Messages in this thread Patch in this message | | | Date | Wed, 25 Aug 2004 13:17:07 +0200 | From | Takashi Iwai <> | Subject | Re: [PATCH] Fix shared interrupt handling of SA_INTERRUPT and SA_SAMPLE_RANDOM |
| |
At Tue, 24 Aug 2004 20:45:08 -0700, Andrew Morton wrote: > > Takashi Iwai <tiwai@suse.de> wrote: > > > > while the recent investation of latency issues, Thomas Charbonne > > suggested that there is a long-standing bug in the irq handler. > > When the irq is shared, SA_INTERRUPT flag is checked only for the > > first registered handler. When it's without SA_INTERRUPT, always > > local_irq_enable() is called even if the second or later handler has > > SA_INTERRUPT. > > That's because SA_INTERRUPT interrupts shouldn't be shared. The grey cell > which remembered why this is so seems to have died, but I've put the email > thread here: http://www.zip.com.au/~akpm/linux/patches/stuff/x.txt
Oh thanks that helps to understand what happened. (BTW, regarding the atomicity in that discussion: could the code like rtc.c (assuming it has also SA_SHIRQ) really cause deadlock?)
Anyway, suppressing the unnecessary call of add_interrupt_randomness() should be still valid. The reduced patch is below.
Takashi
--- linux-2.6.8.1/arch/i386/kernel/irq.c-dist 2004-08-25 13:13:05.153227112 +0200 +++ linux-2.6.8.1/arch/i386/kernel/irq.c 2004-08-25 13:13:34.760726088 +0200 @@ -220,14 +220,16 @@ asmlinkage int handle_IRQ_event(unsigned struct pt_regs *regs, struct irqaction *action) { int status = 1; /* Force the "do bottom halves" bit */ - int retval = 0; + int ret, retval = 0; if (!(action->flags & SA_INTERRUPT)) local_irq_enable(); do { - status |= action->flags; - retval |= action->handler(irq, action->dev_id, regs); + ret = action->handler(irq, action->dev_id, regs); + if (ret) + status |= action->flags; + retval |= ret; action = action->next; } while (action); if (status & SA_SAMPLE_RANDOM) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |