svn commit: r326964 - head/sys/cam

[Warner Losh]

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?

Warner