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Since sadata_upcall_alloc(1) can sleep, call it before checking the 

supply of stacks, to avoid a race. Problem pointed out by Lars
Heidieker on current-users.
This commit is contained in:
nathanw 2003-02-10 19:02:52 +00:00
parent 504b72aeba
commit 695bc028ab
1 changed files with 9 additions and 9 deletions
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18
sys/kern/kern_sa.c
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@ -1,4 +1,4 @@
/* $NetBSD: kern_sa.c,v 1.7 2003/02/05 15:38:14 briggs Exp $ */
/* $NetBSD: kern_sa.c,v 1.8 2003/02/10 19:02:52 nathanw Exp $ */
/*-
* Copyright (c) 2001 The NetBSD Foundation, Inc.
@ -37,7 +37,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_sa.c,v 1.7 2003/02/05 15:38:14 briggs Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_sa.c,v 1.8 2003/02/10 19:02:52 nathanw Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -769,6 +769,10 @@ sa_upcall_userret(struct lwp *l)
DPRINTFN(8,("sa_upcall_userret(%d.%d) unblocking\n",
p->p_pid, l->l_lid));
l->l_flag &= ~L_SA;
sau = sadata_upcall_alloc(1);
l->l_flag |= L_SA;
while (sa->sa_nstacks == 0) {
/*
* This should be a transient condition, so we'll just
@ -781,9 +785,9 @@ sa_upcall_userret(struct lwp *l)
* LWP that was running before we were woken up from
* the sleep that invoked the UNBLOCKED upcall.
* If it was a running one, it is on the runqueue
* and it will get to run again when the system
* gets to it, just not this second. If it's idle,
* it will remain idle, because we don't touch it.
* and it will run again when the system gets to it,
* just not this second. If it's idle, it will
* remain idle, because we don't touch it.
*
* Ideally, tsleep() would have a variant that took
* a LWP to switch to.
@ -799,10 +803,6 @@ sa_upcall_userret(struct lwp *l)
}
l2 = sa_vp_repossess(l);
l->l_flag &= ~L_SA;
sau = sadata_upcall_alloc(1);
l->l_flag |= L_SA;
KDASSERT(sa->sa_nstacks > 0);
st = sa->sa_stacks[--sa->sa_nstacks];