diff options
author | Robert Richter <robert.richter@amd.com> | 2009-07-30 13:19:18 -0400 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-08-06 08:20:25 -0400 |
commit | 469535a598f28c13a2a42037e1b778f671af1d16 (patch) | |
tree | 907a3434e87bdab3f37f3c965a230af7af9bdb30 /kernel | |
parent | 3f6e968ef4e1d8d93d8a8505461b0e50a9e97ad8 (diff) |
ring-buffer: Fix advance of reader in rb_buffer_peek()
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>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/trace/ring_buffer.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 2606cee433d..d4d3580a894 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c | |||
@@ -2383,7 +2383,6 @@ rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) | |||
2383 | * the box. Return the padding, and we will release | 2383 | * the box. Return the padding, and we will release |
2384 | * the current locks, and try again. | 2384 | * the current locks, and try again. |
2385 | */ | 2385 | */ |
2386 | rb_advance_reader(cpu_buffer); | ||
2387 | return event; | 2386 | return event; |
2388 | 2387 | ||
2389 | case RINGBUF_TYPE_TIME_EXTEND: | 2388 | case RINGBUF_TYPE_TIME_EXTEND: |
@@ -2519,6 +2518,8 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) | |||
2519 | if (dolock) | 2518 | if (dolock) |
2520 | spin_lock(&cpu_buffer->reader_lock); | 2519 | spin_lock(&cpu_buffer->reader_lock); |
2521 | event = rb_buffer_peek(buffer, cpu, ts); | 2520 | event = rb_buffer_peek(buffer, cpu, ts); |
2521 | if (event && event->type_len == RINGBUF_TYPE_PADDING) | ||
2522 | rb_advance_reader(cpu_buffer); | ||
2522 | if (dolock) | 2523 | if (dolock) |
2523 | spin_unlock(&cpu_buffer->reader_lock); | 2524 | spin_unlock(&cpu_buffer->reader_lock); |
2524 | local_irq_restore(flags); | 2525 | local_irq_restore(flags); |
@@ -2590,12 +2591,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts) | |||
2590 | spin_lock(&cpu_buffer->reader_lock); | 2591 | spin_lock(&cpu_buffer->reader_lock); |
2591 | 2592 | ||
2592 | event = rb_buffer_peek(buffer, cpu, ts); | 2593 | event = rb_buffer_peek(buffer, cpu, ts); |
2593 | if (!event) | 2594 | if (event) |
2594 | goto out_unlock; | 2595 | rb_advance_reader(cpu_buffer); |
2595 | |||
2596 | rb_advance_reader(cpu_buffer); | ||
2597 | 2596 | ||
2598 | out_unlock: | ||
2599 | if (dolock) | 2597 | if (dolock) |
2600 | spin_unlock(&cpu_buffer->reader_lock); | 2598 | spin_unlock(&cpu_buffer->reader_lock); |
2601 | local_irq_restore(flags); | 2599 | local_irq_restore(flags); |