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Move call to sched_unlock_idle to later in the context switch to 

eliminate a race where another processor could grab the outgoing
process before we were done saving our state into it, with predictable
results.

Bug spotted on i386 by Frank van der Linden <fvdl@wasabisystems.com>.
This commit is contained in:
thorpej 2002-04-30 16:05:13 +00:00
parent 9e14de40bb
commit d105d4c056
1 changed files with 13 additions and 10 deletions
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23
sys/arch/alpha/alpha/locore.s
View File

@ -1,4 +1,4 @@
/* $NetBSD: locore.s,v 1.98 2001/08/29 20:17:08 nathanw Exp $ */
/* $NetBSD: locore.s,v 1.99 2002/04/30 16:05:13 thorpej Exp $ */
/*-
* Copyright (c) 1999, 2000 The NetBSD Foundation, Inc.
@ -73,7 +73,7 @@
#include <machine/asm.h>
__KERNEL_RCSID(0, "$NetBSD: locore.s,v 1.98 2001/08/29 20:17:08 nathanw Exp $");
__KERNEL_RCSID(0, "$NetBSD: locore.s,v 1.99 2002/04/30 16:05:13 thorpej Exp $");
#include "assym.h"
@ -828,13 +828,6 @@ cpu_switch_queuescan:
5:
mov t4, s2 /* save new proc */
ldq s3, P_MD_PCBPADDR(s2) /* save new pcbpaddr */
#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
/*
* Done mucking with the run queues, release the
* scheduler lock, but keep interrupts out.
*/
CALL(sched_unlock_idle)
#endif
/*
* Check to see if we're switching to ourself. If we are,
@ -879,7 +872,17 @@ cpu_switch_queuescan:
mov s3, a0 /* swap the context */
SWITCH_CONTEXT
7: /*
7:
#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
/*
* Done mucking with the run queues, and we have fully switched
* to the new process. Release the scheduler lock, but keep
* interrupts out.
*/
CALL(sched_unlock_idle)
#endif
/*
* Now that the switch is done, update curproc and other
* globals. We must do this even if switching to ourselves
* because we might have re-entered cpu_switch() from idle(),