From: Lai Jiangshan Date: Wed, 15 Jul 2009 08:27:30 +0000 (+0800) Subject: ring_buffer: Fix warning while ignoring cmpxchg return value X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=da706d8bc833e7153622435560422e653bdb2e94;p=linux-beck.git 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 Acked-by: Steven Rostedt Signed-off-by: Frederic Weisbecker --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index e648ba4f70e0..51633d74a21e 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -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.