Date: Wed, 10 Jan 2018 16:15:53 -0700 From: Warner Losh <imp@bsdimp.com> To: Mark Johnston <markj@freebsd.org> Cc: Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r326964 - head/sys/cam Message-ID: <CANCZdfpyVrLG-phSfKH4SuHhAywaQDFBK6jQCcQJK4y-QOs7Eg@mail.gmail.com> In-Reply-To: <CANCZdfpow8Hkau0FRycN=YvYN3XNQ%2BGEivoeA%2B=4CysrS95PYw@mail.gmail.com> References: <201712190413.vBJ4DMY9090982@repo.freebsd.org> <20180110202442.GC78524@raichu> <CANCZdfrNfkqkSTC7gsm-0dMstQYH1vayJEnx8hW297Cn6OiP4g@mail.gmail.com> <20180110203515.GD78524@raichu> <CANCZdfpow8Hkau0FRycN=YvYN3XNQ%2BGEivoeA%2B=4CysrS95PYw@mail.gmail.com>
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On Wed, Jan 10, 2018 at 1:38 PM, Warner Losh <imp@bsdimp.com> wrote: > > > On Wed, Jan 10, 2018 at 1:35 PM, Mark Johnston <markj@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@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. > https://reviews.freebsd.org/D13845 is up, if anybody wants to take a look. Warner
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