Module Name: src
Committed By: christos
Date: Wed Dec 3 01:30:32 UTC 2014
Modified Files:
src/sys/kern: vfs_cache.c
Log Message:
Reverts previous: Causes all processes to hang in tstile in rw_lock from
genfs_lock during a make -j 20 build
To generate a diff of this commit:
cvs rdiff -u -r1.100 -r1.101 src/sys/kern/vfs_cache.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_cache.c
diff -u src/sys/kern/vfs_cache.c:1.100 src/sys/kern/vfs_cache.c:1.101
--- src/sys/kern/vfs_cache.c:1.100 Sat Nov 29 23:11:03 2014
+++ src/sys/kern/vfs_cache.c Tue Dec 2 20:30:32 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_cache.c,v 1.100 2014/11/30 04:11:03 dennis Exp $ */
+/* $NetBSD: vfs_cache.c,v 1.101 2014/12/03 01:30:32 christos Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.100 2014/11/30 04:11:03 dennis Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.101 2014/12/03 01:30:32 christos Exp $");
#include "opt_ddb.h"
#include "opt_revcache.h"
@@ -102,39 +102,7 @@ __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,
*/
/*
- * The locking in this subsystem works as follows:
- *
- * When an entry is added to the cache, via cache_enter(),
- * namecache_lock is taken to exclude other writers. The new
- * entry is added to the hash list in a way which permits
- * concurrent lookups and invalidations in the cache done on
- * other CPUs to continue in parallel.
- *
- * When a lookup is done in the cache, via cache_lookup() or
- * cache_lookup_raw(), the per-cpu lock below is taken. This
- * protects calls to cache_lookup_entry() and cache_invalidate()
- * against cache_reclaim(), and protects the per-cpu stats against
- * modification in both cache_reclaim() and cache_stat_sysctl(),
- * but allows lookups to continue in parallel with cache_enter().
- *
- * cache_revlookup() takes namecache_lock to exclude cache_enter()
- * and cache_reclaim() since the list it operates on is not
- * maintained to allow concurrent reads.
- *
- * When cache_reclaim() is called namecache_lock is held to hold
- * off calls to cache_enter() and each of the per-cpu locks is
- * taken to hold off lookups. Holding all these locks essentially
- * idles the subsystem, ensuring there are no concurrent references
- * to the cache entries being freed. As a side effect, once the
- * per-cpu locks are held, the per-cpu stats are added to the
- * subsystem totals and then zeroed. cache_stat_sysctl() similarly
- * takes all locks to collect the per-cpu stats (though it perhaps
- * could avoid this by living with stats that were a second out
- * of date?).
- *
- * The per-cpu namecache data is defined below. cpu_lock is used
- * to protect cpu_stats updates and to exclude cache_reclaim()
- * during lookups.
+ * Per-cpu namecache data.
*/
struct nchcpu {
kmutex_t cpu_lock;
@@ -219,8 +187,6 @@ cache_hash(const char *name, size_t name
/*
* Invalidate a cache entry and enqueue it for garbage collection.
- * The caller needs to hold namecache_lock or a per-cpu lock to hold
- * off cache_reclaim().
*/
static void
cache_invalidate(struct namecache *ncp)
@@ -321,8 +287,6 @@ cache_unlock_cpus(void)
/*
* Find a single cache entry and return it locked.
- * The caller needs to hold namecache_lock or a per-cpu lock to hold
- * off cache_reclaim().
*/
static struct namecache *
cache_lookup_entry(const struct vnode *dvp, const char *name, size_t namelen)
@@ -332,11 +296,11 @@ cache_lookup_entry(const struct vnode *d
nchash_t hash;
KASSERT(dvp != NULL);
+ KASSERT(mutex_owned(namecache_lock));
hash = cache_hash(name, namelen);
ncpp = &nchashtbl[NCHASH2(hash, dvp)];
LIST_FOREACH(ncp, ncpp, nc_hash) {
- /* XXX Needs barrier for Alpha here */
if (ncp->nc_dvp != dvp ||
ncp->nc_nlen != namelen ||
memcmp(ncp->nc_name, name, (u_int)ncp->nc_nlen))
@@ -411,8 +375,7 @@ cache_lookup(struct vnode *dvp, const ch
struct namecache *ncp;
struct vnode *vp;
struct nchcpu *cpup;
- int error, ret_value;
-
+ int error;
/* Establish default result values */
if (iswht_ret != NULL) {
@@ -425,23 +388,27 @@ cache_lookup(struct vnode *dvp, const ch
}
cpup = curcpu()->ci_data.cpu_nch;
- mutex_enter(&cpup->cpu_lock);
if (__predict_false(namelen > NCHNAMLEN)) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_long);
mutex_exit(&cpup->cpu_lock);
/* found nothing */
return 0;
}
-
+ mutex_enter(namecache_lock);
ncp = cache_lookup_entry(dvp, name, namelen);
+ mutex_exit(namecache_lock);
if (__predict_false(ncp == NULL)) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_miss);
mutex_exit(&cpup->cpu_lock);
/* found nothing */
return 0;
}
if ((cnflags & MAKEENTRY) == 0) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_badhits);
+ mutex_exit(&cpup->cpu_lock);
/*
* Last component and we are renaming or deleting,
* the cache entry is invalid, or otherwise don't
@@ -449,7 +416,6 @@ cache_lookup(struct vnode *dvp, const ch
*/
cache_invalidate(ncp);
mutex_exit(&ncp->nc_lock);
- mutex_exit(&cpup->cpu_lock);
/* found nothing */
return 0;
}
@@ -466,11 +432,16 @@ cache_lookup(struct vnode *dvp, const ch
if (__predict_true(nameiop != CREATE ||
(cnflags & ISLASTCN) == 0)) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_neghits);
+ mutex_exit(&cpup->cpu_lock);
+ mutex_exit(&ncp->nc_lock);
/* found neg entry; vn is already null from above */
- ret_value = 1;
+ return 1;
} else {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_badhits);
+ mutex_exit(&cpup->cpu_lock);
/*
* Last component and we are renaming or
* deleting, the cache entry is invalid,
@@ -478,49 +449,47 @@ cache_lookup(struct vnode *dvp, const ch
* exist.
