate_event_length(unsigned length)
 	return length;
 }
 
+static inline void
+rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
+	      struct buffer_page *tail_page,
+	      unsigned long tail, unsigned long length)
+{
+	struct ring_buffer_event *event;
+
+	/*
+	 * Only the event that crossed the page boundary
+	 * must fill the old tail_page with padding.
+	 */
+	if (tail >= BUF_PAGE_SIZE) {
+		local_sub(length, &tail_page->write);
+		return;
+	}
+
+	event = __rb_page_index(tail_page, tail);
+
+	/*
+	 * If this event is bigger than the minimum size, then
+	 * we need to be careful that we don't subtract the
+	 * write counter enough to allow another writer to slip
+	 * in on this page.
+	 * We put in a discarded commit instead, to make sure
+	 * that this space is not used again.
+	 *
+	 * If we are less than the minimum size, we don't need to
+	 * worry about it.
+	 */
+	if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
+		/* No room for any events */
+
+		/* Mark the rest of the page with padding */
+		rb_event_set_padding(event);
+
+		/* Set the write back to the previous setting */
+		local_sub(length, &tail_page->write);
+		return;
+	}
+
+	/* Put in a discarded event */
+	event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
+	event->type_len = RINGBUF_TYPE_PADDING;
+	/* time delta must be non zero */
+	event->time_delta = 1;
+	/* Account for this as an entry */
+	local_inc(&tail_page->entries);
+	local_inc(&cpu_buffer->entries);
+
+	/* Set write to end of buffer */
+	length = (tail + length) - BUF_PAGE_SIZE;
+	local_sub(length, &tail_page->write);
+}
 
 static struct ring_buffer_event *
 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
@@ -1264,17 +1318,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 		cpu_buffer->tail_page->page->time_stamp = *ts;
 	}
 
-	/*
-	 * The actual tail page has moved forward.
-	 */
-	if (tail < BUF_PAGE_SIZE) {
-		/* Mark the rest of the page with padding */
-		event = __rb_page_index(tail_page, tail);
-		rb_event_set_padding(event);
-	}
-
-	/* Set the write back to the previous setting */
-	local_sub(length, &tail_page->write);
+	rb_reset_tail(cpu_buffer, tail_page, tail, length);
 
 	/*
 	 * If this was a commit entry that failed,
@@ -1293,7 +1337,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 
  out_reset:
 	/* reset write */
-	local_sub(length, &tail_page->write);
+	rb_reset_tail(cpu_buffer, tail_page, tail, length);
 
 	if (likely(lock_taken))
 		__raw_spin_unlock(&cpu_buffer->lock);
-- 
cgit v1.2.3


From 9086c7b90abbf4ec29543e8f2424e3ecd14e955d Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Tue, 16 Jun 2009 11:46:09 -0400
Subject: ring-buffer: have benchmark test handle discarded events

With the addition of commit:

  c7b0930857e2278f2e7714db6294e94c57f623b0
  ring-buffer: prevent adding write in discarded area

The ring buffer may now add discarded events when a write passes
the end of a buffer page. Before, a discarded event was only added
when the tracer deliberately created one. The ring buffer benchmark
test does not handle discarded events when it reads the buffer and
fails when it encounters one.

Also fix the increment for large data entries (luckily, the test did
not add any yet).

[ Impact: fix false failure of ring buffer self test ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer_benchmark.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 8d68e149a8b3..cf6b0f50134e 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -102,8 +102,10 @@ static enum event_status read_page(int cpu)
 			event = (void *)&rpage->data[i];
 			switch (event->type_len) {
 			case RINGBUF_TYPE_PADDING:
-				/* We don't expect any padding */
-				KILL_TEST();
+				/* failed writes may be discarded events */
+				if (!event->time_delta)
+					KILL_TEST();
+				inc = event->array[0] + 4;
 				break;
 			case RINGBUF_TYPE_TIME_EXTEND:
 				inc = 8;
@@ -119,7 +121,7 @@ static enum event_status read_page(int cpu)
 					KILL_TEST();
 					break;
 				}
-				inc = event->array[0];
+				inc = event->array[0] + 4;
 				break;
 			default:
 				entry = ring_buffer_event_data(event);
-- 
cgit v1.2.3


From 263294f3e1e883b9dcbf0c09a54b644918f7729d Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Tue, 16 Jun 2009 11:50:18 -0400
Subject: ring-buffer: remove unused variable

Fix the compiler error:

kernel/trace/ring_buffer.c: In function 'rb_move_tail':
kernel/trace/ring_buffer.c:1236: warning: unused variable 'event'

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 1 -
 1 file changed, 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index dbc0f93396aa..e857e9443987 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1233,7 +1233,6 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 {
 	struct buffer_page *next_page, *head_page, *reader_page;
 	struct ring_buffer *buffer = cpu_buffer->buffer;
-	struct ring_buffer_event *event;
 	bool lock_taken = false;
 	unsigned long flags;
 
-- 
cgit v1.2.3


From fa7439531dee58277748c819785a44d3203c4b51 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Tue, 16 Jun 2009 12:37:57 -0400
Subject: ring-buffer: use commit counters for commit pointer accounting

The ring buffer is made up of three sets of pointers.

The head page pointer, which points to the next page for the reader to
get.

The commit pointer and commit index, which points to the page and index
of the last committed write respectively.

The tail pointer and tail index, which points to the page and the index
of the last reserved data respectively (non committed).

The commit pointer is only moved forward by the outer most writer.
If a nested writer comes in, it will not move the pointer forward.

The current implementation has a flaw. It assumes that the outer most
writer successfully reserved data. There's a small race window where
the outer most writer could find the tail pointer, but a nested
writer could come in (via interrupt) and move the tail forward, and
even the commit forward.

The outer writer would not realized the commit moved forward and the
accounting will break.

This patch changes the design to use counters in the per cpu buffers
to keep track of commits. The counters are incremented at the start
of the commit, and decremented at the end. If the end commit counter
is 1, then it moves the commit pointers. A loop is made to check for
races between checking and moving the commit pointers. Only the outer
commit should move the pointers anyway.

