On Wed, Oct 15, 2014 at 3:08 PM, Patrick Palka <patr...@parcs.ath.cx> wrote: > On Wed, Oct 15, 2014 at 9:41 AM, Patrick Palka <patr...@parcs.ath.cx> wrote: >> Instead of open-coding the equivalent cmpxchg loop we can just use >> atomic_set_mask and atomic_clear_mask to atomically OR or AND >> the value in &buffer->record_disabled. >> >> Cc: Steven Rostedt <rost...@goodmis.org> >> Cc: Ingo Molnar <mi...@redhat.com> >> Signed-off-by: Patrick Palka <patr...@parcs.ath.cx> >> --- >> >> NB: I have only tested this patch on x86_64 by booting with >> CONFIG_RING_BUFFER_STARTUP_TEST=y. >> >> kernel/trace/ring_buffer.c | 16 ++-------------- >> 1 file changed, 2 insertions(+), 14 deletions(-) >> >> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c >> index 2d75c94..e15ce2a 100644 >> --- a/kernel/trace/ring_buffer.c >> +++ b/kernel/trace/ring_buffer.c >> @@ -3050,13 +3050,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_record_enable); >> */ >> void ring_buffer_record_off(struct ring_buffer *buffer) >> { >> - unsigned int rd; >> - unsigned int new_rd; >> - >> - do { >> - rd = atomic_read(&buffer->record_disabled); >> - new_rd = rd | RB_BUFFER_OFF; >> - } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); >> + atomic_set_mask(RB_BUFFER_OFF, &buffer->record_disabled); >> } >> EXPORT_SYMBOL_GPL(ring_buffer_record_off); >> >> @@ -3073,13 +3067,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_record_off); >> */ >> void ring_buffer_record_on(struct ring_buffer *buffer) >> { >> - unsigned int rd; >> - unsigned int new_rd; >> - >> - do { >> - rd = atomic_read(&buffer->record_disabled); >> - new_rd = rd & ~RB_BUFFER_OFF; >> - } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); >> + atomic_clear_mask(RB_BUFFER_OFF, &buffer->record_disabled); >> } >> EXPORT_SYMBOL_GPL(ring_buffer_record_on); >> >> -- >> 2.1.2.443.g670a3c1 >> > > It just occurred to me that atomic_clear_mask and atomic_set_mask > expect to take an int *, not an atomic_t *, so this patch is bogus... > Sorry for the noise.
Uh, actually, the generic implementations of these functions (defined in include/asm-generic/atomic.h) _do_ take an atomic_t *. It's the specialized x86 definitions of these functions (defined in arch/x86/include/asm/atomic.h) that take (expect) an int *. So this patch is not bogus; the x86 specializations for atomic_clear_mask and atomic_set_mask are. I will try to fix this in a separate patch. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/