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authorZheng Yejian2023-07-26 17:58:04 +0800
committerGreg Kroah-Hartman2023-08-03 10:24:07 +0200
commita3a3c7bddab9b6c5690b20796ef5e332b8c48afb (patch)
tree0475baf6c902617038498527bf814e3e0bc5d169 /kernel/trace/trace_events.c
parent77996fa5c64f7a6733006547ff40a6e02112d43b (diff)
tracing: Fix warning in trace_buffered_event_disable()
[ Upstream commit dea499781a1150d285c62b26659f62fb00824fce ] Warning happened in trace_buffered_event_disable() at WARN_ON_ONCE(!trace_buffered_event_ref) Call Trace: ? __warn+0xa5/0x1b0 ? trace_buffered_event_disable+0x189/0x1b0 __ftrace_event_enable_disable+0x19e/0x3e0 free_probe_data+0x3b/0xa0 unregister_ftrace_function_probe_func+0x6b8/0x800 event_enable_func+0x2f0/0x3d0 ftrace_process_regex.isra.0+0x12d/0x1b0 ftrace_filter_write+0xe6/0x140 vfs_write+0x1c9/0x6f0 [...] The cause of the warning is in __ftrace_event_enable_disable(), trace_buffered_event_enable() was called once while trace_buffered_event_disable() was called twice. Reproduction script show as below, for analysis, see the comments: ``` #!/bin/bash cd /sys/kernel/tracing/ # 1. Register a 'disable_event' command, then: # 1) SOFT_DISABLED_BIT was set; # 2) trace_buffered_event_enable() was called first time; echo 'cmdline_proc_show:disable_event:initcall:initcall_finish' > \ set_ftrace_filter # 2. Enable the event registered, then: # 1) SOFT_DISABLED_BIT was cleared; # 2) trace_buffered_event_disable() was called first time; echo 1 > events/initcall/initcall_finish/enable # 3. Try to call into cmdline_proc_show(), then SOFT_DISABLED_BIT was # set again!!! cat /proc/cmdline # 4. Unregister the 'disable_event' command, then: # 1) SOFT_DISABLED_BIT was cleared again; # 2) trace_buffered_event_disable() was called second time!!! echo '!cmdline_proc_show:disable_event:initcall:initcall_finish' > \ set_ftrace_filter ``` To fix it, IIUC, we can change to call trace_buffered_event_enable() at fist time soft-mode enabled, and call trace_buffered_event_disable() at last time soft-mode disabled. Link: https://lore.kernel.org/linux-trace-kernel/20230726095804.920457-1-zhengyejian1@huawei.com Cc: <mhiramat@kernel.org> Fixes: 0fc1b09ff1ff ("tracing: Use temp buffer when filtering events") Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/trace/trace_events.c')
-rw-r--r--kernel/trace/trace_events.c14
1 files changed, 4 insertions, 10 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index e67923986496..0447c46ef4d7 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -609,7 +609,6 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
{
struct trace_event_call *call = file->event_call;
struct trace_array *tr = file->tr;
- unsigned long file_flags = file->flags;
int ret = 0;
int disable;
@@ -633,6 +632,8 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
break;
disable = file->flags & EVENT_FILE_FL_SOFT_DISABLED;
clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
+ /* Disable use of trace_buffered_event */
+ trace_buffered_event_disable();
} else
disable = !(file->flags & EVENT_FILE_FL_SOFT_MODE);
@@ -671,6 +672,8 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
if (atomic_inc_return(&file->sm_ref) > 1)
break;
set_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
+ /* Enable use of trace_buffered_event */
+ trace_buffered_event_enable();
}
if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
@@ -710,15 +713,6 @@ static int __ftrace_event_enable_disable(struct trace_event_file *file,
break;
}
- /* Enable or disable use of trace_buffered_event */
- if ((file_flags & EVENT_FILE_FL_SOFT_DISABLED) !=
- (file->flags & EVENT_FILE_FL_SOFT_DISABLED)) {
- if (file->flags & EVENT_FILE_FL_SOFT_DISABLED)
- trace_buffered_event_enable();
- else
- trace_buffered_event_disable();
- }
-
return ret;
}