diff options
| author | Andrea Righi <andrea.righi@canonical.com> | 2020-11-28 12:15:17 +0300 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-11-30 23:22:05 +0300 |
| commit | 8785f51a17083eee7c37606079c6447afc6ba102 (patch) | |
| tree | 27ebc928988e9b52f7311697260affe50052ea93 | |
| parent | 55ea4cf403800af2ce6b125bc3d853117e0c0456 (diff) | |
| download | linux-8785f51a17083eee7c37606079c6447afc6ba102.tar.xz | |
ring-buffer: Set the right timestamp in the slow path of __rb_reserve_next()
In the slow path of __rb_reserve_next() a nested event(s) can happen
between evaluating the timestamp delta of the current event and updating
write_stamp via local_cmpxchg(); in this case the delta is not valid
anymore and it should be set to 0 (same timestamp as the interrupting
event), since the event that we are currently processing is not the last
event in the buffer.
Link: https://lkml.kernel.org/r/X8IVJcp1gRE+FJCJ@xps-13-7390
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lwn.net/Articles/831207
Fixes: a389d86f7fd0 ("ring-buffer: Have nested events still record running time stamp")
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/ring_buffer.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index bccaf88d3706..35d91b20d47a 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3287,11 +3287,11 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, ts = rb_time_stamp(cpu_buffer->buffer); barrier(); /*E*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) && - info->after < ts) { + info->after < ts && + rb_time_cmpxchg(&cpu_buffer->write_stamp, + info->after, ts)) { /* Nothing came after this event between C and E */ info->delta = ts - info->after; - (void)rb_time_cmpxchg(&cpu_buffer->write_stamp, - info->after, ts); info->ts = ts; } else { /* |