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ring_buffer: Fix warning while ignoring cmpxchg return value 

kernel/trace/ring_buffer.c: In function 'rb_tail_page_update':
kernel/trace/ring_buffer.c:849: warning: value computed is not used
kernel/trace/ring_buffer.c:850: warning: value computed is not used

Add "(void)"s to fix this warning, because we don't need here to handle
the fail case of cmpxchg, it's fine if an interrupt already did the
job.

Changed from V1:
  Add a comment(which is written by Steven) for it.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
hifive-unleashed-5.1
Lai Jiangshan 2009-07-15 16:27:30 +08:00 committed by Frederic Weisbecker
parent e202687927
commit da706d8bc8
1 changed files with 7 additions and 2 deletions
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9
kernel/trace/ring_buffer.c
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@ -845,9 +845,14 @@ static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
* This will only succeed if an interrupt did
* not come in and change it. In which case, we
* do not want to modify it.
*
* We add (void) to let the compiler know that we do not care
* about the return value of these functions. We use the
* cmpxchg to only update if an interrupt did not already
* do it for us. If the cmpxchg fails, we don't care.
*/
local_cmpxchg(&next_page->write, old_write, val);
local_cmpxchg(&next_page->entries, old_entries, eval);
(void)local_cmpxchg(&next_page->write, old_write, val);
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
/*
* No need to worry about races with clearing out the commit.