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Commit 52fbe9cd authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
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ring-buffer: Move disabled check into preempt disable section 



The ring buffer resizing and resetting relies on a schedule RCU
action. The buffers are disabled, a synchronize_sched() is called
and then the resize or reset takes place.

But this only works if the disabling of the buffers are within the
preempt disabled section, otherwise a window exists that the buffers
can be written to while a reset or resize takes place.

Cc: stable@kernel.org
Reported-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B949E43.2010906@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 915a0b57

kernel/trace/ring_buffer.c

+6 −6
Original line number Diff line number Diff line
@@ -2232,12 +2232,12 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) 
	if (ring_buffer_flags != RB_BUFFERS_ON)

		return NULL;



	if (atomic_read(&buffer->record_disabled))

		return NULL;



	/* If we are tracing schedule, we don't want to recurse */

	resched = ftrace_preempt_disable();



	if (atomic_read(&buffer->record_disabled))

		goto out_nocheck;



	if (trace_recursive_lock())

		goto out_nocheck;
@@ -2469,11 +2469,11 @@ int ring_buffer_write(struct ring_buffer *buffer, 
	if (ring_buffer_flags != RB_BUFFERS_ON)

		return -EBUSY;



	if (atomic_read(&buffer->record_disabled))

		return -EBUSY;



	resched = ftrace_preempt_disable();



	if (atomic_read(&buffer->record_disabled))

		goto out;



	cpu = raw_smp_processor_id();



	if (!cpumask_test_cpu(cpu, buffer->cpumask))