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ring-buffer: Move disabled check into preempt disable section

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commit 52fbe9cde7 upstream.

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.

Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4B949E43.2010906@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Lai Jiangshan 2010-03-08 14:50:43 +08:00 committed by Greg Kroah-Hartman
parent a0d8ffd630
commit 9dfa691cae
1 changed files with 6 additions and 6 deletions
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12
kernel/trace/ring_buffer.c
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@ -2237,12 +2237,12 @@ 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;
@ -2474,11 +2474,11 @@ 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))