Messages in this thread | | | Subject | Re: [BUG] WARNING: at kernel/trace/ring_buffer.c:3420 | From | Steven Rostedt <> | Date | Mon, 08 Mar 2010 10:03:16 -0500 |
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On Mon, 2010-03-08 at 14:50 +0800, Lai Jiangshan wrote: > Li Zefan wrote: > > While running a ftrace test, a kernel warning showed up. The bug is not so > > easy to reproduce, normally it takes 30 mins to 2 hours. > > > > After revering 3c05d7482777f15e71bb4cb1ba78dee2800dfec6, I ran the test > > for 15 hours, and the bug seems disapeared. > > > > This bug exhausted us, we found a issue: a tiny window which is > one of causes of this bug. This patch is to close this tiny window. > (bug is not fixed) > > From: Lai Jiangshan <laijs@cn.fujitsu.com> > > ringbuffer resizing and reseting will increase the ->record_disabled > and then wait until a rcu_shced grace period passes. > > Contrarily, testing ->record_disabled should be at the same > preempt disabled critical region as writing into ringbuffer, otherwise > it will leave a window break ringbuffer resizing or reseting.
So the resizing and the resetting need a synchronize_sched() after the disabling of the buffers, right?
-- Steve
> > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > Reported-by: Li Zefan <lizf@cn.fujitsu.com> > --- > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 8c1b2d2..54191d6 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -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)) > >
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