Messages in this thread | | | From | Michael Buesch <> | Subject | Re: Threaded interrupt handlers broken? | Date | Sun, 16 Aug 2009 12:14:36 +0200 |
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On Sunday 16 August 2009 11:53:13 Michael Buesch wrote: > Hi, > > I was trying to use threaded interrupt handlers, but the code always crashes > within irq_thread() with a "BUG: spinlock bad magic 00000000". > The spinlock that's not properly initialized is from the wait_for_threads waitqueue. > It crashes on line 526 (see below). > The initialization of the waitqueue struct seems to depend on whether the IRQ is > shared or not. I don't know if that's correct, but I patched it to unconditionally > initialize the struct. That did not help. > > Any ideas? > > > 490 static int irq_thread(void *data) > 491 { > 492 struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2, }; > 493 struct irqaction *action = data; > 494 struct irq_desc *desc = irq_to_desc(action->irq); > 495 int wake; > 496 > 497 sched_setscheduler(current, SCHED_FIFO, ¶m); > 498 current->irqaction = action; > 499 > 500 while (!irq_wait_for_interrupt(action)) { > 501 > 502 irq_thread_check_affinity(desc, action); > 503 > 504 atomic_inc(&desc->threads_active); > 505 > 506 spin_lock_irq(&desc->lock); > 507 if (unlikely(desc->status & IRQ_DISABLED)) { > 508 /* > 509 * CHECKME: We might need a dedicated > 510 * IRQ_THREAD_PENDING flag here, which > 511 * retriggers the thread in check_irq_resend() > 512 * but AFAICT IRQ_PENDING should be fine as it > 513 * retriggers the interrupt itself --- tglx > 514 */ > 515 desc->status |= IRQ_PENDING; > 516 spin_unlock_irq(&desc->lock); > 517 } else { > 518 spin_unlock_irq(&desc->lock); > 519 > 520 action->thread_fn(action->irq, action->dev_id); > 521 } > 522 > 523 wake = atomic_dec_and_test(&desc->threads_active);
Is this test logic inverted? atomic_dec_and_test() means (threads_active - 1) == 0 Shouldn't it be like this? (threads_active - 1) != 0
> 524 > 525 if (wake && waitqueue_active(&desc->wait_for_threads)) > 526 wake_up(&desc->wait_for_threads); <<<<<<<<<<<<<<<<<<<<<<<< > 527 } > 528 > 529 /* > 530 * Clear irqaction. Otherwise exit_irq_thread() would make > 531 * fuzz about an active irq thread going into nirvana. > 532 */ > 533 current->irqaction = NULL; > 534 return 0; > 535 } >
-- Greetings, Michael.
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