[PATCH] arm: spin one more cycle in timer-based delays
Mason
slash.tmp at free.fr
Tue Nov 15 05:36:33 PST 2016
When polling a tick counter in a busy loop, one might sample the
counter just *before* it is updated, and then again just *after*
it is updated. In that case, while mathematically v2-v1 equals 1,
only epsilon has really passed.
So, if a caller requests an N-cycle delay, we spin until v2-v1
is strictly greater than N to avoid these random corner cases.
Signed-off-by: Mason <slash.tmp at free.fr>
---
arch/arm/lib/delay.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
index 69aad80a3af4..3f1cd15ca102 100644
--- a/arch/arm/lib/delay.c
+++ b/arch/arm/lib/delay.c
@@ -60,7 +60,7 @@ static void __timer_delay(unsigned long cycles)
{
cycles_t start = get_cycles();
- while ((get_cycles() - start) < cycles)
+ while ((get_cycles() - start) <= cycles)
cpu_relax();
}
--
2.9.0
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