Date: Fri, 26 Oct 2007 14:20:33 -0400 From: John Baldwin <jhb@freebsd.org> To: Julian Elischer <julian@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/sys kthread.h src/sys/kern kern_kthread.c Message-ID: <200710261420.34168.jhb@freebsd.org> In-Reply-To: <200710261703.l9QH3Nmt061137@repoman.freebsd.org> References: <200710261703.l9QH3Nmt061137@repoman.freebsd.org>
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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);
...
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.?
--
John Baldwin
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