Re: manipulating sigmask from filesystems and drivers

[Pete Zaitcev <zaitcev@redhat.com>]

>>  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