[src/trunk]: src/sys/fs/union Use mutexes to protect the hash lists instead o...

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b22639b21e07
branches:  trunk
changeset: 768257:b22639b21e07
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sat Aug 13 10:48:14 2011 +0000

description:
Use mutexes to protect the hash lists instead of tsleep/wakeup.

diffstat:

 sys/fs/union/union_subr.c |  78 ++++++++++++++--------------------------------
 1 files changed, 24 insertions(+), 54 deletions(-)

diffs (205 lines):

diff -r e04a1f6fc81b -r b22639b21e07 sys/fs/union/union_subr.c
--- a/sys/fs/union/union_subr.c Sat Aug 13 10:33:52 2011 +0000
+++ b/sys/fs/union/union_subr.c Sat Aug 13 10:48:14 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: union_subr.c,v 1.48 2011/08/12 17:41:17 hannken Exp $  */
+/*     $NetBSD: union_subr.c,v 1.49 2011/08/13 10:48:14 hannken Exp $  */
 
 /*
  * Copyright (c) 1994
@@ -72,7 +72,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.48 2011/08/12 17:41:17 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: union_subr.c,v 1.49 2011/08/13 10:48:14 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -103,10 +103,8 @@
        (((((unsigned long) (u)) + ((unsigned long) l)) >> 8) & (NHASH-1))
 
 static LIST_HEAD(unhead, union_node) unhead[NHASH];
-static int unvplock[NHASH];
+static kmutex_t unheadlock[NHASH];
 
-static int union_list_lock(int);
-static void union_list_unlock(int);
 void union_updatevp(struct union_node *, struct vnode *, struct vnode *);
 static int union_relookup(struct union_mount *, struct vnode *,
                               struct vnode **, struct componentname *,
@@ -121,9 +119,10 @@
 {
        int i;
 
-       for (i = 0; i < NHASH; i++)
+       for (i = 0; i < NHASH; i++) {
                LIST_INIT(&unhead[i]);
-       memset(unvplock, 0, sizeof(unvplock));
+               mutex_init(&unheadlock[i], MUTEX_DEFAULT, IPL_NONE);
+       }
 }
 
 /*
@@ -132,38 +131,15 @@
 void
 union_done(void)
 {
+       int i;
+
+       for (i = 0; i < NHASH; i++)
+               mutex_destroy(&unheadlock[i]);
 
        /* Make sure to unset the readdir hook. */
        vn_union_readdir_hook = NULL;
 }
 
-static int
-union_list_lock(int ix)
-{
-
-       if (unvplock[ix] & UN_LOCKED) {
-               unvplock[ix] |= UN_WANTED;
-               (void) tsleep(&unvplock[ix], PINOD, "unionlk", 0);
-               return (1);
-       }
-
-       unvplock[ix] |= UN_LOCKED;
-
-       return (0);
-}
-
-static void
-union_list_unlock(int ix)
-{
-
-       unvplock[ix] &= ~UN_LOCKED;
-
-       if (unvplock[ix] & UN_WANTED) {
-               unvplock[ix] &= ~UN_WANTED;
-               wakeup(&unvplock[ix]);
-       }
-}
-
 void
 union_updatevp(struct union_node *un, struct vnode *uppervp,
        struct vnode *lowervp)
@@ -186,11 +162,9 @@
        }
 
        if (lhash != uhash)
-               while (union_list_lock(lhash))
-                       continue;
+               mutex_enter(&unheadlock[lhash]);
 
-       while (union_list_lock(uhash))
-               continue;
+       mutex_enter(&unheadlock[uhash]);
 
        if (ohash != nhash || !docache) {
                if (un->un_flags & UN_CACHED) {
@@ -200,7 +174,7 @@
        }
 
        if (ohash != nhash)
-               union_list_unlock(ohash);
+               mutex_exit(&unheadlock[ohash]);
 
        if (un->un_lowervp != lowervp) {
                if (un->un_lowervp) {
@@ -237,7 +211,7 @@
                un->un_flags |= UN_CACHED;
        }
 
-       union_list_unlock(nhash);
+       mutex_exit(&unheadlock[nhash]);
 }
 
 void
@@ -394,8 +368,7 @@
                        break;
                }
 
-               while (union_list_lock(hash))
-                       continue;
+               mutex_enter(&unheadlock[hash]);
 
                for (un = unhead[hash].lh_first; un != 0;
                                        un = un->un_cache.le_next) {
@@ -407,14 +380,14 @@
                                vp = UNIONTOV(un);
                                mutex_enter(vp->v_interlock);
                                if (vget(vp, 0)) {
-                                       union_list_unlock(hash);
+                                       mutex_exit(&unheadlock[hash]);
                                        goto loop;
                                }
                                break;
                        }
                }
 
-               union_list_unlock(hash);
+               mutex_exit(&unheadlock[hash]);
 
                if (un)
                        break;
@@ -528,8 +501,7 @@
        }
 
        if (docache) {
-               while (union_list_lock(hash))
-                       continue;
+               mutex_enter(&unheadlock[hash]);
                LIST_FOREACH(un1, &unhead[hash], un_cache) {
                        if (un1->un_lowervp == lowervp &&
                            un1->un_uppervp == uppervp &&
@@ -538,7 +510,7 @@
                                 * Another thread beat us, push back freshly
                                 * allocated vnode and retry.
                                 */
-                               union_list_unlock(hash);
+                               mutex_exit(&unheadlock[hash]);
                                ungetnewvnode(*vpp);
                                goto loop;
                        }
@@ -603,7 +575,7 @@
 
 out:
        if (docache)
-               union_list_unlock(hash);
+               mutex_exit(&unheadlock[hash]);
 
        return (error);
 }
@@ -616,13 +588,12 @@
 
        hash = UNION_HASH(un->un_uppervp, un->un_lowervp);
 
-       while (union_list_lock(hash))
-               continue;
+       mutex_enter(&unheadlock[hash]);
        if (un->un_flags & UN_CACHED) {
                un->un_flags &= ~UN_CACHED;
                LIST_REMOVE(un, un_cache);
        }
-       union_list_unlock(hash);
+       mutex_exit(&unheadlock[hash]);
 
        if (un->un_pvp != NULLVP)
                vrele(un->un_pvp);
@@ -1060,13 +1031,12 @@
 
        hash = UNION_HASH(un->un_uppervp, un->un_lowervp);
 
-       while (union_list_lock(hash))
-               continue;
+       mutex_enter(&unheadlock[hash]);
        if (un->un_flags & UN_CACHED) {
                un->un_flags &= ~UN_CACHED;
                LIST_REMOVE(un, un_cache);
        }
-       union_list_unlock(hash);
+       mutex_exit(&unheadlock[hash]);
 
        if (un->un_flags & UN_ULOCK) {
                un->un_flags &= ~UN_ULOCK;