| Age | Commit message (Collapse) | Author |
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commit 5f98fd034ca6fd1ab8c91a3488968a0e9caaabf6 upstream.
Since the actual slab freeing is deferred when calling kvfree_rcu(), so
is the kmemleak_free() callback informing kmemleak of the object
deletion. From the perspective of the kvfree_rcu() caller, the object is
freed and it may remove any references to it. Since kmemleak does not
scan RCU internal data storing the pointer, it will report such objects
as leaks during the grace period.
Tell kmemleak to ignore such objects on the kvfree_call_rcu() path. Note
that the tiny RCU implementation does not have such issue since the
objects can be tracked from the rcu_ctrlblk structure.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://lore.kernel.org/all/F903A825-F05F-4B77-A2B5-7356282FBA2C@apple.com/
Cc: <stable@vger.kernel.org>
Tested-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit b96e7a5fa0ba9cda32888e04f8f4bac42d49a7f8 upstream.
There are instances where rcu_cpu_stall_reset() is called when jiffies
did not get a chance to update for a long time. Before jiffies is
updated, the CPU stall detector can go off triggering false-positives
where a just-started grace period appears to be ages old. In the past,
we disabled stall detection in rcu_cpu_stall_reset() however this got
changed [1]. This is resulting in false-positives in KGDB usecase [2].
Fix this by deferring the update of jiffies to the third run of the FQS
loop. This is more robust, as, even if rcu_cpu_stall_reset() is called
just before jiffies is read, we would end up pushing out the jiffies
read by 3 more FQS loops. Meanwhile the CPU stall detection will be
delayed and we will not get any false positives.
[1] https://lore.kernel.org/all/20210521155624.174524-2-senozhatsky@chromium.org/
[2] https://lore.kernel.org/all/20230814020045.51950-2-chenhuacai@loongson.cn/
Tested with rcutorture.cpu_stall option as well to verify stall behavior
with/without patch.
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Reported-by: Binbin Zhou <zhoubinbin@loongson.cn>
Closes: https://lore.kernel.org/all/20230814020045.51950-2-chenhuacai@loongson.cn/
Suggested-by: Paul McKenney <paulmck@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: a80be428fbc1 ("rcu: Do not disable GP stall detection in rcu_cpu_stall_reset()")
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit 401b0de3ae4fa49d1014c8941e26d9a25f37e7cf ]
The rcu_tasks_invoke_cbs() function relies on queue_work_on() to silently
fall back to WORK_CPU_UNBOUND when the specified CPU is offline. However,
the queue_work_on() function's silent fallback mechanism relies on that
CPU having been online at some time in the past. When queue_work_on()
is passed a CPU that has never been online, workqueue lockups ensue,
which can be bad for your kernel's general health and well-being.
This commit therefore checks whether a given CPU has ever been online,
and, if not substitutes WORK_CPU_UNBOUND in the subsequent call to
queue_work_on(). Why not simply omit the queue_work_on() call entirely?
Because this function is flooding callback-invocation notifications
to all CPUs, and must deal with possibilities that include a sparse
cpu_possible_mask.
This commit also moves the setting of the rcu_data structure's
->beenonline field to rcu_cpu_starting(), which executes on the
incoming CPU before that CPU has ever enabled interrupts. This ensures
that the required workqueues are present. In addition, because the
incoming CPU has not yet enabled its interrupts, there cannot yet have
been any softirq handlers running on this CPU, which means that the
WARN_ON_ONCE(!rdp->beenonline) within the RCU_SOFTIRQ handler cannot
have triggered yet.
Fixes: d363f833c6d88 ("rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations")
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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[ Upstream commit 15d44dfa40305da1648de4bf001e91cc63148725 ]
Currently, rcu_cpu_starting() is written so that it might be invoked
with interrupts enabled. However, it is always called when interrupts
are disabled, either by rcu_init(), notify_cpu_starting(), or from a
call point prior to the call to notify_cpu_starting().
But why bother requiring that interrupts be disabled? The purpose is
to allow the rcu_data structure's ->beenonline flag to be set after all
early processing has completed for the incoming CPU, thus allowing this
flag to be used to determine when workqueues have been set up for the
incoming CPU, while still allowing this flag to be used as a diagnostic
within rcu_core().
This commit therefore makes rcu_cpu_starting() rely on interrupts being
disabled.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Stable-dep-of: 401b0de3ae4f ("rcu-tasks: Stop rcu_tasks_invoke_cbs() from using never-onlined CPUs")
Signed-off-by: Sasha Levin <sashal@kernel.org>
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commit 5da7cb193db32da783a3f3e77d8b639989321d48 upstream.
Memory passed to kvfree_rcu() that is to be freed is tracked by a
per-CPU kfree_rcu_cpu structure, which in turn contains pointers
to kvfree_rcu_bulk_data structures that contain pointers to memory
that has not yet been handed to RCU, along with an kfree_rcu_cpu_work
structure that tracks the memory that has already been handed to RCU.
These structures track three categories of memory: (1) Memory for
kfree(), (2) Memory for kvfree(), and (3) Memory for both that arrived
during an OOM episode. The first two categories are tracked in a
cache-friendly manner involving a dynamically allocated page of pointers
(the aforementioned kvfree_rcu_bulk_data structures), while the third
uses a simple (but decidedly cache-unfriendly) linked list through the
rcu_head structures in each block of memory.
