[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 1/4] x86/IRQ: don't keep EOI timer running without need
The timer needs to remain active only until all pending IRQ instances have seen EOIs from their respective domains. Stop it when the in-flight count has reached zero in desc_guest_eoi(). Note that this is race free (with __do_IRQ_guest()), as the IRQ descriptor lock is being held at that point. Also pull up stopping of the timer in __do_IRQ_guest() itself: Instead of stopping it immediately before re-setting, stop it as soon as we've made it past any early returns from the function (and hence we're sure it'll get set again). Finally bail from the actual timer handler in case we find the timer already active again by the time we've managed to acquire the IRQ descriptor lock. Without this we may forcibly EOI an IRQ immediately after it got sent to a guest. For this, timer_is_active() gets split out of active_timer(), deliberately moving just one of the two ASSERT()s (to allow the function to be used also on a never initialized timer). Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/irq.c +++ b/xen/arch/x86/irq.c @@ -1115,6 +1115,9 @@ static void irq_guest_eoi_timer_fn(void action = (irq_guest_action_t *)desc->action; + if ( timer_is_active(&action->eoi_timer) ) + goto out; + if ( action->ack_type != ACKTYPE_NONE ) { unsigned int i; @@ -1167,6 +1170,9 @@ static void __do_IRQ_guest(int irq) return; } + if ( action->ack_type != ACKTYPE_NONE ) + stop_timer(&action->eoi_timer); + if ( action->ack_type == ACKTYPE_EOI ) { sp = pending_eoi_sp(peoi); @@ -1194,7 +1200,6 @@ static void __do_IRQ_guest(int irq) if ( action->ack_type != ACKTYPE_NONE ) { - stop_timer(&action->eoi_timer); migrate_timer(&action->eoi_timer, smp_processor_id()); set_timer(&action->eoi_timer, NOW() + MILLISECS(1)); } @@ -1457,6 +1462,8 @@ void desc_guest_eoi(struct irq_desc *des return; } + stop_timer(&action->eoi_timer); + if ( action->ack_type == ACKTYPE_UNMASK ) { ASSERT(cpumask_empty(action->cpu_eoi_map)); --- a/xen/common/timer.c +++ b/xen/common/timer.c @@ -282,11 +282,10 @@ static inline void timer_unlock(struct t }) -static bool_t active_timer(struct timer *timer) +static bool active_timer(const struct timer *timer) { ASSERT(timer->status >= TIMER_STATUS_inactive); - ASSERT(timer->status <= TIMER_STATUS_in_list); - return (timer->status >= TIMER_STATUS_in_heap); + return timer_is_active(timer); } --- a/xen/include/xen/timer.h +++ b/xen/include/xen/timer.h @@ -75,6 +75,19 @@ bool timer_expires_before(struct timer * #define timer_is_expired(t) timer_expires_before(t, NOW()) +/* + * True if a timer is active. + * + * Unlike for timer_expires_before(), it is the caller's responsibility to + * use suitable locking such that the returned value isn't stale by the time + * it gets acted upon. + */ +static inline bool timer_is_active(const struct timer *timer) +{ + ASSERT(timer->status <= TIMER_STATUS_in_list); + return timer->status >= TIMER_STATUS_in_heap; +} + /* Migrate a timer to a different CPU. The timer may be currently active. */ void migrate_timer(struct timer *timer, unsigned int new_cpu); _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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