tree 3bdce475017ff9a5fe82c6d214d27b27e555320c
parent ea14eb714041d40fcc5180b5a586034503650149
author Steven Rostedt <srostedt@redhat.com> 1268441321 -0500
committer Steven Rostedt <rostedt@goodmis.org> 1268443760 -0500

tracing: Use same local variable when resetting the ring buffer

In the ftrace code that resets the ring buffer it references the
buffer with a local variable, but then uses the tr->buffer as the
parameter to reset. If the wakeup tracer is running, which can
switch the tr->buffer with the max saved buffer, this can break
the requirement of disabling the buffer before the reset.

   buffer = tr->buffer;
   ring_buffer_record_disable(buffer);
   synchronize_sched();
   __tracing_reset(tr->buffer, cpu);

If the tr->buffer is swapped, then the reset is not happening to the
buffer that was disabled. This will cause the ring buffer to fail.

Found with Li Zefan's ftrace_stress_test.

Cc: stable@kernel.org
Reported-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>