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Commit f7112949 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
Browse files

ring-buffer: Synchronize resizing buffer with reader lock 



We got a sudden panic when we reduced the size of the
ringbuffer.

We can reproduce the panic by the following steps:

echo 1 > events/sched/enable
cat trace_pipe > /dev/null &

while ((1))
do
echo 12000 > buffer_size_kb
echo 512 > buffer_size_kb
done

(not more than 5 seconds, panic ...)

Reported-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4AF01735.9060409@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 6d3f1e12

kernel/trace/ring_buffer.c

+2 −0
Original line number Diff line number Diff line
@@ -1193,6 +1193,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) 
	atomic_inc(&cpu_buffer->record_disabled);

	synchronize_sched();



	spin_lock_irq(&cpu_buffer->reader_lock);

	rb_head_page_deactivate(cpu_buffer);



	for (i = 0; i < nr_pages; i++) {
@@ -1207,6 +1208,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) 
		return;



	rb_reset_cpu(cpu_buffer);

	spin_unlock_irq(&cpu_buffer->reader_lock);



	rb_check_pages(cpu_buffer);