On a given CPU, these three categories are handled as a unit, with that
CPU's kfree_rcu_cpu_work structure having one pointer for each of the
three categories. Clearly, new memory for a given category cannot be
placed in the corresponding kfree_rcu_cpu_work structure until any old
memory has had its grace period elapse and thus has been removed. And
the kfree_rcu_monitor() function does in fact check for this.
Except that the kfree_rcu_monitor() function checks these pointers one
at a time. This means that if the previous kfree_rcu() memory passed
to RCU had only category 1 and the current one has only category 2, the
kfree_rcu_monitor() function will send that current category-2 memory
along immediately. This can result in memory being freed too soon,
that is, out from under unsuspecting RCU readers.
To see this, consider the following sequence of events, in which:
o Task A on CPU 0 calls rcu_read_lock(), then uses "from_cset",
then is preempted.
o CPU 1 calls kfree_rcu(cset, rcu_head) in order to free "from_cset"
after a later grace period. Except that "from_cset" is freed
right after the previous grace period ended, so that "from_cset"
is immediately freed. Task A resumes and references "from_cset"'s
member, after which nothing good happens.
In full detail:
CPU 0 CPU 1
---------------------- ----------------------
count_memcg_event_mm()
|rcu_read_lock() <---
|mem_cgroup_from_task()
|// css_set_ptr is the "from_cset" mentioned on CPU 1
|css_set_ptr = rcu_dereference((task)->cgroups)
|// Hard irq comes, current task is scheduled out.
cgroup_attach_task()
|cgroup_migrate()
|cgroup_migrate_execute()
|css_set_move_task(task, from_cset, to_cset, true)
|cgroup_move_task(task, to_cset)
|rcu_assign_pointer(.., to_cset)
|...
|cgroup_migrate_finish()
|put_css_set_locked(from_cset)
|from_cset->refcount return 0
|kfree_rcu(cset, rcu_head) // free from_cset after new gp
|add_ptr_to_bulk_krc_lock()
|schedule_delayed_work(&krcp->monitor_work, ..)
kfree_rcu_monitor()
|krcp->bulk_head[0]'s work attached to krwp->bulk_head_free[]
|queue_rcu_work(system_wq, &krwp->rcu_work)
|if rwork->rcu.work is not in WORK_STRUCT_PENDING_BIT state,
|call_rcu(&rwork->rcu, rcu_work_rcufn) <--- request new gp
// There is a perious call_rcu(.., rcu_work_rcufn)
// gp end, rcu_work_rcufn() is called.
rcu_work_rcufn()
|__queue_work(.., rwork->wq, &rwork->work);
|kfree_rcu_work()
|krwp->bulk_head_free[0] bulk is freed before new gp end!!!
|The "from_cset" is freed before new gp end.
// the task resumes some time later.
|css_set_ptr->subsys[(subsys_id) <--- Caused kernel crash, because css_set_ptr is freed.
This commit therefore causes kfree_rcu_monitor() to refrain from moving
kfree_rcu() memory to the kfree_rcu_cpu_work structure until the RCU
grace period has completed for all three categories.
v2: Use helper function instead of inserted code block at kfree_rcu_monitor().
Fixes: 34c881745549 ("rcu: Support kfree_bulk() interface in kfree_rcu()")
Fixes: 5f3c8d620447 ("rcu/tree: Maintain separate array for vmalloc ptrs")
Reported-by: Mukesh Ojha <quic_mojha@quicinc.com>
Signed-off-by: Ziwei Dai <ziwei.dai@unisoc.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Tested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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commit 7a29fb4a4771124bc61de397dbfc1554dbbcc19c upstream.
Registering a kprobe on __rcu_irq_enter_check_tick() can cause kernel
stack overflow as shown below. This issue can be reproduced by enabling
CONFIG_NO_HZ_FULL and booting the kernel with argument "nohz_full=",
and then giving the following commands at the shell prompt:
# cd /sys/kernel/tracing/
# echo 'p:mp1 __rcu_irq_enter_check_tick' >> kprobe_events
# echo 1 > events/kprobes/enable
This commit therefore adds __rcu_irq_enter_check_tick() to the kprobes
blacklist using NOKPROBE_SYMBOL().
Insufficient stack space to handle exception!
