Merge tag 'trace-fixes-v3.17-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
03900197 · Linus Torvalds <[email protected]> · 2014-10-03 13:31:57 -07:00
Pull trace ring buffer iterator fix from Steven Rostedt:
"While testing some new changes for 3.18, I kept hitting a bug every so
often in the ring buffer. At first I thought it had to do with some
of the changes I was working on, but then testing something else I
realized that the bug was in 3.17 itself. I ran several bisects as
the bug was not very reproducible, and finally came up with the commit
that I could reproduce easily within a few minutes, and without the
change I could run the tests over an hour without issue. The change
fit the bug and I figured out a fix. That bad commit was:
Commit 651e22f2701b "ring-buffer: Always reset iterator to reader page"
This commit fixed a bug, but in the process created another one. It
used the wrong value as the cached value that is used to see if things
changed while an iterator was in use. This made it look like a change
always happened, and could cause the iterator to go into an infinite
loop"
* tag 'trace-fixes-v3.17-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ring-buffer: Fix infinite spin in reading buffer
- Commit
- 039001972a959ab31008a3924ff9519063371bc2
- Parents
- 7d1419f3 · 24607f11
Merge commit. Changes below are compared with the first parent: 7d1419f3.
Changes
1 files changed · +1 −1
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b38fb2b..2d75c94 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3359,7 +3359,7 @@ static void rb_iter_reset(struct ring_buffer_iter *iter)
iter->head = cpu_buffer->reader_page->read;
iter->cache_reader_page = iter->head_page;
- iter->cache_read = iter->head;
+ iter->cache_read = cpu_buffer->read;
if (iter->head)
iter->read_stamp = cpu_buffer->read_stamp;