cvs commit: src/sys/kern kern_sig.c

[Poul-Henning Kamp]

In message <200503031116.22840.jhb at FreeBSD.org>, John Baldwin writes:
>On Thursday 03 March 2005 10:21 am, Daniel Eischen wrote:
>> On Thu, 3 Mar 2005, Scott Long wrote:
>> > It's not about convenience or taking the easy way out.  Let's fix
>> > sigwait() to have the proper assumptions and go from there.  I'm
>> > inclined to agree with John that the problem is not widespread or
>> > impossible to track down.  Fixing it is not hard either, we already have
>> > the PHOLD()/PRELE() functions for doing exactly what is needed here.
>>
>> Can you add assertions in msleep(), cv_wait(), etc, to
>> panic if the object is on the kernel stack and the
>> stack is swappable?
>
>Just because you sleep on a stack address doesn't mean that you are going to 
>write to that object when doing a wakeup.  However, it might not be a bad 
>idea as stack address can be indicative of bugs like this:

In some cases the guaranteed anonymity of stack variables is actually a 
benefit.  See for instance the protective mutexes used #ifdef DIAGNOSTIC
in g_up(), g_down() and when calling callouts().

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.