The test of knowing if a reserve is equal to the last commit update
is still needed to know for time keeping. The time code is much less
racey than the commit updates.

This change not only solves the mentioned race, but also makes the
code simpler.

[ Impact: fix commit race and simplify code ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 154 ++++++++++++++++++++++-----------------------
 1 file changed, 75 insertions(+), 79 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e857e9443987..ed3559944fcf 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -415,6 +415,8 @@ struct ring_buffer_per_cpu {
 	unsigned long			overrun;
 	unsigned long			read;
 	local_t				entries;
+	local_t				committing;
+	local_t				commits;
 	u64				write_stamp;
 	u64				read_stamp;
 	atomic_t			record_disabled;
@@ -1015,8 +1017,8 @@ rb_event_index(struct ring_buffer_event *event)
 }
 
 static inline int
-rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
-	     struct ring_buffer_event *event)
+rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
+		   struct ring_buffer_event *event)
 {
 	unsigned long addr = (unsigned long)event;
 	unsigned long index;
@@ -1028,31 +1030,6 @@ rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
 		rb_commit_index(cpu_buffer) == index;
 }
 
-static void
-rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
-		    struct ring_buffer_event *event)
-{
-	unsigned long addr = (unsigned long)event;
-	unsigned long index;
-
-	index = rb_event_index(event);
-	addr &= PAGE_MASK;
-
-	while (cpu_buffer->commit_page->page != (void *)addr) {
-		if (RB_WARN_ON(cpu_buffer,
-			  cpu_buffer->commit_page == cpu_buffer->tail_page))
-			return;
-		cpu_buffer->commit_page->page->commit =
-			cpu_buffer->commit_page->write;
-		rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-		cpu_buffer->write_stamp =
-			cpu_buffer->commit_page->page->time_stamp;
-	}
-
-	/* Now set the commit to the event's index */
-	local_set(&cpu_buffer->commit_page->page->commit, index);
-}
-
 static void
 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 {
@@ -1319,15 +1296,6 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 
 	rb_reset_tail(cpu_buffer, tail_page, tail, length);
 
-	/*
-	 * If this was a commit entry that failed,
-	 * increment that too
-	 */
-	if (tail_page == cpu_buffer->commit_page &&
-	    tail == rb_commit_index(cpu_buffer)) {
-		rb_set_commit_to_write(cpu_buffer);
-	}
-
 	__raw_spin_unlock(&cpu_buffer->lock);
 	local_irq_restore(flags);
 
@@ -1377,11 +1345,11 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 		local_inc(&tail_page->entries);
 
 	/*
-	 * If this is a commit and the tail is zero, then update
-	 * this page's time stamp.
+	 * If this is the first commit on the page, then update
+	 * its timestamp.
 	 */
-	if (!tail && rb_is_commit(cpu_buffer, event))
-		cpu_buffer->commit_page->page->time_stamp = *ts;
+	if (!tail)
+		tail_page->page->time_stamp = *ts;
 
 	return event;
 }
@@ -1450,16 +1418,16 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
 		return -EAGAIN;
 
 	/* Only a commited time event can update the write stamp */
-	if (rb_is_commit(cpu_buffer, event)) {
+	if (rb_event_is_commit(cpu_buffer, event)) {
 		/*
-		 * If this is the first on the page, then we need to
-		 * update the page itself, and just put in a zero.
+		 * If this is the first on the page, then it was
+		 * updated with the page itself. Try to discard it
+		 * and if we can't just make it zero.
 		 */
 		if (rb_event_index(event)) {
 			event->time_delta = *delta & TS_MASK;
 			event->array[0] = *delta >> TS_SHIFT;
 		} else {
-			cpu_buffer->commit_page->page->time_stamp = *ts;
 			/* try to discard, since we do not need this */
 			if (!rb_try_to_discard(cpu_buffer, event)) {
 				/* nope, just zero it */
@@ -1485,6 +1453,44 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
 	return ret;
 }
 
+static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+	local_inc(&cpu_buffer->committing);
+	local_inc(&cpu_buffer->commits);
+}
+
+static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+	unsigned long commits;
+
+	if (RB_WARN_ON(cpu_buffer,
+		       !local_read(&cpu_buffer->committing)))
+		return;
+
+ again:
+	commits = local_read(&cpu_buffer->commits);
+	/* synchronize with interrupts */
+	barrier();
+	if (local_read(&cpu_buffer->committing) == 1)
+		rb_set_commit_to_write(cpu_buffer);
+
+	local_dec(&cpu_buffer->committing);
+
+	/* synchronize with interrupts */
+	barrier();
+
+	/*
+	 * Need to account for interrupts coming in between the
+	 * updating of the commit page and the clearing of the
+	 * committing counter.
+	 */
+	if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
+	    !local_read(&cpu_buffer->committing)) {
+		local_inc(&cpu_buffer->committing);
+		goto again;
+	}
+}
+
 static struct ring_buffer_event *
 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 		      unsigned long length)
@@ -1494,6 +1500,8 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 	int commit = 0;
 	int nr_loops = 0;
 
+	rb_start_commit(cpu_buffer);
+
 	length = rb_calculate_event_length(length);
  again:
 	/*
@@ -1506,7 +1514,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 	 * Bail!
 	 */
 	if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
-		return NULL;
+		goto out_fail;
 
 	ts = rb_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
 
@@ -1537,7 +1545,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 
 			commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
 			if (commit == -EBUSY)
-				return NULL;
+				goto out_fail;
 
 			if (commit == -EAGAIN)
 				goto again;
@@ -1551,28 +1559,19 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 	if (unlikely(PTR_ERR(event) == -EAGAIN))
 		goto again;
 
-	if (!event) {
-		if (unlikely(commit))
-			/*
-			 * Ouch! We needed a timestamp and it was commited. But
-			 * we didn't get our event reserved.
-			 */
-			rb_set_commit_to_write(cpu_buffer);
-		return NULL;
-	}
+	if (!event)
+		goto out_fail;
 
