genirq: Get rid of unnecessary IRQTF_DIED flag
Currently IRQTF_DIED flag is set when a IRQ thread handler calls do_exit() But also PF_EXITING per process flag gets set when a thread exits. This fix eliminates the duplicate by using PF_EXITING flag. Also, there is a race condition in exit_irq_thread(). In case a thread's bit is cleared in desc->threads_oneshot (and the IRQ line gets unmasked), but before IRQTF_DIED flag is set, a new interrupt might come in and set just cleared bit again, this time forever. This fix throws IRQTF_DIED flag away, eliminating the race as a result. [ tglx: Test THREAD_EXITING first as suggested by Oleg ] Reported-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Alexander Gordeev <agordeev@redhat.com> Link: http://lkml.kernel.org/r/20120309135958.GD2114@dhcp-26-207.brq.redhat.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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4 changed files with 4 additions and 15 deletions
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@ -935,8 +935,6 @@ void do_exit(long code)
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schedule();
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}
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exit_irq_thread();
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exit_signals(tsk); /* sets PF_EXITING */
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/*
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* tsk->flags are checked in the futex code to protect against
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@ -945,6 +943,8 @@ void do_exit(long code)
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smp_mb();
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raw_spin_unlock_wait(&tsk->pi_lock);
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exit_irq_thread();
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if (unlikely(in_atomic()))
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printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",
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current->comm, task_pid_nr(current),
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@ -60,7 +60,7 @@ static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
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* device interrupt, so no irq storm is lurking. If the
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* RUNTHREAD bit is already set, nothing to do.
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*/
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if (test_bit(IRQTF_DIED, &action->thread_flags) ||
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if ((action->thread->flags & PF_EXITING) ||
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test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))
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return;
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@ -20,14 +20,12 @@ extern bool noirqdebug;
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/*
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* Bits used by threaded handlers:
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* IRQTF_RUNTHREAD - signals that the interrupt handler thread should run
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* IRQTF_DIED - handler thread died
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* IRQTF_WARNED - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed
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* IRQTF_AFFINITY - irq thread is requested to adjust affinity
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* IRQTF_FORCED_THREAD - irq action is force threaded
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*/
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enum {
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IRQTF_RUNTHREAD,
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IRQTF_DIED,
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IRQTF_WARNED,
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IRQTF_AFFINITY,
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IRQTF_FORCED_THREAD,
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@ -845,17 +845,8 @@ void exit_irq_thread(void)
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desc = irq_to_desc(action->irq);
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/*
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* Prevent a stale desc->threads_oneshot. Must be called
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* before setting the IRQTF_DIED flag.
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*/
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/* Prevent a stale desc->threads_oneshot */
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irq_finalize_oneshot(desc, action, true);
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/*
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* Set the THREAD DIED flag to prevent further wakeups of the
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* soon to be gone threaded handler.
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*/
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set_bit(IRQTF_DIED, &action->flags);
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}
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static void irq_setup_forced_threading(struct irqaction *new)
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