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Commit 1dbd1951 authored by Li Zefan's avatar Li Zefan Committed by Steven Rostedt
Browse files

tracing: Fix preempt count leak 



While running my ftrace stress test, this showed up:

BUG: sleeping function called from invalid context at mm/mmap.c:233
...
note: cat[3293] exited with preempt_count 1

The bug was introduced by commit 91e86e56
("tracing: Fix recursive user stack trace")

Cc: <stable@kernel.org>
Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4D0089AC.1020802@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent bd1c8b22

kernel/trace/trace.c

+2 −4
Original line number Original line Diff line number Diff line
@@ -1313,12 +1313,10 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) 




	__this_cpu_inc(user_stack_count);

	__this_cpu_inc(user_stack_count);









	event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,

	event = trace_buffer_lock_reserve(buffer, TRACE_USER_STACK,

					  sizeof(*entry), flags, pc);

					  sizeof(*entry), flags, pc);

	if (!event)

	if (!event)

		return;

		goto out_drop_count;

	entry	= ring_buffer_event_data(event);

	entry	= ring_buffer_event_data(event);





	entry->tgid		= current->tgid;

	entry->tgid		= current->tgid;
@@ -1333,8 +1331,8 @@ ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) 
	if (!filter_check_discard(call, entry, buffer, event))

	if (!filter_check_discard(call, entry, buffer, event))

		ring_buffer_unlock_commit(buffer, event);

		ring_buffer_unlock_commit(buffer, event);





 out_drop_count:

	__this_cpu_dec(user_stack_count);

	__this_cpu_dec(user_stack_count);



 out:

 out:

	preempt_enable();

	preempt_enable();

}

}