diff options
| -rw-r--r-- | arch/x86/xen/spinlock.c | 65 | ||||
| -rw-r--r-- | drivers/xen/events.c | 25 | ||||
| -rw-r--r-- | include/xen/events.h | 2 |
3 files changed, 77 insertions, 15 deletions
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 8dc4d31da67..4884bc603aa 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -47,25 +47,41 @@ static int xen_spin_trylock(struct raw_spinlock *lock) static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners); -static inline void spinning_lock(struct xen_spinlock *xl) +/* + * Mark a cpu as interested in a lock. Returns the CPU's previous + * lock of interest, in case we got preempted by an interrupt. + */ +static inline struct xen_spinlock *spinning_lock(struct xen_spinlock *xl) { + struct xen_spinlock *prev; + + prev = __get_cpu_var(lock_spinners); __get_cpu_var(lock_spinners) = xl; + wmb(); /* set lock of interest before count */ + asm(LOCK_PREFIX " incw %0" : "+m" (xl->spinners) : : "memory"); + + return prev; } -static inline void unspinning_lock(struct xen_spinlock *xl) +/* + * Mark a cpu as no longer interested in a lock. Restores previous + * lock of interest (NULL for none). + */ +static inline void unspinning_lock(struct xen_spinlock *xl, struct xen_spinlock *prev) { asm(LOCK_PREFIX " decw %0" : "+m" (xl->spinners) : : "memory"); - wmb(); /* decrement count before clearing lock */ - __get_cpu_var(lock_spinners) = NULL; + wmb(); /* decrement count before restoring lock */ + __get_cpu_var(lock_spinners) = prev; } static noinline int xen_spin_lock_slow(struct raw_spinlock *lock) { struct xen_spinlock *xl = (struct xen_spinlock *)lock; + struct xen_spinlock *prev; int irq = __get_cpu_var(lock_kicker_irq); int ret; @@ -74,23 +90,42 @@ static noinline int xen_spin_lock_slow(struct raw_spinlock *lock) return 0; /* announce we're spinning */ - spinning_lock(xl); + prev = spinning_lock(xl); - /* clear pending */ - xen_clear_irq_pending(irq); + do { + /* clear pending */ + xen_clear_irq_pending(irq); + + /* check again make sure it didn't become free while + we weren't looking */ + ret = xen_spin_trylock(lock); + if (ret) { + /* + * If we interrupted another spinlock while it + * was blocking, make sure it doesn't block + * without rechecking the lock. + */ + if (prev != NULL) + xen_set_irq_pending(irq); + goto out; + } - /* check again make sure it didn't become free while - we weren't looking */ - ret = xen_spin_trylock(lock); - if (ret) - goto out; + /* + * Block until irq becomes pending. If we're + * interrupted at this point (after the trylock but + * before entering the block), then the nested lock + * handler guarantees that the irq will be left + * pending if there's any chance the lock became free; + * xen_poll_irq() returns immediately if the irq is + * pending. + */ + xen_poll_irq(irq); + } while (!xen_test_irq_pending(irq)); /* check for spurious wakeups */ - /* block until irq becomes pending */ - xen_poll_irq(irq); kstat_this_cpu.irqs[irq]++; out: - unspinning_lock(xl); + unspinning_lock(xl, prev); return ret; } diff --git a/drivers/xen/events.c b/drivers/xen/events.c index a0837036d89..b6c2b8f16be 100644 --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -164,6 +164,12 @@ static inline void set_evtchn(int port) sync_set_bit(port, &s->evtchn_pending[0]); } +static inline int test_evtchn(int port) +{ + struct shared_info *s = HYPERVISOR_shared_info; + return sync_test_bit(port, &s->evtchn_pending[0]); +} + /** * notify_remote_via_irq - send event to remote end of event channel via irq @@ -732,6 +738,25 @@ void xen_clear_irq_pending(int irq) clear_evtchn(evtchn); } +void xen_set_irq_pending(int irq) +{ + int evtchn = evtchn_from_irq(irq); + + if (VALID_EVTCHN(evtchn)) + set_evtchn(evtchn); +} + +bool xen_test_irq_pending(int irq) +{ + int evtchn = evtchn_from_irq(irq); + bool ret = false; + + if (VALID_EVTCHN(evtchn)) + ret = test_evtchn(evtchn); + + return ret; +} + /* Poll waiting for an irq to become pending. In the usual case, the irq will be disabled so it won't deliver an interrupt. */ void xen_poll_irq(int irq) diff --git a/include/xen/events.h b/include/xen/events.h index 4680ff3fbc9..0d5f1adc036 100644 --- a/include/xen/events.h +++ b/include/xen/events.h @@ -46,6 +46,8 @@ extern void xen_irq_resume(void); /* Clear an irq's pending state, in preparation for polling on it */ void xen_clear_irq_pending(int irq); +void xen_set_irq_pending(int irq); +bool xen_test_irq_pending(int irq); /* Poll waiting for an irq to become pending. In the usual case, the irq will be disabled so it won't deliver an interrupt. */ |