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>
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@ -840,10 +840,10 @@ out:
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mutex_unlock(&trace_types_lock);
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}
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static void __tracing_reset(struct trace_array *tr, int cpu)
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static void __tracing_reset(struct ring_buffer *buffer, int cpu)
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{
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ftrace_disable_cpu();
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ring_buffer_reset_cpu(tr->buffer, cpu);
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ring_buffer_reset_cpu(buffer, cpu);
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ftrace_enable_cpu();
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}
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@ -855,7 +855,7 @@ void tracing_reset(struct trace_array *tr, int cpu)
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/* Make sure all commits have finished */
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synchronize_sched();
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__tracing_reset(tr, cpu);
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__tracing_reset(buffer, cpu);
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ring_buffer_record_enable(buffer);
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}
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@ -873,7 +873,7 @@ void tracing_reset_online_cpus(struct trace_array *tr)
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tr->time_start = ftrace_now(tr->cpu);
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for_each_online_cpu(cpu)
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__tracing_reset(tr, cpu);
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__tracing_reset(buffer, cpu);
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ring_buffer_record_enable(buffer);
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}
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