Re: 2.5.50: sleeping function called from illegal context

[Takashi Iwai <tiwai@suse.de>]

At Tue, 3 Dec 2002 13:21:41 +0100,
Duncan Sands wrote:
> 
> On Tuesday 03 December 2002 19:34, Paul Davis wrote:
> > >I guess another way of dealing with this kind of problem is to use a
> > >semaphore rather than a spinlock, and a workqueue: when the interrupt
> > >comes in, the call to snd_ctl_notify is put on the queue, where it will
> > > later be run in process context, and can safely take the semaphore.
> >
> > can i get a pointer to some code that does this? we need to do this
> > for handling MIDI I/O in the hammerfall dsp driver. doing it from
> > the interrupt handler causes audio dropouts because the midi i/o is so
> > much slower.
> 
> For the use of workqueues (introduced in 2.5), see
> http://lwn.net/Articles/11360/
> and
> http://lwn.net/Articles/10963/

thanks for pointers!

i believe the tasklet would be enough for a task like the midi
handler, too.


regarding to the workqueue, it can be used for a new stuff to shutdown
the module asynchronously for hotplug, which Jaroslav added recently.
the current implementation is invoking a kernel thread directly.
with the workqueue, the code would be much simpler (although there is
another issue for compatibility with older kernels :)


Takashi


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