In order to be able to call set_task_cpu() without holding the appropriate rq->lock during ttwu(), add a TASK_WAKING clause to the task_rq_lock() primitive. Signed-off-by: Peter Zijlstra --- kernel/sched.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -928,12 +928,13 @@ static inline void finish_lock_switch(st #endif /* __ARCH_WANT_UNLOCKED_CTXSW */ /* - * Check whether the task is waking, we use this to synchronize ->cpus_allowed - * against ttwu(). + * In order to be able to call set_task_cpu() without holding the current + * task_rq(p)->lock during wake-ups we need to serialize on something else, + * use the wakeup task state. */ static inline int task_is_waking(struct task_struct *p) { - return unlikely(p->state == TASK_WAKING); + return p->state == TASK_WAKING; } /* @@ -948,7 +949,7 @@ static inline struct rq *__task_rq_lock( for (;;) { rq = task_rq(p); raw_spin_lock(&rq->lock); - if (likely(rq == task_rq(p))) + if (likely(rq == task_rq(p) && !task_is_waking(p))) return rq; raw_spin_unlock(&rq->lock); } @@ -956,8 +957,7 @@ static inline struct rq *__task_rq_lock( /* * task_rq_lock - lock the runqueue a given task resides on and disable - * interrupts. Note the ordering: we can safely lookup the task_rq without - * explicitly disabling preemption. + * interrupts. */ static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags) __acquires(rq->lock) @@ -968,7 +968,7 @@ static struct rq *task_rq_lock(struct ta local_irq_save(*flags); rq = task_rq(p); raw_spin_lock(&rq->lock); - if (likely(rq == task_rq(p))) + if (likely(rq == task_rq(p) && !task_is_waking(p))) return rq; raw_spin_unlock_irqrestore(&rq->lock, *flags); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/