diff options
Diffstat (limited to 'kernel/irq/handle.c')
| -rw-r--r-- | kernel/irq/handle.c | 76 |
1 files changed, 63 insertions, 13 deletions
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c index b110c83..517561f 100644 --- a/kernel/irq/handle.c +++ b/kernel/irq/handle.c @@ -51,6 +51,68 @@ static void warn_no_thread(unsigned int irq, struct irqaction *action) "but no thread function available.", irq, action->name); } +static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action) +{ + /* + * Wake up the handler thread for this action. In case the + * thread crashed and was killed we just pretend that we + * handled the interrupt. The hardirq handler has disabled the + * device interrupt, so no irq storm is lurking. If the + * RUNTHREAD bit is already set, nothing to do. + */ + if (test_bit(IRQTF_DIED, &action->thread_flags) || + test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags)) + return; + + /* + * It's safe to OR the mask lockless here. We have only two + * places which write to threads_oneshot: This code and the + * irq thread. + * + * This code is the hard irq context and can never run on two + * cpus in parallel. If it ever does we have more serious + * problems than this bitmask. + * + * The irq threads of this irq which clear their "running" bit + * in threads_oneshot are serialized via desc->lock against + * each other and they are serialized against this code by + * IRQS_INPROGRESS. + * + * Hard irq handler: + * + * spin_lock(desc->lock); + * desc->state |= IRQS_INPROGRESS; + * spin_unlock(desc->lock); + * set_bit(IRQTF_RUNTHREAD, &action->thread_flags); + * desc->threads_oneshot |= mask; + * spin_lock(desc->lock); + * desc->state &= ~IRQS_INPROGRESS; + * spin_unlock(desc->lock); + * + * irq thread: + * + * again: + * spin_lock(desc->lock); + * if (desc->state & IRQS_INPROGRESS) { + * spin_unlock(desc->lock); + * while(desc->state & IRQS_INPROGRESS) + * cpu_relax(); + * goto again; + * } + * if (!test_bit(IRQTF_RUNTHREAD, &action->thread_flags)) + * desc->threads_oneshot &= ~mask; + * spin_unlock(desc->lock); + * + * So either the thread waits for us to clear IRQS_INPROGRESS + * or we are waiting in the flow handler for desc->lock to be + * released before we reach this point. The thread also checks + * IRQTF_RUNTHREAD under desc->lock. If set it leaves + * threads_oneshot untouched and runs the thread another time. + */ + desc->threads_oneshot |= action->thread_mask; + wake_up_process(action->thread); +} + irqreturn_t handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) { @@ -85,19 +147,7 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) break; } - /* - * Wake up the handler thread for this - * action. In case the thread crashed and was - * killed we just pretend that we handled the - * interrupt. The hardirq handler above has - * disabled the device interrupt, so no irq - * storm is lurking. - */ - if (likely(!test_bit(IRQTF_DIED, - &action->thread_flags))) { - set_bit(IRQTF_RUNTHREAD, &action->thread_flags); - wake_up_process(action->thread); - } + irq_wake_thread(desc, action); /* Fall through to add to randomness */ case IRQ_HANDLED: |