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cache_enter: inline LIST_INSERT_HEAD so that the membar_producer() can be 

put in the right spot. The 'next' link in the new entry must become globally
visible before the list head is updated. This could have affected systems
with weak memory ordering like the alpha.
This commit is contained in:
ad 2008-04-12 17:34:26 +00:00
parent da60beabf5
commit a78ad62cfb
1 changed files with 8 additions and 3 deletions
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11
sys/kern/vfs_cache.c
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@ -1,4 +1,4 @@
/* $NetBSD: vfs_cache.c,v 1.73 2008/04/11 15:25:24 ad Exp $ */
/* $NetBSD: vfs_cache.c,v 1.74 2008/04/12 17:34:26 ad Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@ -65,7 +65,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.73 2008/04/11 15:25:24 ad Exp $");
__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.74 2008/04/12 17:34:26 ad Exp $");
#include "opt_ddb.h"
#include "opt_revcache.h"
@ -597,9 +597,14 @@ cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
* Flush updates before making visible in table. No need for a
* memory barrier on the other side: to see modifications the
* list must be followed, meaning a dependent pointer load.
* The below is LIST_INSERT_HEAD() inlined, with the memory
* barrier included in the correct place.
*/
if ((ncp->nc_hash.le_next = ncpp->lh_first) != NULL)
ncpp->lh_first->nc_hash.le_prev = &ncp->nc_hash.le_next;
ncp->nc_hash.le_prev = &ncpp->lh_first;
membar_producer();
LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
ncpp->lh_first = ncp;
ncp->nc_vhash.le_prev = NULL;
ncp->nc_vhash.le_next = NULL;