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ring-buffer: Update write stamp with the correct ts

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The write stamp, used to calculate deltas between events, was updated with
the stale "ts" value in the "info" structure, and not with the updated "ts"
variable. This caused the deltas between events to be inaccurate, and when
crossing into a new sub buffer, had time go backwards.

Link: https://lkml.kernel.org/r/20201124223917.795844-1-elavila@google.com

Cc: stable@vger.kernel.org
Fixes: a389d86f7f ("ring-buffer: Have nested events still record running time stamp")
Reported-by: "J. Avila" <elavila@google.com>
Tested-by: Daniel Mentz <danielmentz@google.com>
Tested-by: Will McVicker <willmcvicker@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-11-27 11:20:58 -05:00
parent fbc6e1c6e0
commit 55ea4cf403
1 changed files with 1 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
kernel/trace/ring_buffer.c
View file

@ -3291,7 +3291,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
/* Nothing came after this event between C and E */ /* Nothing came after this event between C and E */
info->delta = ts - info->after; info->delta = ts - info->after;
(void)rb_time_cmpxchg(&cpu_buffer->write_stamp, (void)rb_time_cmpxchg(&cpu_buffer->write_stamp,
info->after, info->ts); info->after, ts);
info->ts = ts; info->ts = ts;
} else { } else {
/* /*