-	/*
-	 * If the timestamp was commited, make the commit our entry
-	 * now so that we will update it when needed.
-	 */
-	if (unlikely(commit))
-		rb_set_commit_event(cpu_buffer, event);
-	else if (!rb_is_commit(cpu_buffer, event))
+	if (!rb_event_is_commit(cpu_buffer, event))
 		delta = 0;
 
 	event->time_delta = delta;
 
 	return event;
+
+ out_fail:
+	rb_end_commit(cpu_buffer);
+	return NULL;
 }
 
 #define TRACE_RECURSIVE_DEPTH 16
@@ -1682,13 +1681,14 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
 {
 	local_inc(&cpu_buffer->entries);
 
-	/* Only process further if we own the commit */
-	if (!rb_is_commit(cpu_buffer, event))
-		return;
-
-	cpu_buffer->write_stamp += event->time_delta;
+	/*
+	 * The event first in the commit queue updates the
+	 * time stamp.
+	 */
+	if (rb_event_is_commit(cpu_buffer, event))
+		cpu_buffer->write_stamp += event->time_delta;
 
-	rb_set_commit_to_write(cpu_buffer);
+	rb_end_commit(cpu_buffer);
 }
 
 /**
@@ -1777,15 +1777,15 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
 	/* The event is discarded regardless */
 	rb_event_discard(event);
 
+	cpu = smp_processor_id();
+	cpu_buffer = buffer->buffers[cpu];
+
 	/*
 	 * This must only be called if the event has not been
 	 * committed yet. Thus we can assume that preemption
 	 * is still disabled.
 	 */
-	RB_WARN_ON(buffer, preemptible());
-
-	cpu = smp_processor_id();
-	cpu_buffer = buffer->buffers[cpu];
+	RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
 
 	if (!rb_try_to_discard(cpu_buffer, event))
 		goto out;
@@ -1796,13 +1796,7 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
 	 */
 	local_inc(&cpu_buffer->entries);
  out:
-	/*
-	 * If a write came in and pushed the tail page
-	 * we still need to update the commit pointer
-	 * if we were the commit.
-	 */
-	if (rb_is_commit(cpu_buffer, event))
-		rb_set_commit_to_write(cpu_buffer);
+	rb_end_commit(cpu_buffer);
 
 	trace_recursive_unlock();
 
@@ -2720,6 +2714,8 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
 	cpu_buffer->overrun = 0;
 	cpu_buffer->read = 0;
 	local_set(&cpu_buffer->entries, 0);
+	local_set(&cpu_buffer->committing, 0);
+	local_set(&cpu_buffer->commits, 0);
 
 	cpu_buffer->write_stamp = 0;
 	cpu_buffer->read_stamp = 0;
-- 
cgit v1.2.3


From 57be88878e7aa38750384704d811485a607bbda4 Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Tue, 16 Jun 2009 16:39:12 +0800
Subject: tracing/filters: free filter_string in destroy_preds()

filter->filter_string is not freed when unloading a module:

 # insmod trace-events-sample.ko
 # echo "bar < 100" > /mnt/tracing/events/sample/foo_bar/filter
 # rmmod trace-events-sample.ko

[ Impact: fix memory leak when unloading module ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A375A30.9060802@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 1 +
 1 file changed, 1 insertion(+)

(limited to 'kernel')

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index b24ab0e6ea74..d9f01c1a042b 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -381,6 +381,7 @@ void destroy_preds(struct ftrace_event_call *call)
 			filter_free_pred(filter->preds[i]);
 	}
 	kfree(filter->preds);
+	kfree(filter->filter_string);
 	kfree(filter);
 	call->filter = NULL;
 }
-- 
cgit v1.2.3


From 00e95830a4d6e49f764fdb19896a89199bc0aa3b Mon Sep 17 00:00:00 2001
From: Li Zefan
Date: Tue, 16 Jun 2009 16:39:41 +0800
Subject: tracing/filters: fix race between filter setting and module unload

Module unload is protected by event_mutex, while setting filter is
protected by filter_mutex. This leads to the race:

echo 'bar == 0 || bar == 10' \    |
		> sample/filter   |
                                  |  insmod sample.ko
  add_pred("bar == 0")            |
    -> n_preds == 1               |
  add_pred("bar == 100")          |
    -> n_preds == 2               |
                                  |  rmmod sample.ko
                                  |  insmod sample.ko
  add_pred("&&")                  |
    -> n_preds == 1 (should be 3) |

Now event->filter->preds is corrupted. An then when filter_match_preds()
is called, the WARN_ON() in it will be triggered.

To avoid the race, we remove filter_mutex, and replace it with event_mutex.

[ Impact: prevent corruption of filters by module removing and loading ]

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A375A4D.6000205@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_events_filter.c | 27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index d9f01c1a042b..936c621bbf46 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -27,8 +27,6 @@
 #include "trace.h"
 #include "trace_output.h"
 
-static DEFINE_MUTEX(filter_mutex);
-
 enum filter_op_ids
 {
 	OP_OR,
@@ -294,12 +292,12 @@ void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s)
 {
 	struct event_filter *filter = call->filter;
 
-	mutex_lock(&filter_mutex);
+	mutex_lock(&event_mutex);
 	if (filter->filter_string)
 		trace_seq_printf(s, "%s\n", filter->filter_string);
 	else
 		trace_seq_printf(s, "none\n");
-	mutex_unlock(&filter_mutex);
+	mutex_unlock(&event_mutex);
 }
 
 void print_subsystem_event_filter(struct event_subsystem *system,
@@ -307,12 +305,12 @@ void print_subsystem_event_filter(struct event_subsystem *system,
 {
 	struct event_filter *filter = system->filter;
 
-	mutex_lock(&filter_mutex);
+	mutex_lock(&event_mutex);
 	if (filter->filter_string)
 		trace_seq_printf(s, "%s\n", filter->filter_string);
 	else
 		trace_seq_printf(s, "none\n");
-	mutex_unlock(&filter_mutex);
+	mutex_unlock(&event_mutex);
 }
 
 static struct ftrace_event_field *
@@ -434,7 +432,6 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
 		filter->n_preds = 0;
 	}
 
