155 lines
4.5 KiB
Diff
155 lines
4.5 KiB
Diff
Subject: softirq: Check preemption after reenabling interrupts
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Sun, 13 Nov 2011 17:17:09 +0100 (CET)
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4-rt3.tar.xz
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raise_softirq_irqoff() disables interrupts and wakes the softirq
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daemon, but after reenabling interrupts there is no preemption check,
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so the execution of the softirq thread might be delayed arbitrarily.
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In principle we could add that check to local_irq_enable/restore, but
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that's overkill as the rasie_softirq_irqoff() sections are the only
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ones which show this behaviour.
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Reported-by: Carsten Emde <cbe@osadl.org>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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block/blk-iopoll.c | 3 +++
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block/blk-softirq.c | 3 +++
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include/linux/preempt.h | 3 +++
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net/core/dev.c | 7 +++++++
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4 files changed, 16 insertions(+)
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--- a/block/blk-iopoll.c
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+++ b/block/blk-iopoll.c
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@@ -35,6 +35,7 @@ void blk_iopoll_sched(struct blk_iopoll
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list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
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__raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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EXPORT_SYMBOL(blk_iopoll_sched);
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@@ -132,6 +133,7 @@ static void blk_iopoll_softirq(struct so
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__raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_enable();
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+ preempt_check_resched_rt();
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}
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/**
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@@ -201,6 +203,7 @@ static int blk_iopoll_cpu_notify(struct
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this_cpu_ptr(&blk_cpu_iopoll));
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__raise_softirq_irqoff(BLOCK_IOPOLL_SOFTIRQ);
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local_irq_enable();
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+ preempt_check_resched_rt();
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}
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return NOTIFY_OK;
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--- a/block/blk-softirq.c
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+++ b/block/blk-softirq.c
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@@ -51,6 +51,7 @@ static void trigger_softirq(void *data)
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raise_softirq_irqoff(BLOCK_SOFTIRQ);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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/*
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@@ -93,6 +94,7 @@ static int blk_cpu_notify(struct notifie
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this_cpu_ptr(&blk_cpu_done));
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raise_softirq_irqoff(BLOCK_SOFTIRQ);
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local_irq_enable();
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+ preempt_check_resched_rt();
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}
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return NOTIFY_OK;
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@@ -150,6 +152,7 @@ void __blk_complete_request(struct reque
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goto do_local;
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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/**
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--- a/include/linux/preempt.h
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+++ b/include/linux/preempt.h
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@@ -160,8 +160,10 @@ do { \
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#ifdef CONFIG_PREEMPT_RT_BASE
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# define preempt_enable_no_resched() sched_preempt_enable_no_resched()
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+# define preempt_check_resched_rt() preempt_check_resched()
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#else
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# define preempt_enable_no_resched() preempt_enable()
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+# define preempt_check_resched_rt() barrier();
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#endif
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#define preemptible() (preempt_count() == 0 && !irqs_disabled())
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@@ -232,6 +234,7 @@ do { \
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#define preempt_disable_notrace() barrier()
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#define preempt_enable_no_resched_notrace() barrier()
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#define preempt_enable_notrace() barrier()
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+#define preempt_check_resched_rt() barrier()
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#define preemptible() 0
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#endif /* CONFIG_PREEMPT_COUNT */
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -2246,6 +2246,7 @@ static inline void __netif_reschedule(st
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sd->output_queue_tailp = &q->next_sched;
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raise_softirq_irqoff(NET_TX_SOFTIRQ);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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void __netif_schedule(struct Qdisc *q)
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@@ -2327,6 +2328,7 @@ void __dev_kfree_skb_irq(struct sk_buff
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__this_cpu_write(softnet_data.completion_queue, skb);
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raise_softirq_irqoff(NET_TX_SOFTIRQ);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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EXPORT_SYMBOL(__dev_kfree_skb_irq);
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@@ -3519,6 +3521,7 @@ static int enqueue_to_backlog(struct sk_
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rps_unlock(sd);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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atomic_long_inc(&skb->dev->rx_dropped);
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kfree_skb(skb);
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@@ -4507,6 +4510,7 @@ static void net_rps_action_and_irq_enabl
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sd->rps_ipi_list = NULL;
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local_irq_enable();
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+ preempt_check_resched_rt();
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/* Send pending IPI's to kick RPS processing on remote cpus. */
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while (remsd) {
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@@ -4520,6 +4524,7 @@ static void net_rps_action_and_irq_enabl
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} else
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#endif
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local_irq_enable();
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+ preempt_check_resched_rt();
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}
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static bool sd_has_rps_ipi_waiting(struct softnet_data *sd)
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@@ -4601,6 +4606,7 @@ void __napi_schedule(struct napi_struct
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local_irq_save(flags);
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____napi_schedule(this_cpu_ptr(&softnet_data), n);
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local_irq_restore(flags);
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+ preempt_check_resched_rt();
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}
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EXPORT_SYMBOL(__napi_schedule);
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@@ -7449,6 +7455,7 @@ static int dev_cpu_callback(struct notif
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raise_softirq_irqoff(NET_TX_SOFTIRQ);
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local_irq_enable();
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+ preempt_check_resched_rt();
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/* Process offline CPU's input_pkt_queue */
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while ((skb = __skb_dequeue(&oldsd->process_queue))) {
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