Re: manipulating sigmask from filesystems and drivers

From: Pete Zaitcev (
Date: Thu Aug 01 2002 - 18:37:20 EST

>> They should be waiting in TASK_UNINTERRUPTIBLE, and we should add a
>> flag to distinguish between "increases load average" and "doesn't".
> The disadvantage of this approach is that it encourages people to be lazy
> and sleep with signals disabled, instead of implementing proper cleanup
> code.
> I'm more in favour of removing TASK_UNINTERRUPTIBLE entirely, or at least
> making people apply for a special licence to be permitted to use it :)
> --
> dwmw2

Consider this. An application writes to /dev/dsp0, and ymfpci
(for example) start DMA. Then user interrupts the app with ^C.
When ymfpci gets ->release() call, it has to tell the chip
to stop DMA, then wait until it's complete. If it tries to
wait with TASK_INTERRUPTIBLE, schedule() will return immediately,
and in essense do a busy loop with CPU pegged at 100%.

Same thing happens in USB, only there it's worse: a spinning
application locks out khubd and whole subsistem dies.

-- Pete
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