-	mutex_lock(&event_mutex);
 	list_for_each_entry(call, &ftrace_events, list) {
 		if (!call->define_fields)
 			continue;
@@ -444,7 +441,6 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
 			remove_filter_string(call->filter);
 		}
 	}
-	mutex_unlock(&event_mutex);
 }
 
 static int filter_add_pred_fn(struct filter_parse_state *ps,
@@ -631,7 +627,6 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
 	filter->preds[filter->n_preds] = pred;
 	filter->n_preds++;
 
-	mutex_lock(&event_mutex);
 	list_for_each_entry(call, &ftrace_events, list) {
 
 		if (!call->define_fields)
@@ -642,14 +637,12 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
 
 		err = filter_add_pred(ps, call, pred);
 		if (err) {
-			mutex_unlock(&event_mutex);
 			filter_free_subsystem_preds(system);
 			parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
 			goto out;
 		}
 		replace_filter_string(call->filter, filter_string);
 	}
-	mutex_unlock(&event_mutex);
 out:
 	return err;
 }
@@ -1076,12 +1069,12 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
 
 	struct filter_parse_state *ps;
 
-	mutex_lock(&filter_mutex);
+	mutex_lock(&event_mutex);
 
 	if (!strcmp(strstrip(filter_string), "0")) {
 		filter_disable_preds(call);
 		remove_filter_string(call->filter);
-		mutex_unlock(&filter_mutex);
+		mutex_unlock(&event_mutex);
 		return 0;
 	}
 
@@ -1109,7 +1102,7 @@ out:
 	postfix_clear(ps);
 	kfree(ps);
 out_unlock:
-	mutex_unlock(&filter_mutex);
+	mutex_unlock(&event_mutex);
 
 	return err;
 }
@@ -1121,12 +1114,12 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
 
 	struct filter_parse_state *ps;
 
-	mutex_lock(&filter_mutex);
+	mutex_lock(&event_mutex);
 
 	if (!strcmp(strstrip(filter_string), "0")) {
 		filter_free_subsystem_preds(system);
 		remove_filter_string(system->filter);
-		mutex_unlock(&filter_mutex);
+		mutex_unlock(&event_mutex);
 		return 0;
 	}
 
@@ -1154,7 +1147,7 @@ out:
 	postfix_clear(ps);
 	kfree(ps);
 out_unlock:
-	mutex_unlock(&filter_mutex);
+	mutex_unlock(&event_mutex);
 
 	return err;
 }
-- 
cgit v1.2.3


From 22f470f8daea64bc03be1fe30c8c5df382295386 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Thu, 11 Jun 2009 09:29:58 -0400
Subject: ring-buffer: use BUF_PAGE_HDR_SIZE in calculating index

The index of the event is found by masking PAGE_MASK to it and
subtracting the header size. Currently the header size is calculate
by PAGE_SIZE - BUF_PAGE_SIZE, when we already have a macro
BUF_PAGE_HDR_SIZE to define it.

If we want to change BUF_PAGE_SIZE to something less than filling
the rest of the page (this is done for debugging), then we break
the algorithm to find the index.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ed3559944fcf..6b17a11e42a2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1013,7 +1013,7 @@ rb_event_index(struct ring_buffer_event *event)
 {
 	unsigned long addr = (unsigned long)event;
 
-	return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
+	return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
 }
 
 static inline int
-- 
cgit v1.2.3


From c6a9d7b55e2df63de012a9a285bf2a0bee8e4d59 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Thu, 11 Jun 2009 09:49:15 -0400
Subject: ring-buffer: remove useless warn on check

A check if "write > BUF_PAGE_SIZE" is done right after a

	if (write > BUF_PAGE_SIZE)
		return ...;

Thus the check is actually testing the compiler and not the
kernel. This is useless, remove it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 3 ---
 1 file changed, 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 6b17a11e42a2..6cf340e1a4a3 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1334,9 +1334,6 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 
 	/* We reserved something on the buffer */
 
-	if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
-		return NULL;
-
 	event = __rb_page_index(tail_page, tail);
 	rb_update_event(event, type, length);
 
-- 
cgit v1.2.3


From 0dcd4d6c3e5b17ccf88d41cb354bb4d57cb18cbf Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Wed, 17 Jun 2009 14:03:44 -0400
Subject: ring-buffer: remove useless compile check for buffer_page size

The original version of the ring buffer had a hack to map the
page struct that held the pages of the buffer to also be the structure
that the ring buffer would keep the pages in a link list.

This overlap of the page struct was very dangerous and that hack was
removed a while ago.

But there was a check to make sure the buffer_page never became bigger
than the page struct, and would fail the compile if it did. The
check was only meaningful when we had the hack. Now that we have separate
allocated descriptors for the buffer pages, we can remove this check.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 11 -----------
 1 file changed, 11 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 6cf340e1a4a3..162da2305cbc 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -620,12 +620,6 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
 	kfree(cpu_buffer);
 }
 
-/*
- * Causes compile errors if the struct buffer_page gets bigger
- * than the struct page.
- */
-extern int ring_buffer_page_too_big(void);
-
 #ifdef CONFIG_HOTPLUG_CPU
 static int rb_cpu_notify(struct notifier_block *self,
 			 unsigned long action, void *hcpu);
@@ -648,11 +642,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	int bsize;
 	int cpu;
 
-	/* Paranoid! Optimizes out when all is well */
-	if (sizeof(struct buffer_page) > sizeof(struct page))
-		ring_buffer_page_too_big();
-
-
 	/* keep it in its own cache line */
 	buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
 			 GFP_KERNEL);
-- 
cgit v1.2.3


From 5f78abeebbf0a80975d719e11374535ca15396cb Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Wed, 17 Jun 2009 14:11:10 -0400
Subject: ring-buffer: check for less than two in size allocation

The ring buffer must have at least two pages allocated for the
reader page swap to work.

