Messages in this thread | | | Date | Sun, 7 Jul 2002 19:13:32 +0200 (MET DST) | From | Bartlomiej Zolnierkiewicz <> | Subject | Re: ide__sti usage |
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On Sun, 7 Jul 2002, Zwane Mwaikambo wrote:
> Hi Bart, Martin > I'm seeing a number of deadlocks, most of them due to ide__sti > enabling interrupts in a critical section which needs to be protected > against interrupts too.
I'm seeing blue sky ;-) Which IDE patch?
> Another dangerous scenario is the following, from here the usage of > ide__sti becomes questionable. > > queue_commands() { > ide__sti(); > start_request(); > } > ... > start_request() { > spin_unlock_irq(); > frob_ide();
Whats that?
> spin_lock_irq(); > } > > and also; > > if (ch->unmask) > ide__sti(); /* local CPU only */ > > /* service this interrupt, may set handler for next interrupt */ > startstop = handler(drive, drive->rq); > spin_lock_irq(ch->lock); > > If someone can explain to me what ide__sti really is trying to achieve > i'd greatly appreciate it.
ide_sti() its just __sti() (except atari). Note that ide_do_request() is called under spin_lock_irqsave(ch->lock, flags). We have to unlock or we will get deadlock - imagine we are holding lock and we get irq (shared irq, unexpected one) and we try to lock in ata_irq_request() -> deadlock.
Also for most code in start_request() we dont need lock, we need it only for calling block layer helpers, changing/reading IDE_BUSY bit and ch->handler, timer and drive->rq.
Also we cannot disable interrupts, because we wont know when drive is interrupting us, missed irqs.
Please also read my previous mails to Alex...
Regards -- Bartlomiej
> Regards, > Zwane Mwaikambo > > -- > function.linuxpower.ca >
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