*/
cache_invalidate(ncp);
+ mutex_exit(&ncp->nc_lock);
/* found nothing */
- ret_value = 0;
+ return 0;
}
- mutex_exit(&ncp->nc_lock);
- mutex_exit(&cpup->cpu_lock);
- return ret_value;
}
vp = ncp->nc_vp;
mutex_enter(vp->v_interlock);
mutex_exit(&ncp->nc_lock);
-
- /*
- * Drop per-cpu lock across the call to vget(), take it
- * again for the sake of the stats update.
- */
- mutex_exit(&cpup->cpu_lock);
error = vget(vp, LK_NOWAIT);
- mutex_enter(&cpup->cpu_lock);
if (error) {
KASSERT(error == EBUSY);
/*
* This vnode is being cleaned out.
* XXX badhits?
*/
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_falsehits);
+ mutex_exit(&cpup->cpu_lock);
/* found nothing */
- ret_value = 0;
- } else {
- COUNT(cpup->cpu_stats, ncs_goodhits);
- /* found it */
- *vn_ret = vp;
- ret_value = 1;
+ return 0;
}
+
+#ifdef DEBUG
+ /*
+ * since we released nb->nb_lock,
+ * we can't use this pointer any more.
+ */
+ ncp = NULL;
+#endif /* DEBUG */
+
+ /* We don't have the right lock, but this is only for stats. */
+ mutex_enter(&cpup->cpu_lock);
+ COUNT(cpup->cpu_stats, ncs_goodhits);
mutex_exit(&cpup->cpu_lock);
- return ret_value;
+ /* found it */
+ *vn_ret = vp;
+ return 1;
}
-
-/*
- * Cut-'n-pasted version of the above without the nameiop argument.
- */
int
cache_lookup_raw(struct vnode *dvp, const char *name, size_t namelen,
uint32_t cnflags,
@@ -529,7 +498,7 @@ cache_lookup_raw(struct vnode *dvp, cons
struct namecache *ncp;
struct vnode *vp;
struct nchcpu *cpup;
- int error, ret_value;
+ int error;
/* Establish default results. */
if (iswht_ret != NULL) {
@@ -543,15 +512,18 @@ cache_lookup_raw(struct vnode *dvp, cons
}
cpup = curcpu()->ci_data.cpu_nch;
- mutex_enter(&cpup->cpu_lock);
if (__predict_false(namelen > NCHNAMLEN)) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_long);
mutex_exit(&cpup->cpu_lock);
/* found nothing */
return 0;
}
+ mutex_enter(namecache_lock);
ncp = cache_lookup_entry(dvp, name, namelen);
+ mutex_exit(namecache_lock);
if (__predict_false(ncp == NULL)) {
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_miss);
mutex_exit(&cpup->cpu_lock);
/* found nothing */
@@ -567,40 +539,37 @@ cache_lookup_raw(struct vnode *dvp, cons
/*cnp->cn_flags |= ncp->nc_flags;*/
*iswht_ret = (ncp->nc_flags & ISWHITEOUT) != 0;
}
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_neghits);
- mutex_exit(&ncp->nc_lock);
mutex_exit(&cpup->cpu_lock);
+ mutex_exit(&ncp->nc_lock);
/* found negative entry; vn is already null from above */
return 1;
}
mutex_enter(vp->v_interlock);
mutex_exit(&ncp->nc_lock);
-
- /*
- * Drop per-cpu lock across the call to vget(), take it
- * again for the sake of the stats update.
- */
- mutex_exit(&cpup->cpu_lock);
error = vget(vp, LK_NOWAIT);
- mutex_enter(&cpup->cpu_lock);
if (error) {
KASSERT(error == EBUSY);
/*
* This vnode is being cleaned out.
* XXX badhits?
*/
+ mutex_enter(&cpup->cpu_lock);
COUNT(cpup->cpu_stats, ncs_falsehits);
+ mutex_exit(&cpup->cpu_lock);
/* found nothing */
- ret_value = 0;
- } else {
- COUNT(cpup->cpu_stats, ncs_goodhits); /* XXX can be "badhits" */
- /* found it */
- *vn_ret = vp;
- ret_value = 1;
+ return 0;
}
+
+ /* Unlocked, but only for stats. */
+ mutex_enter(&cpup->cpu_lock);
+ COUNT(cpup->cpu_stats, ncs_goodhits); /* XXX can be "badhits" */
mutex_exit(&cpup->cpu_lock);
- return ret_value;
+ /* found it */
+ *vn_ret = vp;
+ return 1;
}
/*
