ring_buffer: Fix warning while ignoring cmpxchg return value

[safe/jmp/linux-2.6] / kernel / trace / ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index e648ba4..51633d7 100644 (file)
--- 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.