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![Peter Zijlstra](/assets/img/avatar_default.png)
Because of a collision with 8d056c48e4
("CPU hotplug, smp: flush any
pending IPI callbacks before CPU offline"), which ends up calling
hotplug_cfd()->flush_smp_call_function_queue()->irq_work_run(), which
is not from IRQ context.
And since that already calls irq_work_run() from the hotplug path,
remove our entire hotplug handling.
Reported-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-busatzs2gvz4v62258agipuf@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
185 lines
4.2 KiB
C
185 lines
4.2 KiB
C
/*
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* Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*
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* Provides a framework for enqueueing and running callbacks from hardirq
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* context. The enqueueing is NMI-safe.
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*/
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#include <linux/bug.h>
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#include <linux/kernel.h>
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#include <linux/export.h>
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#include <linux/irq_work.h>
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#include <linux/percpu.h>
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#include <linux/hardirq.h>
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#include <linux/irqflags.h>
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#include <linux/sched.h>
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#include <linux/tick.h>
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#include <linux/cpu.h>
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#include <linux/notifier.h>
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#include <linux/smp.h>
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#include <asm/processor.h>
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static DEFINE_PER_CPU(struct llist_head, raised_list);
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static DEFINE_PER_CPU(struct llist_head, lazy_list);
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/*
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* Claim the entry so that no one else will poke at it.
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*/
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static bool irq_work_claim(struct irq_work *work)
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{
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unsigned long flags, oflags, nflags;
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/*
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* Start with our best wish as a premise but only trust any
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* flag value after cmpxchg() result.
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*/
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flags = work->flags & ~IRQ_WORK_PENDING;
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for (;;) {
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nflags = flags | IRQ_WORK_FLAGS;
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oflags = cmpxchg(&work->flags, flags, nflags);
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if (oflags == flags)
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break;
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if (oflags & IRQ_WORK_PENDING)
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return false;
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flags = oflags;
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cpu_relax();
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}
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return true;
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}
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void __weak arch_irq_work_raise(void)
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{
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/*
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* Lame architectures will get the timer tick callback
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*/
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}
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#ifdef CONFIG_SMP
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/*
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* Enqueue the irq_work @work on @cpu unless it's already pending
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* somewhere.
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*
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* Can be re-enqueued while the callback is still in progress.
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*/
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bool irq_work_queue_on(struct irq_work *work, int cpu)
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{
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/* All work should have been flushed before going offline */
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WARN_ON_ONCE(cpu_is_offline(cpu));
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/* Arch remote IPI send/receive backend aren't NMI safe */
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WARN_ON_ONCE(in_nmi());
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/* Only queue if not already pending */
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if (!irq_work_claim(work))
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return false;
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if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
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arch_send_call_function_single_ipi(cpu);
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return true;
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}
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EXPORT_SYMBOL_GPL(irq_work_queue_on);
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#endif
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/* Enqueue the irq work @work on the current CPU */
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bool irq_work_queue(struct irq_work *work)
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{
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/* Only queue if not already pending */
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if (!irq_work_claim(work))
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return false;
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/* Queue the entry and raise the IPI if needed. */
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preempt_disable();
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/* If the work is "lazy", handle it from next tick if any */
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if (work->flags & IRQ_WORK_LAZY) {
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if (llist_add(&work->llnode, &__get_cpu_var(lazy_list)) &&
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tick_nohz_tick_stopped())
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arch_irq_work_raise();
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} else {
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if (llist_add(&work->llnode, &__get_cpu_var(raised_list)))
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arch_irq_work_raise();
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}
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preempt_enable();
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return true;
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}
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EXPORT_SYMBOL_GPL(irq_work_queue);
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bool irq_work_needs_cpu(void)
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{
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struct llist_head *raised, *lazy;
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raised = &__get_cpu_var(raised_list);
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lazy = &__get_cpu_var(lazy_list);
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if (llist_empty(raised) && llist_empty(lazy))
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return false;
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/* All work should have been flushed before going offline */
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WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
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return true;
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}
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static void irq_work_run_list(struct llist_head *list)
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{
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unsigned long flags;
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struct irq_work *work;
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struct llist_node *llnode;
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BUG_ON(!irqs_disabled());
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if (llist_empty(list))
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return;
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llnode = llist_del_all(list);
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while (llnode != NULL) {
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work = llist_entry(llnode, struct irq_work, llnode);
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llnode = llist_next(llnode);
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/*
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* Clear the PENDING bit, after this point the @work
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* can be re-used.
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* Make it immediately visible so that other CPUs trying
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* to claim that work don't rely on us to handle their data
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* while we are in the middle of the func.
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*/
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flags = work->flags & ~IRQ_WORK_PENDING;
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xchg(&work->flags, flags);
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work->func(work);
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/*
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* Clear the BUSY bit and return to the free state if
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* no-one else claimed it meanwhile.
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*/
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(void)cmpxchg(&work->flags, flags, flags & ~IRQ_WORK_BUSY);
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}
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}
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/*
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* hotplug calls this through:
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* hotplug_cfd() -> flush_smp_call_function_queue()
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*/
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void irq_work_run(void)
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{
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irq_work_run_list(&__get_cpu_var(raised_list));
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irq_work_run_list(&__get_cpu_var(lazy_list));
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}
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EXPORT_SYMBOL_GPL(irq_work_run);
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/*
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* Synchronize against the irq_work @entry, ensures the entry is not
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* currently in use.
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*/
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void irq_work_sync(struct irq_work *work)
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{
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WARN_ON_ONCE(irqs_disabled());
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while (work->flags & IRQ_WORK_BUSY)
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cpu_relax();
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}
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EXPORT_SYMBOL_GPL(irq_work_sync);
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