Messages in this thread Patch in this message |  | | | Date | Thu, 1 Dec 2011 22:23:22 +0100 (CET) | | From | Thomas Gleixner <> | | Subject | Re: [PATCH] irq: Fix race condition when stopping the irq thread |
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On Thu, 1 Dec 2011, Ido Yariv wrote:
> In irq_wait_for_interrupt(), the should_stop member is verified before > setting the task's state to TASK_INTERRUPTIBLE and calling schedule(). > In case kthread_stop sets should_stop and wakes up the process after > should_stop is checked by the irq thread but before the task's state is > changed, the irq thread might never exit: > > kthread_stop irq_wait_for_interrupt > ------------ ---------------------- > > ... > ... while (!kthread_should_stop()) { > kthread->should_stop = 1; > wake_up_process(k); > wait_for_completion(&kthread->exited); > ... > set_current_state(TASK_INTERRUPTIBLE); > > ... > > schedule(); > } > ... > > Fix this by checking if the thread should stop after modifying the > task's state.
Good catch! I restructure it to:
--- tip.orig/kernel/irq/manage.c +++ tip/kernel/irq/manage.c @@ -623,8 +623,9 @@ static irqreturn_t irq_nested_primary_ha static int irq_wait_for_interrupt(struct irqaction *action) { + set_current_state(TASK_INTERRUPTIBLE); + while (!kthread_should_stop()) { - set_current_state(TASK_INTERRUPTIBLE); if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)) { @@ -632,7 +633,9 @@ static int irq_wait_for_interrupt(struct return 0; } schedule(); + set_current_state(TASK_INTERRUPTIBLE); } + __set_current_state(TASK_RUNNING); return -1; } That saves us the extra conditional in the loop. Thanks,
tglx
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