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From: Rui Lopes <rui@ruilopes.com>
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Date: 11 Aug 2003 13:10:24 +0100
Subject: Possible patch for vm/vm_glue.c
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Hello,

I've been reading vm_glue.c and I think I've found a bug regarding the
lock of `proc.p_sflag' inside `scheduler' function.

>From proc.h, "int p_sflag; /* (j) PS_* flags. */" and "(j) - locked by
sched_lock mtx";  but the access is done without having the lock.


Take a look at the attached patch and tell me if this is ok.

Patch made against "$FreeBSD: src/sys/vm/vm_glue.c,v 1.172 2003/05/13
20:36:02 jhb Exp $", but this is also present in current 1.182.


Regards,
Rui Lopes


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# we should only access `proc.p_sflag' when `sched_lock' is locked.
# From proc.h:
#    int             p_sflag;        /* (j) PS_* flags. */
# and j means: "(j) - locked by sched_lock mtx"
# -- Rui Lopes <rui@ruilopes.com>
--- vm_glue.c.orig	Mon Aug 11 12:41:33 2003
+++ vm_glue.c	Mon Aug 11 12:45:58 2003
@@ -596,10 +596,11 @@
 	sx_slock(&allproc_lock);
 	FOREACH_PROC_IN_SYSTEM(p) {
 		struct ksegrp *kg;
+		mtx_lock_spin(&sched_lock);
 		if (p->p_sflag & (PS_INMEM | PS_SWAPPINGOUT | PS_SWAPPINGIN)) {
+			mtx_unlock_spin(&sched_lock);
 			continue;
 		}
-		mtx_lock_spin(&sched_lock);
 		FOREACH_THREAD_IN_PROC(p, td) {
 			/*
 			 * An otherwise runnable thread of a process

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