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Fix a couple of races with LWP park/unpark.

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This commit is contained in:
ad 2007-03-01 14:55:06 +00:00
parent e0c62458a2
commit 0bffc80584
2 changed files with 21 additions and 14 deletions
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32
sys/kern/sys_lwp.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: sys_lwp.c,v 1.7 2007/02/26 09:20:54 yamt Exp $ */
/* $NetBSD: sys_lwp.c,v 1.8 2007/03/01 14:55:06 ad Exp $ */
/*-
* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
@ -42,7 +42,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: sys_lwp.c,v 1.7 2007/02/26 09:20:54 yamt Exp $");
__KERNEL_RCSID(0, "$NetBSD: sys_lwp.c,v 1.8 2007/03/01 14:55:06 ad Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -73,6 +73,8 @@ struct evcnt lwp_ev_park_early = EVCNT_INITIALIZER(EVCNT_TYPE_MISC,
NULL, "_lwp_park", "unparked early");
struct evcnt lwp_ev_park_raced = EVCNT_INITIALIZER(EVCNT_TYPE_MISC,
NULL, "_lwp_park", "raced");
struct evcnt lwp_ev_park_slowpath = EVCNT_INITIALIZER(EVCNT_TYPE_MISC,
NULL, "_lwp_park", "slowpath");
struct evcnt lwp_ev_park_miss = EVCNT_INITIALIZER(EVCNT_TYPE_MISC,
NULL, "_lwp_park", "not parked");
struct evcnt lwp_ev_park_bcast = EVCNT_INITIALIZER(EVCNT_TYPE_MISC,
@ -93,6 +95,7 @@ lwp_sys_init(void)
sleeptab_init(&lwp_park_tab);
#ifdef LWP_COUNTERS
evcnt_attach_static(&lwp_ev_park_early);
evcnt_attach_static(&lwp_ev_park_slowpath);
evcnt_attach_static(&lwp_ev_park_raced);
evcnt_attach_static(&lwp_ev_park_miss);
evcnt_attach_static(&lwp_ev_park_bcast);
@ -150,7 +153,7 @@ sys__lwp_create(struct lwp *l, void *v, register_t *retval)
if (p->p_stat == SSTOP || (p->p_sflag & PS_STOPPING) != 0)
l2->l_stat = LSSTOP;
else {
LOCK_ASSERT(lwp_locked(l2, &sched_mutex));
KASSERT(lwp_locked(l2, &sched_mutex));
p->p_nrlwps++;
l2->l_stat = LSRUN;
setrunqueue(l2);
@ -483,14 +486,15 @@ sys__lwp_park(struct lwp *l, void *v, register_t *retval)
* Before going the full route and blocking, check to see if an
* unpark op is pending.
*/
if ((l->l_flag & LW_CANCELLED) != 0) {
sleepq_lwp_lock(l);
l->l_flag &= ~LW_CANCELLED;
sleepq_lwp_unlock(l);
lwp_lock(l);
if ((l->l_flag & (LW_CANCELLED | LW_UNPARKED)) != 0) {
l->l_flag &= ~(LW_CANCELLED | LW_UNPARKED);
lwp_unlock(l);
sleepq_unlock(sq);
LWP_COUNT(lwp_ev_park_early, 1);
return EALREADY;
}
lwp_unlock_to(l, sq->sq_mutex);
/*
* For now we ignore the ucontext argument. In the future, we may
@ -498,7 +502,7 @@ sys__lwp_park(struct lwp *l, void *v, register_t *retval)
* function could call sleepq_unblock() on our behalf.
*/
LWP_COUNT(lwp_ev_park, 1);
sleepq_enter(sq, l);
l->l_biglocks = 0; /* For sleepq_unblock() */
sleepq_block(sq, sched_kpri(l), wchan, "parked", timo, 1,
&lwp_park_sobj);
error = sleepq_unblock(timo, 1);
@ -538,6 +542,7 @@ sys__lwp_unpark(struct lwp *l, void *v, register_t *retval)
* The LWP hasn't parked yet. Take the hit
* and mark the operation as pending.
*/
LWP_COUNT(lwp_ev_park_slowpath, 1);
sleepq_unlock(sq);
mutex_enter(&p->p_smutex);
if ((t = lwp_find(p, target)) == NULL) {
@ -553,7 +558,7 @@ sys__lwp_unpark(struct lwp *l, void *v, register_t *retval)
* Wake it in the usual way.
*/
KASSERT(t->l_syncobj == &lwp_park_sobj);
LOCK_ASSERT(lwp_locked(t, sq->sq_mutex));
KASSERT(lwp_locked(t, sq->sq_mutex));
LWP_COUNT(lwp_ev_park_raced, 1);
} else {
/*
@ -561,17 +566,17 @@ sys__lwp_unpark(struct lwp *l, void *v, register_t *retval)
* on a different user sync object. The
* latter is an application error.
*/
t->l_flag |= LW_CANCELLED;
t->l_flag |= LW_UNPARKED;
lwp_unlock(t);
return 0;
}
}
swapin = sleepq_remove(sq, t);
LWP_COUNT(lwp_ev_park_targ, 1);
sleepq_unlock(sq);
if (swapin)
uvm_kick_scheduler();
LWP_COUNT(lwp_ev_park_targ, 1);
return 0;
}
@ -656,6 +661,7 @@ sys__lwp_unpark_all(struct lwp *l, void *v, register_t *retval)
* The LWP hasn't parked yet. Take the hit and
* mark the operation as pending.
*/
LWP_COUNT(lwp_ev_park_slowpath, 1);
sleepq_unlock(sq);
mutex_enter(&p->p_smutex);
if ((t = lwp_find(p, target)) == NULL) {
@ -672,7 +678,7 @@ sys__lwp_unpark_all(struct lwp *l, void *v, register_t *retval)
* Wake it in the usual way.
*/
KASSERT(t->l_syncobj == &lwp_park_sobj);
LOCK_ASSERT(lwp_locked(t, sq->sq_mutex));
KASSERT(lwp_locked(t, sq->sq_mutex));
LWP_COUNT(lwp_ev_park_raced, 1);
swapin |= sleepq_remove(sq, t);
unparked++;
@ -682,7 +688,7 @@ sys__lwp_unpark_all(struct lwp *l, void *v, register_t *retval)
* on a different user sync object. The
* latter is an application error.
*/
t->l_flag |= LW_CANCELLED;
t->l_flag |= LW_UNPARKED;
lwp_unlock(t);
sleepq_lock(sq);
}

3
sys/sys/lwp.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: lwp.h,v 1.54 2007/02/27 15:07:28 yamt Exp $ */
/* $NetBSD: lwp.h,v 1.55 2007/03/01 14:55:06 ad Exp $ */
/*-
* Copyright (c) 2001, 2006, 2007 The NetBSD Foundation, Inc.
@ -174,6 +174,7 @@ extern struct lwp lwp0; /* LWP for proc0 */
#define LW_PENDSIG 0x01000000 /* Pending signal for us */
#define LW_CANCELLED 0x02000000 /* tsleep should not sleep */
#define LW_WUSERRET 0x04000000 /* Call proc::p_userret on return to user */
#define LW_UNPARKED 0x01000000 /* unpark op pending */
#define LW_WREBOOT 0x08000000 /* System is rebooting, please suspend */
/* The second set of flags is kept in l_pflag. */