The page count check will miss the case of a zero size passed in.
Even though a zero size ring buffer would probably fail an allocation,
making the min size check for less than two instead of equal to one makes
the code a bit more robust.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 162da2305cbc..2e99dba6dc48 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -657,8 +657,8 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
 	buffer->reader_lock_key = key;
 
 	/* need at least two pages */
-	if (buffer->pages == 1)
-		buffer->pages++;
+	if (buffer->pages < 2)
+		buffer->pages = 2;
 
 	/*
 	 * In case of non-hotplug cpu, if the ring-buffer is allocated
-- 
cgit v1.2.3


From d47882078f05c2cb46b85f1e12a58ed9315b9d63 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Wed, 17 Jun 2009 00:39:43 -0400
Subject: ring-buffer: add locks around rb_per_cpu_empty

The checking of whether the buffer is empty or not needs to be serialized
among the readers. Add the reader spin lock around it.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2e99dba6dc48..969f7cbe8e93 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2756,12 +2756,17 @@ EXPORT_SYMBOL_GPL(ring_buffer_reset);
 int ring_buffer_empty(struct ring_buffer *buffer)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
+	unsigned long flags;
 	int cpu;
+	int ret;
 
 	/* yes this is racy, but if you don't like the race, lock the buffer */
 	for_each_buffer_cpu(buffer, cpu) {
 		cpu_buffer = buffer->buffers[cpu];
-		if (!rb_per_cpu_empty(cpu_buffer))
+		spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+		ret = rb_per_cpu_empty(cpu_buffer);
+		spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+		if (!ret)
 			return 0;
 	}
 
@@ -2777,14 +2782,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_empty);
 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
+	unsigned long flags;
 	int ret;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 1;
 
 	cpu_buffer = buffer->buffers[cpu];
+	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
 	ret = rb_per_cpu_empty(cpu_buffer);
-
+	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
 
 	return ret;
 }
-- 
cgit v1.2.3


From 8d707e8eb4de4b930573155ab4df4b3270ee25dd Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Tue, 16 Jun 2009 21:22:48 -0400
Subject: ring-buffer: do not grab locks in nmi

If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it
will need to read from the ring buffer. But the read side of the
ring buffer still takes locks. This patch adds a check on the read
side that if it is in an NMI, then it will disable the ring buffer
and not take any locks.

Reads can still happen on a disabled ring buffer.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer.c | 59 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 51 insertions(+), 8 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 969f7cbe8e93..589b3eedfa67 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2466,6 +2466,21 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
 }
 EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
 
+static inline int rb_ok_to_lock(void)
+{
+	/*
+	 * If an NMI die dumps out the content of the ring buffer
+	 * do not grab locks. We also permanently disable the ring
+	 * buffer too. A one time deal is all you get from reading
+	 * the ring buffer from an NMI.
+	 */
+	if (likely(!in_nmi() && !oops_in_progress))
+		return 1;
+
+	tracing_off_permanent();
+	return 0;
+}
+
 /**
  * ring_buffer_peek - peek at the next event to be read
  * @buffer: The ring buffer to read
@@ -2481,14 +2496,20 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
 	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
 	struct ring_buffer_event *event;
 	unsigned long flags;
+	int dolock;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return NULL;
 
+	dolock = rb_ok_to_lock();
  again:
-	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+	local_irq_save(flags);
+	if (dolock)
+		spin_lock(&cpu_buffer->reader_lock);
 	event = rb_buffer_peek(buffer, cpu, ts);
-	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+	if (dolock)
+		spin_unlock(&cpu_buffer->reader_lock);
+	local_irq_restore(flags);
 
 	if (event && event->type_len == RINGBUF_TYPE_PADDING) {
 		cpu_relax();
@@ -2540,6 +2561,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
 	struct ring_buffer_per_cpu *cpu_buffer;
 	struct ring_buffer_event *event = NULL;
 	unsigned long flags;
+	int dolock;
+
+	dolock = rb_ok_to_lock();
 
  again:
 	/* might be called in atomic */
@@ -2549,7 +2573,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
 		goto out;
 
 	cpu_buffer = buffer->buffers[cpu];
-	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+	local_irq_save(flags);
+	if (dolock)
+		spin_lock(&cpu_buffer->reader_lock);
 
 	event = rb_buffer_peek(buffer, cpu, ts);
 	if (!event)
@@ -2558,7 +2584,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
 	rb_advance_reader(cpu_buffer);
 
  out_unlock:
-	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+	if (dolock)
+		spin_unlock(&cpu_buffer->reader_lock);
+	local_irq_restore(flags);
 
  out:
 	preempt_enable();
@@ -2757,15 +2785,23 @@ int ring_buffer_empty(struct ring_buffer *buffer)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
 	unsigned long flags;
+	int dolock;
 	int cpu;
 	int ret;
 
+	dolock = rb_ok_to_lock();
+
 	/* yes this is racy, but if you don't like the race, lock the buffer */
 	for_each_buffer_cpu(buffer, cpu) {
 		cpu_buffer = buffer->buffers[cpu];
-		spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+		local_irq_save(flags);
+		if (dolock)
+			spin_lock(&cpu_buffer->reader_lock);
 		ret = rb_per_cpu_empty(cpu_buffer);
-		spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+		if (dolock)
+			spin_unlock(&cpu_buffer->reader_lock);
+		local_irq_restore(flags);
+
 		if (!ret)
 			return 0;
 	}
@@ -2783,15 +2819,22 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
 {
 	struct ring_buffer_per_cpu *cpu_buffer;
 	unsigned long flags;
+	int dolock;
 	int ret;
 
 	if (!cpumask_test_cpu(cpu, buffer->cpumask))
 		return 1;
 
+	dolock = rb_ok_to_lock();
+
 	cpu_buffer = buffer->buffers[cpu];
-	spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+	local_irq_save(flags);
+	if (dolock)
+		spin_lock(&cpu_buffer->reader_lock);
 	ret = rb_per_cpu_empty(cpu_buffer);
-	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+	if (dolock)
+		spin_unlock(&cpu_buffer->reader_lock);
+	local_irq_restore(flags);
 
 	return ret;
 }
-- 
cgit v1.2.3


From 4b221f0313f0f7f1f7aa0a1fd16ad400840def26 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Wed, 17 Jun 2009 17:01:09 -0400
Subject: ring-buffer: have benchmark test print to trace buffer

Currently the output of the ring buffer benchmark/test prints to
the console. This test runs for ten seconds every ten seconds and
ouputs the result after every iteration. This needlessly fills up
the logs.

