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author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-04-20 12:30:10 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-04-20 12:30:10 -0700 |
commit | 160062e19001b224370cddeaf652f258fd916fb0 (patch) | |
tree | de1e9fc6f241141a9a5960b170b774841152e2b1 /kernel/trace/ring_buffer.c | |
parent | 7f425895926af100cfdaebd504703325e5c08d3c (diff) | |
parent | 78f7a45dac2a2d2002f98a3a95f7979867868d73 (diff) | |
download | linux-160062e19001b224370cddeaf652f258fd916fb0.tar.bz2 |
Merge tag 'trace-v4.11-rc5-5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull two more ftrace fixes from Steven Rostedt:
"While continuing my development, I uncovered two more small bugs.
One is a race condition when enabling the snapshot function probe
trigger. It enables the probe before allocating the snapshot, and if
the probe triggers first, it stops tracing with a warning that the
snapshot buffer was not allocated.
The seconds is that the snapshot file should show how to use it when
it is empty. But a bug fix from long ago broke the "is empty" test and
the snapshot file no longer displays the help message"
* tag 'trace-v4.11-rc5-5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ring-buffer: Have ring_buffer_iter_empty() return true when empty
tracing: Allocate the snapshot buffer before enabling probe
Diffstat (limited to 'kernel/trace/ring_buffer.c')
-rw-r--r-- | kernel/trace/ring_buffer.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 54e7a90db848..ca47a4fa2986 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3405,11 +3405,23 @@ EXPORT_SYMBOL_GPL(ring_buffer_iter_reset); int ring_buffer_iter_empty(struct ring_buffer_iter *iter) { struct ring_buffer_per_cpu *cpu_buffer; + struct buffer_page *reader; + struct buffer_page *head_page; + struct buffer_page *commit_page; + unsigned commit; cpu_buffer = iter->cpu_buffer; - return iter->head_page == cpu_buffer->commit_page && - iter->head == rb_commit_index(cpu_buffer); + /* Remember, trace recording is off when iterator is in use */ + reader = cpu_buffer->reader_page; + head_page = cpu_buffer->head_page; + commit_page = cpu_buffer->commit_page; + commit = rb_page_commit(commit_page); + + return ((iter->head_page == commit_page && iter->head == commit) || + (iter->head_page == reader && commit_page == head_page && + head_page->read == commit && + iter->head == rb_page_commit(cpu_buffer->reader_page))); } EXPORT_SYMBOL_GPL(ring_buffer_iter_empty); |