Date: Mon, 12 Mar 2018 10:44:44 -0600 From: Warner Losh <imp@bsdimp.com> To: Dexuan-BSD Cui <dexuan.bsd@gmail.com> Cc: Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org, Dexuan Cui <decui@microsoft.com> Subject: Re: svn commit: r328554 - head/sys/cam/scsi Message-ID: <CANCZdfoS4tp2JXyHdNuNyMx0Juqg37MUGb3LfV5dFomin=JTXg@mail.gmail.com> In-Reply-To: <CABkgQk_QXs7yoTbUe=ZCTyyVLoo_-_0aGHU_q8RfimiMmLoO1Q@mail.gmail.com> References: <201801291807.w0TI7EVD092154@repo.freebsd.org> <CABkgQk_QXs7yoTbUe=ZCTyyVLoo_-_0aGHU_q8RfimiMmLoO1Q@mail.gmail.com>
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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@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@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 > > >
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