This patch makes the ring buffer benchmark/test print to the ftrace
buffer using trace_printk. To view the test results, you must examine
the debug/tracing/trace file.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ring_buffer_benchmark.c | 37 ++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index cf6b0f50134e..573d3cc762c3 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -203,7 +203,7 @@ static void ring_buffer_producer(void)
 	 * Hammer the buffer for 10 secs (this may
 	 * make the system stall)
 	 */
-	pr_info("Starting ring buffer hammer\n");
+	trace_printk("Starting ring buffer hammer\n");
 	do_gettimeofday(&start_tv);
 	do {
 		struct ring_buffer_event *event;
@@ -239,7 +239,7 @@ static void ring_buffer_producer(void)
 #endif
 
 	} while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
-	pr_info("End ring buffer hammer\n");
+	trace_printk("End ring buffer hammer\n");
 
 	if (consumer) {
 		/* Init both completions here to avoid races */
@@ -262,49 +262,50 @@ static void ring_buffer_producer(void)
 	overruns = ring_buffer_overruns(buffer);
 
 	if (kill_test)
-		pr_info("ERROR!\n");
-	pr_info("Time:     %lld (usecs)\n", time);
-	pr_info("Overruns: %lld\n", overruns);
+		trace_printk("ERROR!\n");
+	trace_printk("Time:     %lld (usecs)\n", time);
+	trace_printk("Overruns: %lld\n", overruns);
 	if (disable_reader)
-		pr_info("Read:     (reader disabled)\n");
+		trace_printk("Read:     (reader disabled)\n");
 	else
-		pr_info("Read:     %ld  (by %s)\n", read,
+		trace_printk("Read:     %ld  (by %s)\n", read,
 			read_events ? "events" : "pages");
-	pr_info("Entries:  %lld\n", entries);
-	pr_info("Total:    %lld\n", entries + overruns + read);
-	pr_info("Missed:   %ld\n", missed);
-	pr_info("Hit:      %ld\n", hit);
+	trace_printk("Entries:  %lld\n", entries);
+	trace_printk("Total:    %lld\n", entries + overruns + read);
+	trace_printk("Missed:   %ld\n", missed);
+	trace_printk("Hit:      %ld\n", hit);
 
 	/* Convert time from usecs to millisecs */
 	do_div(time, USEC_PER_MSEC);
 	if (time)
 		hit /= (long)time;
 	else
-		pr_info("TIME IS ZERO??\n");
+		trace_printk("TIME IS ZERO??\n");
 
-	pr_info("Entries per millisec: %ld\n", hit);
+	trace_printk("Entries per millisec: %ld\n", hit);
 
 	if (hit) {
 		/* Calculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / hit;
-		pr_info("%ld ns per entry\n", avg);
+		trace_printk("%ld ns per entry\n", avg);
 	}
 
 	if (missed) {
 		if (time)
 			missed /= (long)time;
 
-		pr_info("Total iterations per millisec: %ld\n", hit + missed);
+		trace_printk("Total iterations per millisec: %ld\n",
+			     hit + missed);
 
 		/* it is possible that hit + missed will overflow and be zero */
 		if (!(hit + missed)) {
-			pr_info("hit + missed overflowed and totalled zero!\n");
+			trace_printk("hit + missed overflowed and totalled zero!\n");
 			hit--; /* make it non zero */
 		}
 
 		/* Caculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / (hit + missed);
-		pr_info("%ld ns per entry\n", avg);
+		trace_printk("%ld ns per entry\n", avg);
 	}
 }
 
@@ -355,7 +356,7 @@ static int ring_buffer_producer_thread(void *arg)
 
 		ring_buffer_producer();
 
-		pr_info("Sleeping for 10 secs\n");
+		trace_printk("Sleeping for 10 secs\n");
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(HZ * SLEEP_TIME);
 		__set_current_state(TASK_RUNNING);
-- 
cgit v1.2.3


From eb4a03780d4c4464ef2ad86d80cca3f3284fe81d Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Thu, 18 Jun 2009 12:53:21 -0400
Subject: function-graph: disable when both x86_32 and optimize for size are
 configured

On x86_32, when optimize for size is set, gcc may align the frame pointer
and make a copy of the the return address inside the stack frame.
The return address that is located in the stack frame may not be
the one used to return to the calling function. This will break the
function graph tracer.

The function graph tracer replaces the return address with a jump to a hook
function that can trace the exit of the function. If it only replaces
a copy, then the hook will not be called when the function returns.
Worse yet, when the parent function returns, the function graph tracer
will return back to the location of the child function which will
easily crash the kernel with weird results.

To see the problem, when i386 is compiled with -Os we get:

c106be03:       57                      push   %edi
c106be04:       8d 7c 24 08             lea    0x8(%esp),%edi
c106be08:       83 e4 e0                and    $0xffffffe0,%esp
c106be0b:       ff 77 fc                pushl  0xfffffffc(%edi)
c106be0e:       55                      push   %ebp
c106be0f:       89 e5                   mov    %esp,%ebp
c106be11:       57                      push   %edi
c106be12:       56                      push   %esi
c106be13:       53                      push   %ebx
c106be14:       81 ec 8c 00 00 00       sub    $0x8c,%esp
c106be1a:       e8 f5 57 fb ff          call   c1021614 <mcount>

When it is compiled with -O2 instead we get:

c10896f0:       55                      push   %ebp
c10896f1:       89 e5                   mov    %esp,%ebp
c10896f3:       83 ec 28                sub    $0x28,%esp
c10896f6:       89 5d f4                mov    %ebx,0xfffffff4(%ebp)
c10896f9:       89 75 f8                mov    %esi,0xfffffff8(%ebp)
c10896fc:       89 7d fc                mov    %edi,0xfffffffc(%ebp)
c10896ff:       e8 d0 08 fa ff          call   c1029fd4 <mcount>

The compile with -Os will align the stack pointer then set up the
frame pointer (%ebp), and it copies the return address back into
the stack frame. The change to the return address in mcount is done
to the copy and not the real place holder of the return address.

Then compile with -O2 sets up the frame pointer first, this makes
the change to the return address by mcount affect where the function
will jump on exit.