ESR: 0x00000000f2000004 -- BRK (AArch64)
FAR: 0x0000ffffccf3e510
Task stack: [0xffff80000ad30000..0xffff80000ad38000]
IRQ stack: [0xffff800008050000..0xffff800008058000]
Overflow stack: [0xffff089c36f9f310..0xffff089c36fa0310]
CPU: 5 PID: 190 Comm: bash Not tainted 6.2.0-rc2-00320-g1f5abbd77e2c #19
Hardware name: linux,dummy-virt (DT)
pstate: 400003c5 (nZcv DAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __rcu_irq_enter_check_tick+0x0/0x1b8
lr : ct_nmi_enter+0x11c/0x138
sp : ffff80000ad30080
x29: ffff80000ad30080 x28: ffff089c82e20000 x27: 0000000000000000
x26: 0000000000000000 x25: ffff089c02a8d100 x24: 0000000000000000
x23: 00000000400003c5 x22: 0000ffffccf3e510 x21: ffff089c36fae148
x20: ffff80000ad30120 x19: ffffa8da8fcce148 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: ffffa8da8e44ea6c
x14: ffffa8da8e44e968 x13: ffffa8da8e03136c x12: 1fffe113804d6809
x11: ffff6113804d6809 x10: 0000000000000a60 x9 : dfff800000000000
x8 : ffff089c026b404f x7 : 00009eec7fb297f7 x6 : 0000000000000001
x5 : ffff80000ad30120 x4 : dfff800000000000 x3 : ffffa8da8e3016f4
x2 : 0000000000000003 x1 : 0000000000000000 x0 : 0000000000000000
Kernel panic - not syncing: kernel stack overflow
CPU: 5 PID: 190 Comm: bash Not tainted 6.2.0-rc2-00320-g1f5abbd77e2c #19
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0xf8/0x108
show_stack+0x20/0x30
dump_stack_lvl+0x68/0x84
dump_stack+0x1c/0x38
panic+0x214/0x404
add_taint+0x0/0xf8
panic_bad_stack+0x144/0x160
handle_bad_stack+0x38/0x58
__bad_stack+0x78/0x7c
__rcu_irq_enter_check_tick+0x0/0x1b8
arm64_enter_el1_dbg.isra.0+0x14/0x20
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
arm64_enter_el1_dbg.isra.0+0x14/0x20
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
arm64_enter_el1_dbg.isra.0+0x14/0x20
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
[...]
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
arm64_enter_el1_dbg.isra.0+0x14/0x20
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
arm64_enter_el1_dbg.isra.0+0x14/0x20
el1_dbg+0x2c/0x90
el1h_64_sync_handler+0xcc/0xe8
el1h_64_sync+0x64/0x68
__rcu_irq_enter_check_tick+0x0/0x1b8
el1_interrupt+0x28/0x60
el1h_64_irq_handler+0x18/0x28
el1h_64_irq+0x64/0x68
__ftrace_set_clr_event_nolock+0x98/0x198
__ftrace_set_clr_event+0x58/0x80
system_enable_write+0x144/0x178
vfs_write+0x174/0x738
ksys_write+0xd0/0x188
__arm64_sys_write+0x4c/0x60
invoke_syscall+0x64/0x180
el0_svc_common.constprop.0+0x84/0x160
do_el0_svc+0x48/0xe8
el0_svc+0x34/0xd0
el0t_64_sync_handler+0xb8/0xc0
el0t_64_sync+0x190/0x194
SMP: stopping secondary CPUs
Kernel Offset: 0x28da86000000 from 0xffff800008000000
PHYS_OFFSET: 0xfffff76600000000
CPU features: 0x00000,01a00100,0000421b
Memory Limit: none
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Link: https://lore.kernel.org/all/20221119040049.795065-1-zhengyejian1@huawei.com/
Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[ Upstream commit ceb1c8c9b8aa9199da46a0f29d2d5f08d9b44c15 ]
Running rcutorture with non-zero fqs_duration module parameter in a
kernel built with CONFIG_PREEMPTION=y results in the following splat:
BUG: using __this_cpu_read() in preemptible [00000000]
code: rcu_torture_fqs/398
caller is __this_cpu_preempt_check+0x13/0x20
CPU: 3 PID: 398 Comm: rcu_torture_fqs Not tainted 6.0.0-rc1-yoctodev-standard+
Call Trace:
<TASK>
dump_stack_lvl+0x5b/0x86
dump_stack+0x10/0x16
check_preemption_disabled+0xe5/0xf0
__this_cpu_preempt_check+0x13/0x20
rcu_force_quiescent_state.part.0+0x1c/0x170
rcu_force_quiescent_state+0x1e/0x30
rcu_torture_fqs+0xca/0x160
? rcu_torture_boost+0x430/0x430
kthread+0x192/0x1d0
? kthread_complete_and_exit+0x30/0x30
ret_from_fork+0x22/0x30
</TASK>
The problem is that rcu_force_quiescent_state() uses __this_cpu_read()
in preemptible code instead of the proper raw_cpu_read(). This commit
therefore changes __this_cpu_read() to raw_cpu_read().
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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Making polled RCU grace periods account for expedited grace periods
required acquiring the leaf rcu_node structure's lock during early boot,
but after rcu_init() was called. This lock is irq-disabled, but the
code incorrectly assumes that irqs are always disabled when invoking
synchronize_rcu(). The exception is early boot before the scheduler has
started, which means that upon return from synchronize_rcu(), irqs will
be incorrectly enabled.
This commit fixes this bug by using irqsave/irqrestore locking primitives.
Fixes: bf95b2bc3e42 ("rcu: Switch polled grace-period APIs to ->gp_seq_polled")
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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'nocb.2022.09.01a', 'poll.2022.08.31b', 'poll-srcu.2022.08.31b' and 'tasks.2022.08.31b' into HEAD
doc.2022.08.31b: Documentation updates
fixes.2022.08.31b: Miscellaneous fixes
kvfree.2022.08.31b: kvfree_rcu() updates
nocb.2022.09.01a: NOCB CPU updates
poll.2022.08.31b: Full-oldstate RCU polling grace-period API
poll-srcu.2022.08.31b: Polled SRCU grace-period updates
tasks.2022.08.31b: Tasks RCU updates
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Userspace execution is a valid quiescent state for RCU Tasks Trace,
but the scheduling-clock interrupt does not currently report such
quiescent states.
