[PATCH 3/3] kcov: remove useless barrier()s

Andrey Ryabinin
2017-09-19T12:44:44Z

As comment says barriers needed for preempt_schedule_irq() case
where in_interrupt() returns false. But we don't use in_interrupt()
since b274c0bb394c ("kcov: properly check if we are in an interrupt").

Now we use in_task() which handles preempt_schedule_irq() case properly,
thus no barrier required.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
kernel/kcov.c | 10 ----------
1 file changed, 10 deletions(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 14cc8c1a7cad..b7fbcbef88c1 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -71,14 +71,6 @@ void notrace __sanitizer_cov_trace_pc(void)

ip -= kaslr_offset();

- /*
- * There is some code that runs in interrupts but for which
- * in_interrupt() returns false (e.g. preempt_schedule_irq()).
- * READ_ONCE()/barrier() effectively provides load-acquire wrt
- * interrupts, there are paired barrier()/WRITE_ONCE() in
- * kcov_ioctl_locked().
- */
- barrier();
area = t->kcov_area;
/* The first word is number of subsequent PCs. */
pos = READ_ONCE(area[0]) + 1;
@@ -228,8 +220,6 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
/* Cache in task struct for performance. */
t->kcov_size = kcov->size;
t->kcov_area = kcov->area;
- /* See comment in __sanitizer_cov_trace_pc(). */
- barrier();
WRITE_ONCE(t->kcov_mode, kcov->mode);
t->kcov = kcov;
kcov->t = t;
--
2.13.5