Reported-by: Jake Edge <jake@lwn.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/Kconfig | 1 +
 1 file changed, 1 insertion(+)

(limited to 'kernel')

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 4a13e5a01ce3..1eac85253ce9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -121,6 +121,7 @@ config FUNCTION_GRAPH_TRACER
 	bool "Kernel Function Graph Tracer"
 	depends on HAVE_FUNCTION_GRAPH_TRACER
 	depends on FUNCTION_TRACER
+	depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
 	default y
 	help
 	  Enable the kernel to trace a function at both its return
-- 
cgit v1.2.3


From 71e308a239c098673570d0b417d42262bb535909 Mon Sep 17 00:00:00 2001
From: Steven Rostedt
Date: Thu, 18 Jun 2009 12:45:08 -0400
Subject: function-graph: add stack frame test

In case gcc does something funny with the stack frames, or the return
from function code, we would like to detect that.

An arch may implement passing of a variable that is unique to the
function and can be saved on entering a function and can be tested
when exiting the function. Usually the frame pointer can be used for
this purpose.

This patch also implements this for x86. Where it passes in the stack
frame of the parent function, and will test that frame on exit.

There was a case in x86_32 with optimize for size (-Os) where, for a
few functions, gcc would align the stack frame and place a copy of the
return address into it. The function graph tracer modified the copy and
not the actual return address. On return from the funtion, it did not go
to the tracer hook, but returned to the parent. This broke the function
graph tracer, because the return of the parent (where gcc did not do
this funky manipulation) returned to the location that the child function
was suppose to. This caused strange kernel crashes.

This test detected the problem and pointed out where the issue was.

This modifies the parameters of one of the functions that the arch
specific code calls, so it includes changes to arch code to accommodate
the new prototype.

Note, I notice that the parsic arch implements its own push_return_trace.
This is now a generic function and the ftrace_push_return_trace should be
used instead. This patch does not touch that code.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/powerpc/kernel/ftrace.c         |  2 +-
 arch/s390/kernel/ftrace.c            |  2 +-
 arch/x86/Kconfig                     |  1 +
 arch/x86/kernel/entry_32.S           |  2 ++
 arch/x86/kernel/entry_64.S           |  2 ++
 arch/x86/kernel/ftrace.c             |  6 ++++--
 include/linux/ftrace.h               |  4 +++-
 kernel/trace/Kconfig                 |  7 +++++++
 kernel/trace/trace_functions_graph.c | 36 ++++++++++++++++++++++++++++++++----
 9 files changed, 53 insertions(+), 9 deletions(-)

(limited to 'kernel')

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 2d182f119d1d..58d6a6109040 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -605,7 +605,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		return;
 	}
 
-	if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
+	if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) {
 		*parent = old;
 		return;
 	}
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 82ddfd3a75af..3e298e64f0db 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -190,7 +190,7 @@ unsigned long prepare_ftrace_return(unsigned long ip, unsigned long parent)
 		goto out;
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		goto out;
-	if (ftrace_push_return_trace(parent, ip, &trace.depth) == -EBUSY)
+	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
 		goto out;
 	trace.func = ftrace_mcount_call_adjust(ip) & PSW_ADDR_INSN;
 	/* Only trace if the calling function expects to. */
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 356d2ec8e2fb..fcf12af07427 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -33,6 +33,7 @@ config X86
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
+	select HAVE_FUNCTION_GRAPH_FP_TEST
 	select HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
 	select HAVE_FTRACE_SYSCALLS
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index c929add475c9..0d4b28564c14 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1154,6 +1154,7 @@ ENTRY(ftrace_graph_caller)
 	pushl %edx
 	movl 0xc(%esp), %edx
 	lea 0x4(%ebp), %eax
+	movl (%ebp), %ecx
 	subl $MCOUNT_INSN_SIZE, %edx
 	call prepare_ftrace_return
 	popl %edx
@@ -1168,6 +1169,7 @@ return_to_handler:
 	pushl %eax
 	pushl %ecx
 	pushl %edx
+	movl %ebp, %eax
 	call ftrace_return_to_handler
 	movl %eax, 0xc(%esp)
 	popl %edx
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index de74f0a3e0ed..c251be745107 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -135,6 +135,7 @@ ENTRY(ftrace_graph_caller)
 
 	leaq 8(%rbp), %rdi
 	movq 0x38(%rsp), %rsi
+	movq (%rbp), %rdx
 	subq $MCOUNT_INSN_SIZE, %rsi
 
 	call	prepare_ftrace_return
@@ -150,6 +151,7 @@ GLOBAL(return_to_handler)
 	/* Save the return values */
 	movq %rax, (%rsp)
 	movq %rdx, 8(%rsp)
+	movq %rbp, %rdi
 
 	call ftrace_return_to_handler
 
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index b79c5533c421..d94e1ea3b9fe 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -408,7 +408,8 @@ int ftrace_disable_ftrace_graph_caller(void)
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
  */
-void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+			   unsigned long frame_pointer)
 {
 	unsigned long old;
 	int faulted;
@@ -453,7 +454,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		return;
 	}
 
-	if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
+	if (ftrace_push_return_trace(old, self_addr, &trace.depth,
+		    frame_pointer) == -EBUSY) {
 		*parent = old;
 		return;
 	}
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 39b95c56587e..dc3b1328aaeb 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -362,6 +362,7 @@ struct ftrace_ret_stack {
 	unsigned long func;
 	unsigned long long calltime;
 	unsigned long long subtime;
+	unsigned long fp;
 };
 
 /*
@@ -372,7 +373,8 @@ struct ftrace_ret_stack {
 extern void return_to_handler(void);
 
 extern int
-ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth);
+ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
+			 unsigned long frame_pointer);
 
 /*
  * Sometimes we don't want to trace a function with the function
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 1eac85253ce9..b17ed8787ded 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -18,6 +18,13 @@ config HAVE_FUNCTION_TRACER
 config HAVE_FUNCTION_GRAPH_TRACER
 	bool
 
