linux-kernel - [PATCH] lib/spinlock_debug: avoid one thread can not obtain the spinlock for a long time.

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Date:	Wed, 30 Apr 2014 13:04:31 -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
Subject: [PATCH] lib/spinlock_debug: avoid one thread can not obtain the
 spinlock for a long time.

loops_per_jiffy is larger than expectation that possible
causes one thread can not obtain the spin lock for a long time.
So use cpu_clock() to reach timeout in one second which can
avoid HARD LOCKUP.

Signed-off-by: Chuansheng Liu <chuansheng.liu@...el.com>
Signed-off-by: xiaoming wang <xiaoming.wang@...el.com>
---
 kernel/locking/spinlock_debug.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 0374a59..5d3c4f3 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -105,13 +105,19 @@ static inline void debug_spin_unlock(raw_spinlock_t *lock)
 
 static void __spin_lock_debug(raw_spinlock_t *lock)
 {
-	u64 i;
+	u64 i, t;
 	u64 loops = loops_per_jiffy * HZ;
+	u64 one_second = 1000000000;
+	u32 this_cpu = raw_smp_processor_id();
+
+	t = cpu_clock(this_cpu);
 
 	for (i = 0; i < loops; i++) {
 		if (arch_spin_trylock(&lock->raw_lock))
 			return;
 		__delay(1);
+		if (cpu_clock(this_cpu) - t > one_second)
+			break;
 	}
 	/* lockup suspected: */
 	spin_dump(lock, "lockup suspected");
-- 
1.7.1


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