[PARISC] Fix our spinlock implementation
We actually have two separate bad bugs
1. The read_lock implementation spins with disabled interrupts. This is
completely wrong
2. Our spin_lock_irqsave should check to see if interrupts were enabled
before the call and re-enable interrupts around the inner spin loop.
The problem is that if we spin with interrupts off, we can't receive
IPIs. This has resulted in a bug where SMP machines suddenly spit
smp_call_function timeout messages and hang.
The scenario I've caught is
CPU0 does a flush_tlb_all holding the vmlist_lock for write.
CPU1 tries a cat of /proc/meminfo which tries to acquire vmlist_lock for
read
CPU1 is now spinning with interrupts disabled
CPU0 tries to execute a smp_call_function to flush the local tlb caches
This is now a deadlock because CPU1 is spinning with interrupts disabled
and can never receive the IPI
Signed-off-by: James Bottomley <jejb@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
diff --git a/include/asm-parisc/spinlock.h b/include/asm-parisc/spinlock.h
index 7c3f406..16c2ac0 100644
--- a/include/asm-parisc/spinlock.h
+++ b/include/asm-parisc/spinlock.h
@@ -11,18 +11,25 @@
return *a == 0;
}
-#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
+#define __raw_spin_lock(lock) __raw_spin_lock_flags(lock, 0)
#define __raw_spin_unlock_wait(x) \
do { cpu_relax(); } while (__raw_spin_is_locked(x))
-static inline void __raw_spin_lock(raw_spinlock_t *x)
+static inline void __raw_spin_lock_flags(raw_spinlock_t *x,
+ unsigned long flags)
{
volatile unsigned int *a;
mb();
a = __ldcw_align(x);
while (__ldcw(a) == 0)
- while (*a == 0);
+ while (*a == 0)
+ if (flags & PSW_SM_I) {
+ local_irq_enable();
+ cpu_relax();
+ local_irq_disable();
+ } else
+ cpu_relax();
mb();
}
@@ -60,26 +67,20 @@
static __inline__ void __raw_read_lock(raw_rwlock_t *rw)
{
- unsigned long flags;
- local_irq_save(flags);
__raw_spin_lock(&rw->lock);
rw->counter++;
__raw_spin_unlock(&rw->lock);
- local_irq_restore(flags);
}
static __inline__ void __raw_read_unlock(raw_rwlock_t *rw)
{
- unsigned long flags;
- local_irq_save(flags);
__raw_spin_lock(&rw->lock);
rw->counter--;
__raw_spin_unlock(&rw->lock);
- local_irq_restore(flags);
}
/* write_lock is less trivial. We optimistically grab the lock and check