When calling rb_buffer_peek() from ring_buffer_consume() and a
padding event is returned, the function rb_advance_reader() is
called twice. This may lead to missing samples or under high
workloads to the warning below. This patch fixes this. If a padding
event is returned by rb_buffer_peek() it will be consumed by the
calling function now.
Also, I simplified some code in ring_buffer_consume().
------------[ cut here ]------------
WARNING: at /dev/shm/.source/linux/kernel/trace/ring_buffer.c:2289 rb_advance_reader+0x2e/0xc5()
Hardware name: Anaheim
Modules linked in:
Pid: 29, comm: events/2 Tainted: G W 2.6.31-rc3-oprofile-x86_64
-standard-00059-g5050dc2 #1
Call Trace:
[<
ffffffff8106776f>] ? rb_advance_reader+0x2e/0xc5
[<
ffffffff81039ffe>] warn_slowpath_common+0x77/0x8f
[<
ffffffff8103a025>] warn_slowpath_null+0xf/0x11
[<
ffffffff8106776f>] rb_advance_reader+0x2e/0xc5
[<
ffffffff81068bda>] ring_buffer_consume+0xa0/0xd2
[<
ffffffff81326933>] op_cpu_buffer_read_entry+0x21/0x9e
[<
ffffffff810be3af>] ? __find_get_block+0x4b/0x165
[<
ffffffff8132749b>] sync_buffer+0xa5/0x401
[<
ffffffff810be3af>] ? __find_get_block+0x4b/0x165
[<
ffffffff81326c1b>] ? wq_sync_buffer+0x0/0x78
[<
ffffffff81326c76>] wq_sync_buffer+0x5b/0x78
[<
ffffffff8104aa30>] worker_thread+0x113/0x1ac
[<
ffffffff8104dd95>] ? autoremove_wake_function+0x0/0x38
[<
ffffffff8104a91d>] ? worker_thread+0x0/0x1ac
[<
ffffffff8104dc9a>] kthread+0x88/0x92
[<
ffffffff8100bdba>] child_rip+0xa/0x20
[<
ffffffff8104dc12>] ? kthread+0x0/0x92
[<
ffffffff8100bdb0>] ? child_rip+0x0/0x20
---[ end trace
f561c0a58fcc89bd ]---
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <stable@kernel.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* the box. Return the padding, and we will release
* the current locks, and try again.
*/
- rb_advance_reader(cpu_buffer);
return event;
case RINGBUF_TYPE_TIME_EXTEND:
if (dolock)
spin_lock(&cpu_buffer->reader_lock);
event = rb_buffer_peek(buffer, cpu, ts);
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ rb_advance_reader(cpu_buffer);
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);
spin_lock(&cpu_buffer->reader_lock);
event = rb_buffer_peek(buffer, cpu, ts);
- if (!event)
- goto out_unlock;
-
- rb_advance_reader(cpu_buffer);
+ if (event)
+ rb_advance_reader(cpu_buffer);
- out_unlock:
if (dolock)
spin_unlock(&cpu_buffer->reader_lock);
local_irq_restore(flags);