Of course, the scheduling-clock interrupt is not strictly speaking
userspace execution. However, the only way that this code is not
in a quiescent state is if something invoked rcu_read_lock_trace(),
and that would be reflected in the ->trc_reader_nesting field in
the task_struct structure. Furthermore, this field is checked by
rcu_tasks_trace_qs(), which is invoked by rcu_tasks_qs() which is in
turn invoked by rcu_note_voluntary_context_switch() in kernels building
at least one of the RCU Tasks flavors. It is therefore safe to invoke
rcu_tasks_trace_qs() from the rcu_sched_clock_irq().
But rcu_tasks_qs() also invokes rcu_tasks_classic_qs() for RCU
Tasks, which lacks the read-side markers provided by RCU Tasks Trace.
This raises the possibility that an RCU Tasks grace period could start
after the interrupt from userspace execution, but before the call to
rcu_sched_clock_irq(). However, it turns out that this is safe because
the RCU Tasks grace period waits for an RCU grace period, which will
wait for the entire scheduling-clock interrupt handler, including any
RCU Tasks read-side critical section that this handler might contain.
This commit therefore updates the rcu_sched_clock_irq() function's
check for usermode execution and its call to rcu_tasks_classic_qs()
to instead check for both usermode execution and interrupt from idle,
and to instead call rcu_note_voluntary_context_switch(). This
consolidates code and provides more faster RCU Tasks Trace
reporting of quiescent states in kernels that do scheduling-clock
interrupts for userspace execution.
[ paulmck: Consolidate checks into rcu_sched_clock_irq(). ]
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Large systems can have hundreds of rcu_node structures, and updating
counters in each of them might slow down booting. This commit therefore
updates only the counters in those rcu_node structures corresponding
to the boot CPU, up to and including the root rcu_node structure.
The counters for the remaining rcu_node structures are updated by the
rcu_scheduler_starting() function, which executes just before the first
non-boot kthread is spawned.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Because both normal and expedited grace periods increment their respective
counters on their pre-scheduler early boot fastpaths, the rcu_gp_oldstate
structure no longer needs its ->rgos_polled field. This commit therefore
removes this field, shrinking this structure so that it is the same size
as an rcu_head structure.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit causes the early boot single-CPU synchronize_rcu() fastpath to
update the rcu_state and rcu_node structures' ->gp_seq and ->gp_seq_needed
counters. This will allow the full-state polled grace-period APIs to
detect all normal grace periods without the need to track the special
combined polling-only counter, which is a step towards removing the
->rgos_polled field from the rcu_gp_oldstate, thereby reducing its size
by one third.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Now that the grace-period fast path can only happen during the
pre-scheduler portion of early boot, this fast path can no longer block
run-time RCU Tasks and RCU Tasks Trace grace periods. This commit
therefore removes the conditional cond_resched_tasks_rcu_qs() invocation.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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It would be good do reduce the size of the rcu_gp_oldstate structure
from three unsigned long instances to two, but this requires that the
boot-time optimized grace periods update the various ->gp_seq fields.
Updating these fields in the rcu_state structure and in all of the
rcu_node structures is at least semi-reasonable, but updating them in
all of the rcu_data structures is a bridge too far. This means that if
there are too many early boot-time grace periods, the ->gp_seq field in
the rcu_data structure cannot be trusted. This commit therefore sets
each rcu_data structure's ->gpwrap field to provide the necessary impetus
for a suitable level of distrust.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The run-time single-CPU grace-period optimization applies only to
kernels built with CONFIG_SMP=y && CONFIG_PREEMPTION=y that are running
on a single-CPU system. But a kernel intended for a single-CPU system
should instead be built with CONFIG_SMP=n, and in any case, single-CPU
systems running Linux no longer appear to be the common case. Plus this
optimization results in the rcu_gp_oldstate structure being half again
larger than it needs to be.
This commit therefore disables the run-time single-CPU grace-period
optimization, so that this optimization applies only during the
pre-scheduler portion of the boot sequence.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The cond_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.
This commit therefore adds yet another member of the full-state RCU
grace-period polling API, which is the cond_synchronize_rcu_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.
[ paulmck: Apply feedback from kernel test robot and Julia Lawall. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit removes the blank line preceding the oldstate parameter to
the docbook header for the poll_state_synchronize_rcu() function and
marks uses of this parameter later in that header.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
|
|
The start_poll_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.
This commit therefore adds the next member of the full-state RCU
grace-period polling API, namely the start_poll_synchronize_rcu_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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|
The get_state_synchronize_rcu() API compresses the combined expedited and
normal grace-period states into a single unsigned long, which conserves
storage, but can miss grace periods in certain cases involving overlapping
normal and expedited grace periods. Missing the occasional grace period
is usually not a problem, but there are use cases that care about each
and every grace period.
