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

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
...@@ -1193,6 +1193,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) ...@@ -1193,6 +1193,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
atomic_inc(&cpu_buffer->record_disabled); atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched(); synchronize_sched();
spin_lock_irq(&cpu_buffer->reader_lock);
rb_head_page_deactivate(cpu_buffer); rb_head_page_deactivate(cpu_buffer);
for (i = 0; i < nr_pages; i++) { for (i = 0; i < nr_pages; i++) {
...@@ -1207,6 +1208,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) ...@@ -1207,6 +1208,7 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
return; return;
rb_reset_cpu(cpu_buffer); rb_reset_cpu(cpu_buffer);
spin_unlock_irq(&cpu_buffer->reader_lock);
rb_check_pages(cpu_buffer); rb_check_pages(cpu_buffer);
......
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