Date: Wed, 18 May 2011 13:43:43 -0700 From: mdf@FreeBSD.org To: Attilio Rao <attilio@freebsd.org> Cc: src-committers@freebsd.org, Pawel Jakub Dawidek <pjd@freebsd.org>, Andriy Gapon <avg@freebsd.org>, svn-src-user@freebsd.org Subject: Re: svn commit: r222060 - in user/avg/xcpu/sys: kern sys Message-ID: <BANLkTikmxbsCV_A-zD7XdkWyOEBzy67iZQ@mail.gmail.com> In-Reply-To: <BANLkTikAnB-3XbvDwGHgyqyJquH9BhqzOQ@mail.gmail.com> References: <201105181508.p4IF8UoS096841@svn.freebsd.org> <20110518182441.GB2273@garage.freebsd.pl> <4DD4243C.4070301@FreeBSD.org> <BANLkTikAnB-3XbvDwGHgyqyJquH9BhqzOQ@mail.gmail.com>
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On Wed, May 18, 2011 at 1:06 PM, Attilio Rao <attilio@freebsd.org> wrote: > 2011/5/18 Andriy Gapon <avg@freebsd.org>: >> on 18/05/2011 21:24 Pawel Jakub Dawidek said the following: >>> On Wed, May 18, 2011 at 03:08:30PM +0000, Andriy Gapon wrote: >>> [...] >>>> --- user/avg/xcpu/sys/sys/proc.h =A0 =A0 Wed May 18 15:07:36 2011 =A0 = =A0 =A0 =A0(r222059) >>>> +++ user/avg/xcpu/sys/sys/proc.h =A0 =A0 Wed May 18 15:08:30 2011 =A0 = =A0 =A0 =A0(r222060) >>>> @@ -781,7 +781,7 @@ MALLOC_DECLARE(M_SUBPROC); >>>> =A0 * Otherwise, the kernel will deadlock since the scheduler isn't >>>> =A0 * going to run the thread that holds the lock we need. >>>> =A0 */ >>>> -#define =A0 =A0 THREAD_PANICED() =A0 =A0 =A0 =A0\ >>>> +#define =A0 =A0 TD_IS_INPANIC() \ >>>> =A0 =A0 =A0(panicstr !=3D NULL && (curthread->td_flags & TDF_INPANIC) = !=3D 0) >>> >>> Does TDF_INPANIC make sense without panicstr being set? >> >> Very good observation. =A0It seems that TDF_INPANIC can never be set unl= ess >> panicstr is set. =A0So, I guess it should be OK to simplify the macro fu= rther. >> Thank you. > > However I think that TDF_INPANIC handling is not optimal. > You should really acquire thread_lock otherwise you are going to break > choosethread() concurrency. > > I would prefer to make TDF_INPANIC a private flag and just use it with > curthread, if possible, but I still don't have a good way to resolve > choosethread() (I would dig the runqueue adding path and resolve the > problem later in the codeflow, I think). I know it's almost required now (sync on reboot?!?!), but I would strongly question, from an architectural standpoint, why the scheduler should be running at all in panic. Once a thread pulls the panic trigger, nothing else should run except ddb in that thread's context. Cheers, matthew
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