+config HAVE_FUNCTION_GRAPH_FP_TEST
+	bool
+	help
+	 An arch may pass in a unique value (frame pointer) to both the
+	 entering and exiting of a function. On exit, the value is compared
+	 and if it does not match, then it will panic the kernel.
+
 config HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	bool
 	help
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 8b592418d8b2..d2249abafb53 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -57,7 +57,8 @@ static struct tracer_flags tracer_flags = {
 
 /* Add a function return address to the trace stack on thread info.*/
 int
-ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
+ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
+			 unsigned long frame_pointer)
 {
 	unsigned long long calltime;
 	int index;
@@ -85,6 +86,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
 	current->ret_stack[index].subtime = 0;
+	current->ret_stack[index].fp = frame_pointer;
 	*depth = index;
 
 	return 0;
@@ -92,7 +94,8 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
 
 /* Retrieve a function return address to the trace stack on thread info.*/
 static void
-ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
+ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
+			unsigned long frame_pointer)
 {
 	int index;
 
@@ -106,6 +109,31 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
 		return;
 	}
 
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+	/*
+	 * The arch may choose to record the frame pointer used
+	 * and check it here to make sure that it is what we expect it
+	 * to be. If gcc does not set the place holder of the return
+	 * address in the frame pointer, and does a copy instead, then
+	 * the function graph trace will fail. This test detects this
+	 * case.
+	 *
+	 * Currently, x86_32 with optimize for size (-Os) makes the latest
+	 * gcc do the above.
+	 */
+	if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
+		ftrace_graph_stop();
+		WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
+		     "  from func %pF return to %lx\n",
+		     current->ret_stack[index].fp,
+		     frame_pointer,
+		     (void *)current->ret_stack[index].func,
+		     current->ret_stack[index].ret);
+		*ret = (unsigned long)panic;
+		return;
+	}
+#endif
+
 	*ret = current->ret_stack[index].ret;
 	trace->func = current->ret_stack[index].func;
 	trace->calltime = current->ret_stack[index].calltime;
@@ -117,12 +145,12 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
  * Send the trace to the ring-buffer.
  * @return the original return address.
  */
-unsigned long ftrace_return_to_handler(void)
+unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 {
 	struct ftrace_graph_ret trace;
 	unsigned long ret;
 
-	ftrace_pop_return_trace(&trace, &ret);
+	ftrace_pop_return_trace(&trace, &ret, frame_pointer);
 	trace.rettime = trace_clock_local();
 	ftrace_graph_return(&trace);
 	barrier();
-- 
cgit v1.2.3


From c85a17e22695969aa24a7ffa40cf26d6e6fcfd50 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker
Date: Sat, 20 Jun 2009 05:45:14 +0200
Subject: tracing/urgent: fix unbalanced ftrace_start_up

Perfcounter reports the following stats for a wide system
profiling:

 #
 # (2364 samples)
 #
 # Overhead  Symbol
 # ........  ......
 #
    15.40%  [k] mwait_idle_with_hints
     8.29%  [k] read_hpet
     5.75%  [k] ftrace_caller
     3.60%  [k] ftrace_call
     [...]

This snapshot has been taken while neither the function tracer nor
the function graph tracer was running.
With dynamic ftrace, such results show a wrong ftrace behaviour
because all calls to ftrace_caller or ftrace_graph_caller (the patched
calls to mcount) are supposed to be patched into nop if none of those
tracers are running.

The problem occurs after the first run of the function tracer. Once we
launch it a second time, the callsites will never be nopped back,
unless you set custom filters.
For example it happens during the self tests at boot time.
The function tracer selftest runs, and then the dynamic tracing is
tested too. After that, the callsites are left un-nopped.

This is because the reset callback of the function tracer tries to
unregister two ftrace callbacks in once: the common function tracer
and the function tracer with stack backtrace, regardless of which
one is currently in use.
It then creates an unbalance on ftrace_start_up value which is expected
to be zero when the last ftrace callback is unregistered. When it
reaches zero, the FTRACE_DISABLE_CALLS is set on the next ftrace
command, triggering the patching into nop. But since it becomes
unbalanced, ie becomes lower than zero, if the kernel functions
are patched again (as in every further function tracer runs), they
won't ever be nopped back.

Note that ftrace_call and ftrace_graph_call are still patched back
to ftrace_stub in the off case, but not the callers of ftrace_call
and ftrace_graph_caller. It means that the tracing is well deactivated
but we waste a useless call into every kernel function.

This patch just unregisters the right ftrace_ops for the function
tracer on its reset callback and ignores the other one which is
not registered, fixing the unbalance. The problem also happens
is .30

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@kernel.org
---
 kernel/trace/trace_functions.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

(limited to 'kernel')

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index c9a0b7df44ff..90f134764837 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -193,9 +193,11 @@ static void tracing_start_function_trace(void)
 static void tracing_stop_function_trace(void)
 {
 	ftrace_function_enabled = 0;
-	/* OK if they are not registered */
-	unregister_ftrace_function(&trace_stack_ops);
-	unregister_ftrace_function(&trace_ops);
+
+	if (func_flags.val & TRACE_FUNC_OPT_STACK)
+		unregister_ftrace_function(&trace_stack_ops);
+	else
+		unregister_ftrace_function(&trace_ops);
 }
 
 static int func_set_flag(u32 old_flags, u32 bit, int set)
-- 
cgit v1.2.3


From 9ea1a153a4fb435c22e9988784bb476671286112 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker
Date: Sat, 20 Jun 2009 06:52:21 +0200
Subject: tracing/urgent: warn in case of ftrace_start_up inbalance

Prevent from further ftrace_start_up inbalances so that we avoid
future nop patching omissions with dynamic ftrace.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'kernel')

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bb60732ade0c..3718d55fb4c3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1224,6 +1224,13 @@ static void ftrace_shutdown(int command)
 		return;
 
 	ftrace_start_up--;
+	/*
+	 * Just warn in case of unbalance, no need to kill ftrace, it's not
+	 * critical but the ftrace_call callers may be never nopped again after
+	 * further ftrace uses.
+	 */
+	WARN_ON_ONCE(ftrace_start_up < 0);
+
 	if (!ftrace_start_up)
 		command |= FTRACE_DISABLE_CALLS;
 
-- 
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