Mathew Kanner <[EMAIL PROTECTED]> wrote: > On Nov 25, Don Lewis wrote: > > On 25 Nov, Don Lewis wrote: > > > On 25 Nov, Artur Poplawski wrote: > > >> Artur Poplawski <[EMAIL PROTECTED]> wrote: > > >> > > >>> Hello, > > >>> > > >>> > > >>> > > >>> On a 5.1-RELEASE and 5.2-BETA machines I have been able to cause a panic > > >>> like this: > > > > > >>> Sleeping on "swread" with the following non-sleepable locks held: > > >>> exclusive sleep mutex pcm0:play:0 (pcm channel) r = 0 (0xc1c3d740) locked @ \ > > >>> > > >>> /usr/src/sys/dev/sound/pcm/dsp.c:146 > > > > > > This enables the panic. > > > > > >>> panic: sleeping thread (pid 583) owns a non-sleepable lock > > > > > > Then the panic happens when another thread tries to grab the mutex. > > > > > > > > > The problem is that the pcm code attempts to hold a mutex across a call > > > to uiomove(), which can sleep if the userland buffer that it is trying > > > to access is paged out. Either the buffer has to be pre-wired before > > > calling getchns(), or the mutex has to be dropped around the call to > > > uiomove(). The amount of memory to be wired should be limited to > > > 'sz' as calculated by chn_read() and chn_write(), which complicates the > > > logic. Dropping the mutex probably has other issues. > > > > Following up to myself ... > > > > It might be safe to drop the mutex for the uiomove() call if the code > > set flags to enforce a limit of one reader and one writer at a time to > > keep the code from being re-entered. The buffer pointer manipulations > > in sndbuf_dispose() and sndbuf_acquire() would probably still have to be > > protected by the mutex. If this can be made to work, it would probably > > be preferable to wiring the buffer. It would have a lot less CPU > > overhead, and would work better with large buffers, which could still be > > allowed to page normally. > > Don, > I never would have suspected that uio might sleep and panic, > thanks for the clue. > > Artur, > Could you try the attached patch.
I've tried the patch -- and it works great! :-) I was unable to trigger the panic with the patch applied, although I tried really hard -- so I guess the problem is solved. Mat and Don, I'm really very thankful for your help. Best regards, Artur _______________________________________________ [EMAIL PROTECTED] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "[EMAIL PROTECTED]"
