From 08dc2ca61e683e9119ff534dfcd0fd555401fcf7 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Thu, 17 Nov 2005 16:35:09 -0500 Subject: [PATCH] [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 Signed-off-by: Kyle McMartin --- include/asm-parisc/spinlock.h | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/include/asm-parisc/spinlock.h b/include/asm-parisc/spinlock.h index 7c3f406a746a..16c2ac075fc5 100644 --- a/include/asm-parisc/spinlock.h +++ b/include/asm-parisc/spinlock.h @@ -11,18 +11,25 @@ static inline int __raw_spin_is_locked(raw_spinlock_t *x) 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 int __raw_spin_trylock(raw_spinlock_t *x) 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 -- 2.30.2