Date: Fri, 25 Oct 2002 16:00:46 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org Subject: Re: cvs commit: src/sys/kern kern_mutex.c Message-ID: <18323.1035554446@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 25 Oct 2002 09:50:53 EDT." <XFMail.20021025095053.jhb@FreeBSD.org>
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In message <XFMail.20021025095053.jhb@FreeBSD.org>, John Baldwin writes:
>
>On 25-Oct-2002 Poul-Henning Kamp wrote:
>> phk 2002/10/25 01:40:20 PDT
>>
>> Modified files:
>> sys/kern kern_mutex.c
>> Log:
>> Disable the kernacc() check in mtx_validate() until such time that kernacc
>> does not require Giant.
>>
>> This means that we may miss panics on a class of mutex programming bugs,
>> but only if running with a Chernobyl setting of debug-flags.
>>
>> Spotted by: Pete Carah <pete@ns.altadena.net>
>
>People probably should not be using MUTEX_DEBUG unless they are actually
>working on the mutex implementation anyways. We might even should just
>shoot that code in the head and put it out of its misery.
Maybe replace it by:
{
struct mtx tmp;
[...]
/* See if we can read/write the mutex */
bcopy(mp, &tmp, sizeof tmp);
bcopy(&tmp, mp, sizeof tmp);
If we want to retain some amount of checking.
Poul-Henning
PS: That reminds me, I've sometimes wondered if we should have a
global string pointer where one could leave a panic hint,
that could make the above code look something like:
{
struct mtx tmp;
[...]
/* See if we can read/write the mutex */
panic_hint("Mutex in wrong kind of RAM");
bcopy(mp, &tmp, sizeof tmp);
bcopy(&tmp, mp, sizeof tmp);
panic_hint(NULL);
And if explode on one of the bcopy() panic would leave a hint
about what the problem is:
panic(blablabla)
This may be why: Mutex in wrong kind of RAM.
Hint from: mtx_validate() line 886 in ../../../kern/kern_mutex.c
Just an idea...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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