Skip site navigation (1)Skip section navigation (2)
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>

next in thread | previous in thread | raw e-mail | index | archive | help
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



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?BANLkTikmxbsCV_A-zD7XdkWyOEBzy67iZQ>