svn commit: r328554 - head/sys/cam/scsi

[Warner Losh]

I think this is a good idea to MFC. We've had no reports of it causing
issues.

There's more extensive locking changes / tweaks needed for da that just
went in that likely should also be MFC'd.

Warner

On Sun, Mar 11, 2018 at 9:17 PM, Dexuan-BSD Cui <dexuan.bsd at gmail.com>
wrote:

> Hi imp and all,
> I think this patch is very important, because it can fix a panic I
> noticed recently when I try to hot-remove a SCSI disk from a VM
> running on Azure/Hyper-V.
>
> The panic is almost 100% reproducible with stable/11, but not in the
> latest CURRENT code, so finally I identified this fix in the CURRENT
> branch.
>
> Can you please MFC this patch to 11 and 10?
> It looks there is a major difference in the CAM code between 11/10
> and the CURRENT code, and we may have to MFC more related patches. If
> this is difficult, I hope at least we can provide a minimal re-written
> version of the patch to 11 and 10?
>
> Looking forward to your insight!
>
> Thanks,
> -- Dexuan
>
>
> On Mon, Jan 29, 2018 at 10:07 AM, Warner Losh <imp at freebsd.org> wrote:
> > Author: imp
> > Date: Mon Jan 29 18:07:14 2018
> > New Revision: 328554
> > URL: https://svnweb.freebsd.org/changeset/base/328554
> >
> > Log:
> >   Do the book-keeping on release before we release the reference. The
> >   periph was going away on final release, and then returning and we
> >   started dancing in free memory.
> >
> >   Sponsored by: Netflix
> >
> > Modified:
> >   head/sys/cam/scsi/scsi_da.c
> >
> > Modified: head/sys/cam/scsi/scsi_da.c
> > ============================================================
> ==================
> > --- head/sys/cam/scsi/scsi_da.c Mon Jan 29 17:32:30 2018        (r328553)
> > +++ head/sys/cam/scsi/scsi_da.c Mon Jan 29 18:07:14 2018        (r328554)
> > @@ -1549,12 +1549,12 @@ da_periph_unhold(struct cam_periph *periph,
> da_ref_tok
> >         struct da_softc *softc = periph->softc;
> >
> >         token_sanity(token);
> > -       cam_periph_unhold(periph);
> >         DA_PERIPH_PRINT(periph, "Unholding device %s (%d)\n",
> >             da_ref_text[token], token);
> >         cnt = atomic_fetchadd_int(&softc->ref_flags[token], -1);
> >         if (cnt != 1)
> >                 panic("Unholding %d with cnt = %d", token, cnt);
> > +       cam_periph_unhold(periph);
> >  }
> >
> >  static inline int
> > @@ -1583,12 +1583,12 @@ da_periph_release(struct cam_periph *periph,
> da_ref_to
> >         struct da_softc *softc = periph->softc;
> >
> >         token_sanity(token);
> > -       cam_periph_release(periph);
> >         DA_PERIPH_PRINT(periph, "releasing device %s (%d)\n",
> >             da_ref_text[token], token);
> >         cnt = atomic_fetchadd_int(&softc->ref_flags[token], -1);
> >         if (cnt != 1)
> >                 panic("Releasing %d with cnt = %d", token, cnt);
> > +       cam_periph_release(periph);
> >  }
> >
> >  static inline void
> > @@ -1598,12 +1598,12 @@ da_periph_release_locked(struct cam_periph
> *periph, da
> >         struct da_softc *softc = periph->softc;
> >
> >         token_sanity(token);
> > -       cam_periph_release_locked(periph);
> >         DA_PERIPH_PRINT(periph, "releasing device (locked) %s (%d)\n",
> >             da_ref_text[token], token);
> >         cnt = atomic_fetchadd_int(&softc->ref_flags[token], -1);
> >         if (cnt != 1)
> >                 panic("Unholding %d with cnt = %d", token, cnt);
> > +       cam_periph_release_locked(periph);
> >  }
> >
> >  #define cam_periph_hold POISON
> >
>