Date: Sun, 7 Jan 2001 21:11:59 -0600 From: Robert Lipe <robertlipe@usa.net> To: freebsd-hackers@FreeBSD.ORG Subject: kthread_exit & zombification Message-ID: <20010107211159.C1400@rjlhome.sco.com>
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Hi, Gang.
In 4.1.1, I have a pretty simple need for a kernel thread or two, but
I'm having problems with kthread_exit(). The problem is that the thread
goes zombie after I kthread_exit in it, but it never gets reaped. Since
I'm doing this during a MOD_UNLOAD phase, if I happen to do a `ps -ax'
after the module has been unmapped, a panic results becuase it's trying
to get the lwp name and wchan string from what is now unmapped memory.
But that's a secondary problem; the primary one is that I am missing
whatever it takes to get a ticket for the resulting kernel thread to go
to Byte Heaven.
After a couple of load/unload cycles, I see:
$ ps -alx | grep mem
0 357 0 2 0 0 0 0 - ZL ?? 0:00.00 (udi_memd)
0 360 0 2 0 0 0 0 - ZL ?? 0:00.00 (udi_memd)
0 920 0 2 0 0 0 0 - ZL ?? 0:00.00 (udi_memd)
0 954 0 0 0 0 0 0 udi_os SL ?? 0:00.00 (udi_memd)
The creation is pretty simple:
if (kthread_create(my_daemon, NULL,
&my_thread, "mydaemon")) {
printf("kthread_create failed!\n");
}
Once the interesting part is stripped away, the daemon itself is texbook:
_udi_alloc_daemon(void *arg)
{
while (!kill_daemon_req) {
/* do work */
}
wakeup(&_udi_kill_daemon);
kthread_exit(0);
}
And the code that does the teardown looks like:
case MOD_UNLOAD:
kill_daemon_req = TRUE;
/* poke the daemon to awaken it's 'work' loop */
...
tsleep(&_udi_kill_daemon, PZERO, "udiallocdeath", 0);
I can see the interlocks happening with the tsleep/wakeup, so I know
we're not unloading prematurely. There aren't many users of the kthread
facilities in the kernel and since they don't seem to be in modules, the
teardown case might have been skipped.
What am I missing?
Thanx,
RJL
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