linux-kernel - [PATCH] lib/spinlock_debug: Tweak the loop time to fit different

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Date:	Wed, 30 Apr 2014 18:40:38 -0400
From:	"Wang, Xiaoming" <xiaoming.wang@...el.com>
To:	peterz@...radead.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org
Cc:	chuansheng.liu@...el.com, xiaoming.wang@...el.com
Subject: [PATCH] lib/spinlock_debug: Tweak the loop time to fit different
 _delay()

loops_per_jiffy*Hz  is not always 1 second exactly
it depends on the realization of _delay() .
delay_tsc is used as _delay() in arch/x86/lib/delay.c
It makes loop loops_per_jiffy larger than exception
and causes one thread can not obtain the spin lock for
a long time which may trigger HARD LOCKUP in this case.
So we use cpu_clock() which is more accurate.

Signed-off-by: Chuansheng Liu <chuansheng.liu@...el.com>
Signed-off-by: xiaoming wang <xiaoming.wang@...el.com>
---
 kernel/locking/spinlock_debug.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 0374a59..471d26c 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -105,10 +105,13 @@ static inline void debug_spin_unlock(raw_spinlock_t *lock)
 
 static void __spin_lock_debug(raw_spinlock_t *lock)
 {
-	u64 i;
-	u64 loops = loops_per_jiffy * HZ;
+	u64 t;
+	u64 one_second = 1000000000;
+	u32 this_cpu = raw_smp_processor_id();
+
+	t = cpu_clock(this_cpu);
 
-	for (i = 0; i < loops; i++) {
+	while (cpu_clock(this_cpu) - t < one_second) {
 		if (arch_spin_trylock(&lock->raw_lock))
 			return;
 		__delay(1);
-- 
1.7.1

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