This commit therefore adds the next member of the full-state RCU
grace-period polling API, namely the get_state_synchronize_rcu_full()
function. This uses up to three times the storage (rcu_gp_oldstate
structure instead of unsigned long), but is guaranteed not to miss
grace periods.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The get_completed_synchronize_rcu() and poll_state_synchronize_rcu()
APIs compress the combined expedited and normal grace-period states into a
single unsigned long, which conserves storage, but can miss grace periods
in certain cases involving overlapping normal and expedited grace periods.
Missing the occasional grace period is usually not a problem, but there
are use cases that care about each and every grace period.
This commit therefore adds the first members of the full-state RCU
grace-period polling API, namely the get_completed_synchronize_rcu_full()
and poll_state_synchronize_rcu_full() functions. These use up to three
times the storage (rcu_gp_oldstate structure instead of unsigned long),
but which are guaranteed not to miss grace periods, at least in situations
where the single-CPU grace-period optimization does not apply.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently the monitor work is scheduled with a fixed interval of HZ/20,
which is roughly 50 milliseconds. The drawback of this approach is
low utilization of the 512 page slots in scenarios with infrequence
kvfree_rcu() calls. For example on an Android system:
<snip>
kworker/3:3-507 [003] .... 470.286305: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000d0f0dde5 nr_records=6
kworker/6:1-76 [006] .... 470.416613: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000ea0d6556 nr_records=1
kworker/6:1-76 [006] .... 470.416625: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000003e025849 nr_records=9
kworker/3:3-507 [003] .... 471.390000: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000815a8713 nr_records=48
kworker/1:1-73 [001] .... 471.725785: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000fda9bf20 nr_records=3
kworker/1:1-73 [001] .... 471.725833: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000a425b67b nr_records=76
kworker/0:4-1411 [000] .... 472.085673: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000007996be9d nr_records=1
kworker/0:4-1411 [000] .... 472.085728: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000d0f0dde5 nr_records=5
kworker/6:1-76 [006] .... 472.260340: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x0000000065630ee4 nr_records=102
<snip>
In many cases, out of 512 slots, fewer than 10 were actually used.
In order to improve batching and make utilization more efficient this
commit sets a drain interval to a fixed 5-seconds interval. Floods are
detected when a page fills quickly, and in that case, the reclaim work
is re-scheduled for the next scheduling-clock tick (jiffy).
After this change:
<snip>
kworker/7:1-371 [007] .... 5630.725708: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000005ab0ffb3 nr_records=121
kworker/7:1-371 [007] .... 5630.989702: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x0000000060c84761 nr_records=47
kworker/7:1-371 [007] .... 5630.989714: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000000babf308 nr_records=510
kworker/7:1-371 [007] .... 5631.553790: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000bb7bd0ef nr_records=169
kworker/7:1-371 [007] .... 5631.553808: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x0000000044c78753 nr_records=510
kworker/5:6-9428 [005] .... 5631.746102: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000d98519aa nr_records=123
kworker/4:7-9434 [004] .... 5632.001758: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x00000000526c9d44 nr_records=322
kworker/4:7-9434 [004] .... 5632.002073: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000002c6a8afa nr_records=185
kworker/7:1-371 [007] .... 5632.277515: rcu_invoke_kfree_bulk_callback: rcu_preempt bulk=0x000000007f4a962f nr_records=510
<snip>
Here, all but one of the cases, more than one hundreds slots were used,
representing an order-of-magnitude improvement.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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As per the comments in include/linux/shrinker.h, .count_objects callback
should return the number of freeable items, but if there are no objects
to free, SHRINK_EMPTY should be returned. The only time 0 is returned
should be when we are unable to determine the number of objects, or the
cache should be skipped for another reason.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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The fill_page_cache_func() function allocates couple of pages to store
kvfree_rcu_bulk_data structures. This is a lightweight (GFP_NORETRY)
allocation which can fail under memory pressure. The function will,
however keep retrying even when the previous attempt has failed.
This retrying is in theory correct, but in practice the allocation is
invoked from workqueue context, which means that if the memory reclaim
gets stuck, these retries can hog the worker for quite some time.
Although the workqueues subsystem automatically adjusts concurrency, such
adjustment is not guaranteed to happen until the worker context sleeps.
And the fill_page_cache_func() function's retry loop is not guaranteed
to sleep (see the should_reclaim_retry() function).
And we have seen this function cause workqueue lockups:
kernel: BUG: workqueue lockup - pool cpus=93 node=1 flags=0x1 nice=0 stuck for 32s!
[...]
kernel: pool 74: cpus=37 node=0 flags=0x1 nice=0 hung=32s workers=2 manager: 2146
kernel: pwq 498: cpus=249 node=1 flags=0x1 nice=0 active=4/256 refcnt=5
kernel: in-flight: 1917:fill_page_cache_func
kernel: pending: dbs_work_handler, free_work, kfree_rcu_monitor
Originally, we thought that the root cause of this lockup was several
retries with direct reclaim, but this is not yet confirmed. Furthermore,
we have seen similar lockups without any heavy memory pressure. This
suggests that there are other factors contributing to these lockups.
However, it is not really clear that endless retries are desireable.
So let's make the fill_page_cache_func() function back off after
allocation failure.
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Most of the MM queue. A few things are still pending.
Liam's maple tree rework didn't make it. This has resulted in a few
other minor patch series being held over for next time.
