Date: Fri, 26 Oct 2007 12:01:50 -0700 From: Julian Elischer <julian@elischer.org> To: John Baldwin <jhb@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Julian Elischer <julian@freebsd.org>, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/sys kthread.h src/sys/kern kern_kthread.c Message-ID: <4722399E.3090209@elischer.org> In-Reply-To: <200710261420.34168.jhb@freebsd.org> References: <200710261703.l9QH3Nmt061137@repoman.freebsd.org> <200710261420.34168.jhb@freebsd.org>
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John Baldwin wrote:
> On Friday 26 October 2007 01:03:22 pm Julian Elischer wrote:
>> julian 2007-10-26 17:03:22 UTC
>>
>> FreeBSD src repository
>>
>> Modified files:
>> sys/sys kthread.h
>> sys/kern kern_kthread.c
>> Log:
>> kthread_exit needs no stinkin argument.
>
> So an important property of the old kthread_exit() (now kproc_exit()) was that
> a kernel module could safely ensure that a kthread it created was out of the
> kernel module's text segment before returning from a module unload hook to
> prevent kernel panics by sleeping on the proc pointer with the proc lock like
> so:
>
> mtx_lock(&mylock);
> PROC_LOCK(p);
> signal_death = 1;
> mtx_unlock(&mylock);
> msleep(p, &p->p_mtx, ...);
> PROC_UNLOCK(p);
>
> And have the main thread do this:
>
> ...
> mtx_lock(&mylock);
> while (!signal_death) {
> ... fetch work, may drop mylock...
> }
> mtx_unlock(&mylock);
> kthread_exit(0);
the kproc_exit still does..
I didn't see any users of it in the code that I've switched to kthreads
so far so I haven't added it to the kthread_exit() yet.
the intr code does:
thread_lock(td);
ithread->it_flags |= IT_DEAD;
if (TD_AWAITING_INTR(td)) {
TD_CLR_IWAIT(td);
sched_add(td, SRQ_INTR);
}
thread_unlock(td);
but no wait.
but I'll look further.. maybe it's in the drivers?
> ...
>
> That was the purpose of the 'wakeup(curthread->td_proc)' in the old
> kthread_exit(). How is this race handled now since the new kthread_exit()
> doesn't have any wakeups, etc.?
>
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