Date: Wed, 24 Apr 2013 00:47:22 +0400 From: Gleb Smirnoff <glebius@FreeBSD.org> To: current@FreeBSD.org Subject: Re: panic on a NULL turnstile on boot on r249810 Message-ID: <20130423204722.GM76816@FreeBSD.org> In-Reply-To: <20130423202502.GL76816@glebius.int.ru> References: <20130423202502.GL76816@glebius.int.ru>
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More investigation. AFAIU, we can't come to this point
if __mtx_lock_sleep() passed a NULL ts. So ts wasn't NULL
before call to propagate_priority(). The turnstile_wait()
saves ts on td:
738: td->td_blocked = ts;
So I can obtain it:
(kgdb) fr 11
#11 0xffffffff805206b2 in turnstile_wait (ts=<value optimized out>,
owner=<value optimized out>, queue=<value optimized out>)
at /usr/src/head/sys/kern/subr_turnstile.c:743
743 propagate_priority(td);
(kgdb) p *td->td_blocked
$8 = {ts_lock = {lock_object = {lo_name = 0xffffffff8077f1eb "turnstile lock",
lo_flags = 720896, lo_data = 0, lo_witness = 0x0},
mtx_lock = 18446741874883377440}, ts_blocked = {{
tqh_first = 0xfffffe000bbf3920, tqh_last = 0xfffffe000bbf3960}, {
tqh_first = 0x0, tqh_last = 0xfffffe000ba82ab0}}, ts_pending = {
tqh_first = 0x0, tqh_last = 0xfffffe000ba82ac0}, ts_hash = {le_next = 0x0,
le_prev = 0xffffffff80aaee38}, ts_link = {le_next = 0x0,
le_prev = 0xfffffe000bf42120}, ts_free = {lh_first = 0x0},
ts_lockobj = 0xffffffff80af5f30, ts_owner = 0xfffffe000bf42000}
(kgdb)
Ok, let's see who is the owner:
(kgdb) p td->td_blocked->ts_owner->td_proc->p_comm
$21 = "sysctl", '\0' <repeats 13 times>
I can't find it in info threads... Yep, it is zombie:
(kgdb) p td->td_blocked->ts_owner->td_proc->p_state
$22 = PRS_ZOMBIE
Could that happen that a zombie owns turnstile?
--
Totus tuus, Glebius.
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