Multi-gen LRU still isn't merged as we were waiting for mapletree to
stabilize. The current plan is to merge MGLRU into -mm soon and to
later reintroduce mapletree, with a view to hopefully getting both
into 6.1-rc1.
Summary:
- The usual batches of cleanups from Baoquan He, Muchun Song, Miaohe
Lin, Yang Shi, Anshuman Khandual and Mike Rapoport
- Some kmemleak fixes from Patrick Wang and Waiman Long
- DAMON updates from SeongJae Park
- memcg debug/visibility work from Roman Gushchin
- vmalloc speedup from Uladzislau Rezki
- more folio conversion work from Matthew Wilcox
- enhancements for coherent device memory mapping from Alex Sierra
- addition of shared pages tracking and CoW support for fsdax, from
Shiyang Ruan
- hugetlb optimizations from Mike Kravetz
- Mel Gorman has contributed some pagealloc changes to improve
latency and realtime behaviour.
- mprotect soft-dirty checking has been improved by Peter Xu
- Many other singleton patches all over the place"
[ XFS merge from hell as per Darrick Wong in
https://lore.kernel.org/all/YshKnxb4VwXycPO8@magnolia/ ]
* tag 'mm-stable-2022-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (282 commits)
tools/testing/selftests/vm/hmm-tests.c: fix build
mm: Kconfig: fix typo
mm: memory-failure: convert to pr_fmt()
mm: use is_zone_movable_page() helper
hugetlbfs: fix inaccurate comment in hugetlbfs_statfs()
hugetlbfs: cleanup some comments in inode.c
hugetlbfs: remove unneeded header file
hugetlbfs: remove unneeded hugetlbfs_ops forward declaration
hugetlbfs: use helper macro SZ_1{K,M}
mm: cleanup is_highmem()
mm/hmm: add a test for cross device private faults
selftests: add soft-dirty into run_vmtests.sh
selftests: soft-dirty: add test for mprotect
mm/mprotect: fix soft-dirty check in can_change_pte_writable()
mm: memcontrol: fix potential oom_lock recursion deadlock
mm/gup.c: fix formatting in check_and_migrate_movable_page()
xfs: fail dax mount if reflink is enabled on a partition
mm/memcontrol.c: remove the redundant updating of stats_flush_threshold
userfaultfd: don't fail on unrecognized features
hugetlb_cgroup: fix wrong hugetlb cgroup numa stat
...
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ctxt.2022.07.05a: Linux-kernel memory model development branch.
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|
'poll.2022.07.21a', 'rcu-tasks.2022.06.21a' and 'torture.2022.06.21a' into HEAD
doc.2022.06.21a: Documentation updates.
fixes.2022.07.19a: Miscellaneous fixes.
nocb.2022.07.19a: Callback-offload updates.
poll.2022.07.21a: Polled grace-period updates.
rcu-tasks.2022.06.21a: Tasks RCU updates.
torture.2022.06.21a: Torture-test updates.
|
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This commit adds expedited grace-period functionality to RCU's polled
grace-period API, adding start_poll_synchronize_rcu_expedited() and
cond_synchronize_rcu_expedited(), which are similar to the existing
start_poll_synchronize_rcu() and cond_synchronize_rcu() functions,
respectively.
Note that although start_poll_synchronize_rcu_expedited() can be invoked
very early, the resulting expedited grace periods are not guaranteed
to start until after workqueues are fully initialized. On the other
hand, both synchronize_rcu() and synchronize_rcu_expedited() can also
be invoked very early, and the resulting grace periods will be taken
into account as they occur.
[ paulmck: Apply feedback from Neeraj Upadhyay. ]
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
|
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Currently, this code could splat:
oldstate = get_state_synchronize_rcu();
synchronize_rcu_expedited();
WARN_ON_ONCE(!poll_state_synchronize_rcu(oldstate));
This situation is counter-intuitive and user-unfriendly. After all, there
really was a perfectly valid full grace period right after the call to
get_state_synchronize_rcu(), so why shouldn't poll_state_synchronize_rcu()
know about it?
This commit therefore makes the polled grace-period API aware of expedited
grace periods in addition to the normal grace periods that it is already
aware of. With this change, the above code is guaranteed not to splat.
Please note that the above code can still splat due to counter wrap on the
one hand and situations involving partially overlapping normal/expedited
grace periods on the other. On 64-bit systems, the second is of course
much more likely than the first. It is possible to modify this approach
to prevent overlapping grace periods from causing splats, but only at
the expense of greatly increasing the probability of counter wrap, as
in within milliseconds on 32-bit systems and within minutes on 64-bit
systems.
This commit is in preparation for polled expedited grace periods.
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit switches the existing polled grace-period APIs to use a
new ->gp_seq_polled counter in the rcu_state structure. An additional
->gp_seq_polled_snap counter in that same structure allows the normal
grace period kthread to interact properly with the !SMP !PREEMPT fastpath
through synchronize_rcu(). The first of the two to note the end of a
given grace period will make knowledge of this transition available to
the polled API.
This commit is in preparation for polled expedited grace periods.
