From 44eb2c6fd2aca52bf7249bb8edfbd7e8853b1033 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 13 Nov 2011 17:17:09 +0100 Subject: [PATCH] softirq: Check preemption after reenabling interrupts raise_softirq_irqoff() disables interrupts and wakes the softirq daemon, but after reenabling interrupts there is no preemption check, so the execution of the softirq thread might be delayed arbitrarily. In principle we could add that check to local_irq_enable/restore, but that's overkill as the rasie_softirq_irqoff() sections are the only ones which show this behaviour. Reported-by: Carsten Emde Signed-off-by: Thomas Gleixner Cc: stable-rt@vger.kernel.org --- block/blk-iopoll.c | 3 +++ block/blk-softirq.c | 3 +++ include/linux/preempt.h | 3 +++ net/core/dev.c | 6 ++++++ 4 files changed, 15 insertions(+) diff --git a/block/blk-iopoll.c b/block/blk-iopoll.c index 1855bf51edb0..bdc839ac25d5 100644 --- a/block/blk-iopoll.c +++ b/block/blk-iopoll.c @@ -38,6 +38,7 @@ void blk_iopoll_sched(struct blk_iopoll *iop) list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll)); __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ); local_irq_restore(flags); + preempt_check_resched_rt(); } EXPORT_SYMBOL(blk_iopoll_sched); @@ -135,6 +136,7 @@ static void blk_iopoll_softirq(struct softirq_action *h) __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ); local_irq_enable(); + preempt_check_resched_rt(); } /** @@ -204,6 +206,7 @@ static int blk_iopoll_cpu_notify(struct notifier_block *self, this_cpu_ptr(&blk_cpu_iopoll)); __raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ); local_irq_enable(); + preempt_check_resched_rt(); } return NOTIFY_OK; diff --git a/block/blk-softirq.c b/block/blk-softirq.c index 57790c1a97eb..9093070d32e9 100644 --- a/block/blk-softirq.c +++ b/block/blk-softirq.c @@ -51,6 +51,7 @@ static void trigger_softirq(void *data) raise_softirq_irqoff(BLOCK_SOFTIRQ); local_irq_restore(flags); + preempt_check_resched_rt(); } /* @@ -93,6 +94,7 @@ static int blk_cpu_notify(struct notifier_block *self, unsigned long action, this_cpu_ptr(&blk_cpu_done)); raise_softirq_irqoff(BLOCK_SOFTIRQ); local_irq_enable(); + preempt_check_resched_rt(); } return NOTIFY_OK; @@ -150,6 +152,7 @@ do_local: goto do_local; local_irq_restore(flags); + preempt_check_resched_rt(); } /** diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 11df024a2175..fb1ae0de888d 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -51,8 +51,10 @@ do { \ #ifdef CONFIG_PREEMPT_RT_BASE # define preempt_enable_no_resched() sched_preempt_enable_no_resched() +# define preempt_check_resched_rt() preempt_check_resched() #else # define preempt_enable_no_resched() preempt_enable() +# define preempt_check_resched_rt() barrier(); #endif #ifdef CONFIG_PREEMPT @@ -127,6 +129,7 @@ do { \ #define preempt_disable_notrace() barrier() #define preempt_enable_no_resched_notrace() barrier() #define preempt_enable_notrace() barrier() +#define preempt_check_resched_rt() barrier() #endif /* CONFIG_PREEMPT_COUNT */ diff --git a/net/core/dev.c b/net/core/dev.c index 8d49133bbbe7..9bdbc6ea240c 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2154,6 +2154,7 @@ static inline void __netif_reschedule(struct Qdisc *q) sd->output_queue_tailp = &q->next_sched; raise_softirq_irqoff(NET_TX_SOFTIRQ); local_irq_restore(flags); + preempt_check_resched_rt(); } void __netif_schedule(struct Qdisc *q) @@ -2188,6 +2189,7 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason) __this_cpu_write(softnet_data.completion_queue, skb); raise_softirq_irqoff(NET_TX_SOFTIRQ); local_irq_restore(flags); + preempt_check_resched_rt(); } EXPORT_SYMBOL(__dev_kfree_skb_irq); @@ -3245,6 +3247,7 @@ enqueue: rps_unlock(sd); local_irq_restore(flags); + preempt_check_resched_rt(); atomic_long_inc(&skb->dev->rx_dropped); kfree_skb(skb); @@ -4196,6 +4199,7 @@ static void net_rps_action_and_irq_enable(struct softnet_data *sd) } else #endif local_irq_enable(); + preempt_check_resched_rt(); } static int process_backlog(struct napi_struct *napi, int quota) @@ -4268,6 +4272,7 @@ void __napi_schedule(struct napi_struct *n) local_irq_save(flags); ____napi_schedule(&__get_cpu_var(softnet_data), n); local_irq_restore(flags); + preempt_check_resched_rt(); } EXPORT_SYMBOL(__napi_schedule); @@ -6876,6 +6881,7 @@ static int dev_cpu_callback(struct notifier_block *nfb, raise_softirq_irqoff(NET_TX_SOFTIRQ); local_irq_enable(); + preempt_check_resched_rt(); /* Process offline CPU's input_pkt_queue */ while ((skb = __skb_dequeue(&oldsd->process_queue))) {