| Date | Tue, 30 Mar 2010 15:54:54 -0700 | From | Greg KH <> | Subject | [016/116] ring-buffer: Move disabled check into preempt disable section |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Lai Jiangshan <laijs@cn.fujitsu.com>
commit 52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4 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>
--- kernel/trace/ring_buffer.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
--- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2237,12 +2237,12 @@ ring_buffer_lock_reserve(struct ring_buf 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 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))
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