svn commit: r326964 - head/sys/cam

Warner Losh imp at bsdimp.com
Wed Jan 10 20:38:43 UTC 2018


On Wed, Jan 10, 2018 at 1:35 PM, Mark Johnston <markj at freebsd.org> wrote:

> 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.
>

OK. Sounds good. I'll make the change today.


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