tracing: fix deadlock when setting set_ftrace_pid
Impact: fix deadlock while using set_ftrace_pid
Reproducer:
# cd /sys/kernel/debug/tracing
# echo $$ > set_ftrace_pid
then, console becomes hung.
Details:
when writing set_ftracepid, kernel callstack is following
ftrace_pid_write()
mutex_lock(&ftrace_lock);
ftrace_update_pid_func()
mutex_lock(&ftrace_lock);
mutex_unlock(&ftrace_lock);
mutex_unlock(&ftrace_lock);
then, system always deadlocks when ftrace_pid_write() is called.
In past days, ftrace_pid_write() used ftrace_start_lock, but
commit e6ea44e9b4
consolidated
ftrace_start_lock to ftrace_lock.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <20090306151155.0778.A69D9226@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
parent
422d3c7a57
commit
10dd3ebe21
1 changed files with 1 additions and 6 deletions
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@ -218,10 +218,8 @@ static void ftrace_update_pid_func(void)
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{
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{
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ftrace_func_t func;
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ftrace_func_t func;
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mutex_lock(&ftrace_lock);
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if (ftrace_trace_function == ftrace_stub)
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if (ftrace_trace_function == ftrace_stub)
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goto out;
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return;
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func = ftrace_trace_function;
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func = ftrace_trace_function;
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@ -238,9 +236,6 @@ static void ftrace_update_pid_func(void)
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#else
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#else
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__ftrace_trace_function = func;
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__ftrace_trace_function = func;
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#endif
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#endif
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out:
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mutex_unlock(&ftrace_lock);
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}
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}
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/* set when tracing only a pid */
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/* set when tracing only a pid */
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