Messages in this thread Patch in this message | | | Date | Thu, 31 May 2007 21:06:04 +0400 | From | Oleg Nesterov <> | Subject | Re: floppy.c soft lockup |
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On 05/31, Mark Hounschell wrote: > > Andrew Morton wrote: > > On Tue, 29 May 2007 13:31:05 -0400 Mark Hounschell <markh@compro.net> wrote: > > > >> Changes in floppy.c from 2.6.17 and 2.6.18 have broken an application I have. I have tracked > >> it down to a single line of code. When the following patch is applied to the version in 2.6.18 > >> my application works. > >> > >> --- linux-2.6.18/drivers/block/floppy.c 2006-09-19 23:42:06.000000000 -0400 > >> +++ linux-2.6.18-crt/drivers/block/floppy.c 2007-05-29 09:12:20.000000000 -0400 > >> @@ -893,7 +893,6 @@ > >> set_current_state(TASK_RUNNING); > >> remove_wait_queue(&fdc_wait, &wait); > >> > >> - flush_scheduled_work(); > >> } > >> command_status = FD_COMMAND_NONE; > >> > > Interesting. I'd expect that the calling process is spinning, with realtime > > policy and is expecting some other process to do something (ie: run a workqueue). > > > > If you keep the process and irq affinities, and disable the realtime policy > > does that also prevent the problem? > > > > Yes it does. > > > It would be interesting it you could capture a few task traces while it is stuck: > > echo 1 > /proc/sys/kernel/sysrq then do ALT-SYSRQ-P a bunch of times and ALT-SYSRQ-T, > > see if you can work out where the CPU is stuck. > > > > I've attached the syslog output as a result of doing the above. I can't really make any kind of > determination from it myself as I don't really knowing what I'm looking at.
Could you show the full output? There are no events/* or process doing ioctl() in sysrq.txt you attached.
> > ALso, 2.6.22-rc3 might have accidentally fixed this. > > > > No. Same thing there. The traces attached are using 2.6.22-rc3. > > Basically the main RT-process (which is a CPU bound process on processor-2) signals a > thread to do some I/O. That RT-thread (running on the other processor) does a simple
If the main RT-process monopolizes processor-2, flush_workqueue() (or cancel_work_sync()) can hang of course, we can do nothing.
> ioctl(Q->DevSpec1, FDSETPRM, &medprm) > > and there is no return from the call. That thread is hung.
What happens if you kill the main RT-process?
Could you try the patch below? Just to see if it makes any difference.
Oleg.
(against 2.6.22-rcX)
--- OLD/drivers/block/floppy.c~ 2007-04-03 13:04:58.000000000 +0400 +++ OLD/drivers/block/floppy.c 2007-05-31 20:50:18.000000000 +0400 @@ -862,6 +862,8 @@ static void set_fdc(int drive) FDCS->reset = 1; } +static DECLARE_WORK(floppy_work, NULL); + /* locks the driver */ static int _lock_fdc(int drive, int interruptible, int line) { @@ -893,7 +895,7 @@ static int _lock_fdc(int drive, int inte set_current_state(TASK_RUNNING); remove_wait_queue(&fdc_wait, &wait); - flush_scheduled_work(); + cancel_work_sync(&floppy_work); } command_status = FD_COMMAND_NONE; @@ -992,8 +994,6 @@ static void empty(void) { } -static DECLARE_WORK(floppy_work, NULL); - static void schedule_bh(void (*handler) (void)) { PREPARE_WORK(&floppy_work, (work_func_t)handler); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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