[ paulmck: Fix use of rcu_state.gp_seq_polled to start normal grace period. ]
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Co-developed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit introduces a RCU_NOCB_CPU_CB_BOOST Kconfig option that
prevents rcuo kthreads from running at real-time priority, even in
kernels built with RCU_BOOST. This capability is important to devices
needing low-latency (as in a few milliseconds) response from expedited
RCU grace periods, but which are not running a classic real-time workload.
On such devices, permitting the rcuo kthreads to run at real-time priority
results in unacceptable latencies imposed on the application tasks,
which run as SCHED_OTHER.
See for example the following trace output:
<snip>
<...>-60 [006] d..1 2979.028717: rcu_batch_start: rcu_preempt CBs=34619 bl=270
<snip>
If that rcuop kthread were permitted to run at real-time SCHED_FIFO
priority, it would monopolize its CPU for hundreds of milliseconds
while invoking those 34619 RCU callback functions, which would cause an
unacceptably long latency spike for many application stacks on Android
platforms.
However, some existing real-time workloads require that callback
invocation run at SCHED_FIFO priority, for example, those running on
systems with heavy SCHED_OTHER background loads. (It is the real-time
system's administrator's responsibility to make sure that important
real-time tasks run at a higher priority than do RCU's kthreads.)
Therefore, this new RCU_NOCB_CPU_CB_BOOST Kconfig option defaults to
"y" on kernels built with PREEMPT_RT and defaults to "n" otherwise.
The effect is to preserve current behavior for real-time systems, but for
other systems to allow expedited RCU grace periods to run with real-time
priority while continuing to invoke RCU callbacks as SCHED_OTHER.
As you would expect, this RCU_NOCB_CPU_CB_BOOST Kconfig option has no
effect except on CPUs with offloaded RCU callbacks.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
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Callbacks are invoked in RCU kthreads when calbacks are offloaded
(rcu_nocbs boot parameter) or when RCU's softirq handler has been
offloaded to rcuc kthreads (use_softirq==0). The current code allows
for the rcu_nocbs case but not the use_softirq case. This commit adds
support for the use_softirq case.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
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Add a comment to explain why !rcu_preempt_blocked_readers_cgp() condition
is required on root rnp node, for GP completion check in rcu_gp_fqs_loop().
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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This commit saves a line of code by initializing the rcu_gp_fqs()
function's first_gp_fqs local variable in its declaration.
Reported-by: Frederic Weisbecker <frederic@kernel.org>
Reported-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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monitor_todo is not needed as the work struct already tracks
if work is pending. Just use that to know if work is pending
using schedule_delayed_work() helper.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
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When a CPU is slow to provide a quiescent state for a given grace
period, RCU takes steps to encourage that CPU to get with the
quiescent-state program in a more timely fashion. These steps
include these flags in the rcu_data structure:
1. ->rcu_urgent_qs, which causes the scheduling-clock interrupt to
request an otherwise pointless context switch from the scheduler.
2. ->rcu_need_heavy_qs, which causes both cond_resched() and RCU's
context-switch hook to do an immediate momentary quiscent state.
3. ->rcu_need_heavy_qs, which causes the scheduler-clock tick to
be enabled even on nohz_full CPUs with only one runnable task.
These flags are of course cleared once the corresponding CPU has passed
through a quiescent state. Unless that quiescent state is the CPU
going offline, which means that when the CPU comes back online, it will
needlessly consume additional CPU time and incur additional latency,
which constitutes a minor but very real performance bug.
This commit therefore adds the call to rcu_disable_urgency_upon_qs()
that clears these flags to the CPU-hotplug offlining code path.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
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Currently, the rcu_node structure's ->cbovlmask field is set in call_rcu()
when a given CPU is suffering from callback overload. But if that CPU
goes offline, the outgoing CPU's callbacks is migrated to the running
CPU, which is likely to overload the running CPU. However, that CPU's
bit in its leaf rcu_node structure's ->cbovlmask field remains zero.
Initially, this is OK because the outgoing CPU's bit remains set.
However, that bit will be cleared at the next end of a grace period,
at which time it is quite possible that the running CPU will still
be overloaded. If the running CPU invokes call_rcu(), then overload
will be checked for and the bit will be set. Except that there is no
guarantee that the running CPU will invoke call_rcu(), in which case the
next grace period will fail to take the running CPU's overload condition
into account. Plus, because the bit is not set, the end of the grace
period won't check for overload on this CPU.
This commit therefore adds a call to check_cb_ovld_locked() in
rcutree_migrate_callbacks() to set the running CPU's ->cbovlmask bit
appropriately.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
|
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The force-quiesce-state loop function rcu_gp_fqs_loop() checks for
callback overloading and does an immediate initial scan for idle CPUs
if so. However, subsequent rescans will be carried out at as leisurely a
rate as they always are, as specified by the rcutree.jiffies_till_next_fqs
module parameter. It might be tempting to just continue immediately
rescanning, but this turns the RCU grace-period kthread into a CPU hog.
It might also be tempting to reduce the time between rescans to a single
jiffy, but this can be problematic on larger systems.
This commit therefore divides the normal time between rescans by three,
rounding up. Thus a small system running at HZ=1000 that is suffering
from callback overload will wait only one jiffy instead of the normal
three between rescans.
