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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>
hifive-unleashed-5.1
Steven Rostedt 2010-03-12 19:48:41 -05:00 committed by Steven Rostedt
parent ea14eb7140
commit 283740c619
1 changed files with 4 additions and 4 deletions
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8
kernel/trace/trace.c
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@ -840,10 +840,10 @@ out:
mutex_unlock(&trace_types_lock);
}
static void __tracing_reset(struct trace_array *tr, int cpu)
static void __tracing_reset(struct ring_buffer *buffer, int cpu)
{
ftrace_disable_cpu();
ring_buffer_reset_cpu(tr->buffer, cpu);
ring_buffer_reset_cpu(buffer, cpu);
ftrace_enable_cpu();
}
@ -855,7 +855,7 @@ void tracing_reset(struct trace_array *tr, int cpu)
/* Make sure all commits have finished */
synchronize_sched();
__tracing_reset(tr, cpu);
__tracing_reset(buffer, cpu);
ring_buffer_record_enable(buffer);
}
@ -873,7 +873,7 @@ void tracing_reset_online_cpus(struct trace_array *tr)
tr->time_start = ftrace_now(tr->cpu);
for_each_online_cpu(cpu)
__tracing_reset(tr, cpu);
__tracing_reset(buffer, cpu);
ring_buffer_record_enable(buffer);
}