svn commit: r326964 - head/sys/cam
Mark Johnston
markj at freebsd.org
Wed Jan 10 20:35:19 UTC 2018
On Wed, Jan 10, 2018 at 01:32:29PM -0700, Warner Losh wrote:
> On Wed, Jan 10, 2018 at 1:24 PM, Mark Johnston <markj at freebsd.org> wrote:
>
> > On Tue, Dec 19, 2017 at 04:13:22AM +0000, Warner Losh wrote:
> > > Author: imp
> > > Date: Tue Dec 19 04:13:22 2017
> > > New Revision: 326964
> > > URL: https://svnweb.freebsd.org/changeset/base/326964
> > >
> > > Log:
> > > When doing a dump, the scheduler is normally not running, so this
> > > changed worked to capture dumps for me. However, the test for
> > > SCHEDULER_STOPPED() isn't right. We can also call the dump routine
> > > from ddb, in which case the scheduler is still running. This leads to
> > > an assertion panic that we're sleeping when we shouldn't. Instead, use
> > > the proper test for dumping or not. This brings us in line with other
> > > places that do special things while we're doing polled I/O like this.
> > >
> > > Noticed by: pho@
> > > Differential Revision: https://reviews.freebsd.org/D13531
> > >
> > > Modified:
> > > head/sys/cam/cam_periph.c
> > >
> > > Modified: head/sys/cam/cam_periph.c
> > > ============================================================
> > ==================
> > > --- head/sys/cam/cam_periph.c Tue Dec 19 04:06:07 2017 (r326963)
> > > +++ head/sys/cam/cam_periph.c Tue Dec 19 04:13:22 2017 (r326964)
> > > @@ -38,6 +38,7 @@ __FBSDID("$FreeBSD$");
> > > #include <sys/malloc.h>
> > > #include <sys/kernel.h>
> > > #include <sys/bio.h>
> > > +#include <sys/conf.h>
> > > #include <sys/lock.h>
> > > #include <sys/mutex.h>
> > > #include <sys/buf.h>
> > > @@ -1158,7 +1159,7 @@ cam_periph_runccb(union ccb *ccb,
> > > struct bintime *starttime;
> > > struct bintime ltime;
> > > int error;
> > > - bool sched_stopped;
> > > + bool must_poll;
> > > struct mtx *periph_mtx;
> > > struct cam_periph *periph;
> > > uint32_t timeout = 1;
> > > @@ -1182,7 +1183,13 @@ cam_periph_runccb(union ccb *ccb,
> > > devstat_start_transaction(ds, starttime);
> > > }
> > >
> > > - sched_stopped = SCHEDULER_STOPPED();
> > > + /*
> > > + * We must poll the I/O while we're dumping. The scheduler is
> > normally
> > > + * stopped for dumping, except when we call doadump from ddb.
> > While the
> > > + * scheduler is running in this case, we still need to poll the
> > I/O to
> > > + * avoid sleeping waiting for the ccb to complete.
> > > + */
> > > + must_poll = dumping;
> >
> > Hmm, unfortunately this introduces a new problem: after a panic we call
> > adashutdown() as part of the shutdown_post_sync event. This occurs
> > before we call doadump(), so dumping == 0 and we don't poll for the
> > spindown command's completion. But since we've panicked, the scheduler
> > is stopped, and so we just hang.
> >
>
> So "dumping || SCHEDULER_STOPPED()" then is needed?
It seems so, unfortunately.
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