[ paulmck: Apply Neeraj Upadhyay feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
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Context tracking's state and dynticks counter are going to be merged
in a single field so that both updates can happen atomically and at the
same time. Prepare for that with converting the state into an atomic_t.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
|
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Move the core RCU eqs/dynticks functions to context tracking so that
we can later merge all that code within context tracking.
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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To prepare for migrating the RCU eqs accounting code to context tracking,
split the last-resort deferred nocb resched from rcu_user_enter() and
move it into a separate call from context tracking.
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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The RCU eqs tracking is going to be performed by the context tracking
subsystem. The related nesting counters thus need to be moved to the
context tracking structure.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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The RCU eqs tracking is going to be performed by the context tracking
subsystem. The related nesting counters thus need to be moved to the
context tracking structure.
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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In order to prepare for merging RCU dynticks counter into the context
tracking state, move the rcu_data's dynticks field to the context
tracking structure. It will later be mixed within the context tracking
state itself.
[ paulmck: Move enum ctx_state into global scope. ]
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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Now rcu_irq_enter/exit() is an unnecessary middle call between
ct_irq_enter/exit() and nmi_irq_enter/exit(). Take this opportunity
to remove the former functions and move the comments above them to the
new entrypoints.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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The RCU dynticks counter is going to be merged into the context tracking
subsystem. Start with moving the idle extended quiescent states
entrypoints to context tracking. For now those are dumb redirections to
existing RCU calls.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
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Currently shrinkers are anonymous objects. For debugging purposes they
can be identified by count/scan function names, but it's not always
useful: e.g. for superblock's shrinkers it's nice to have at least an
idea of to which superblock the shrinker belongs.
This commit adds names to shrinkers. register_shrinker() and
prealloc_shrinker() functions are extended to take a format and arguments
to master a name.
In some cases it's not possible to determine a good name at the time when
a shrinker is allocated. For such cases shrinker_debugfs_rename() is
provided.
The expected format is:
<subsystem>-<shrinker_type>[:<instance>]-<id>
For some shrinkers an instance can be encoded as (MAJOR:MINOR) pair.
After this change the shrinker debugfs directory looks like:
$ cd /sys/kernel/debug/shrinker/
$ ls
dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42
mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43
mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44
rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49
sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13
sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36
sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19
sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10
sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9
sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37
sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38
sb-dax-11 sb-proc-45 sb-tmpfs-35
sb-debugfs-7 sb-proc-46 sb-tmpfs-40
[roman.gushchin@linux.dev: fix build warnings]
Link: https://lkml.kernel.org/r/Yr+ZTnLb9lJk6fJO@castle
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lkml.kernel.org/r/20220601032227.4076670-4-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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This commit applies the "noinstr" tag to the rcu_idle_enter() and
rcu_idle_exit() functions, which are invoked from portions of the idle
loop that cannot be instrumented. These tags require reworking the
rcu_eqs_enter() and rcu_eqs_exit() functions that these two functions
invoke in order to cause them to use normal assertions rather than
lockdep. In addition, within rcu_idle_exit(), the raw versions of
local_irq_save() and local_irq_restore() are used, again to avoid issues
with lockdep in uninstrumented code.
This patch is based in part on an earlier patch by Jiri Olsa, discussions
with Peter Zijlstra and Frederic Weisbecker, earlier changes by Thomas
Gleixner, and off-list discussions with Yonghong Song.
Link: https://lore.kernel.org/lkml/20220515203653.4039075-1-jolsa@kernel.org/
Reported-by: Jiri Olsa <jolsa@kernel.org>
Reported-by: Alexei Starovoitov <ast@kernel.org>
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Yonghong Song <yhs@fb.com>
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It is currently up to the caller to handle stale return values from
get_state_synchronize_rcu(). If poll_state_synchronize_rcu() returned
true once, a grace period has elapsed, regardless of the fact that counter
wrap might cause some future poll_state_synchronize_rcu() invocation to
return false. For example, the caller might store a separate flag that
indicates whether some previous call to poll_state_synchronize_rcu()
determined that the relevant grace period had already ended.
This approach works, but it requires extra storage and is easy to get
wrong. This commit therefore introduces a get_completed_synchronize_rcu()
that returns a cookie that causes poll_state_synchronize_rcu() to always
return true. This already-completed cookie can be stored in place of the
cookie that previously caused poll_state_synchronize_rcu() to return true.
It can also be used to flag a given structure as not having been exposed
to readers, and thus not requiring a grace period to elapse.
This commit is in preparation for polled expedited grace periods.
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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Currently, poll_state_synchronize_rcu() uses rcu_seq_done() to check
whether the specified grace period has completed. However, rcu_seq_done()
does a simple comparison that reserves have of the sequence-number space
for uncompleted grace periods. This has the unfortunate side-effect
of not handling sequence-number wrap gracefully. Of course, one can
argue that if someone has already waited for half of the full range of
grace periods, they can wait for the other half, but why wait at all in
this case?
This commit therefore creates a rcu_seq_done_exact() that counts as
uncompleted only the two grace periods during which the sequence number
might have been handed out, while still being uncompleted. This way,
if sequence-number wrap happens to hit that range, at most two additional
grace periods need be waited for.
This commit is in preparation for polled expedited grace periods.
Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/
Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing
Cc: Brian Foster <bfoster@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ian Kent <raven@themaw.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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