Author: kib
Date: Sun Jun 22 08:30:43 2014
New Revision: 267713
URL: http://svnweb.freebsd.org/changeset/base/267713
Log:
MFC r267255:
Change the nblock mutex to rwlock.
MFC r267264:
Devolatile as needed.
Modified:
stable/10/sys/kern/vfs_bio.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/kern/vfs_bio.c
==============================================================================
--- stable/10/sys/kern/vfs_bio.c Sun Jun 22 06:54:36 2014
(r267712)
+++ stable/10/sys/kern/vfs_bio.c Sun Jun 22 08:30:43 2014
(r267713)
@@ -251,7 +251,7 @@ static struct mtx_padalign rbreqlock;
/*
* Lock that protects needsbuffer and the sleeps/wakeups surrounding it.
*/
-static struct mtx_padalign nblock;
+static struct rwlock_padalign nblock;
/*
* Lock that protects bdirtywait.
@@ -296,7 +296,7 @@ static int runningbufreq;
* Used in numdirtywakeup(), bufspacewakeup(), bufcountadd(), bwillwrite(),
* getnewbuf(), and getblk().
*/
-static int needsbuffer;
+static volatile int needsbuffer;
/*
* Synchronization for bwillwrite() waiters.
@@ -426,18 +426,27 @@ bdirtyadd(void)
static __inline void
bufspacewakeup(void)
{
+ int need_wakeup, on;
/*
* If someone is waiting for BUF space, wake them up. Even
* though we haven't freed the kva space yet, the waiting
* process will be able to now.
*/
- mtx_lock(&nblock);
- if (needsbuffer & VFS_BIO_NEED_BUFSPACE) {
- needsbuffer &= ~VFS_BIO_NEED_BUFSPACE;
- wakeup(&needsbuffer);
+ rw_rlock(&nblock);
+ for (;;) {
+ need_wakeup = 0;
+ on = needsbuffer;
+ if ((on & VFS_BIO_NEED_BUFSPACE) == 0)
+ break;
+ need_wakeup = 1;
+ if (atomic_cmpset_rel_int(&needsbuffer, on,
+ on & ~VFS_BIO_NEED_BUFSPACE))
+ break;
}
- mtx_unlock(&nblock);
+ if (need_wakeup)
+ wakeup(__DEVOLATILE(void *, &needsbuffer));
+ rw_runlock(&nblock);
}
/*
@@ -497,7 +506,7 @@ runningbufwakeup(struct buf *bp)
static __inline void
bufcountadd(struct buf *bp)
{
- int old;
+ int mask, need_wakeup, old, on;
KASSERT((bp->b_flags & B_INFREECNT) == 0,
("buf %p already counted as free", bp));
@@ -505,14 +514,22 @@ bufcountadd(struct buf *bp)
old = atomic_fetchadd_int(&numfreebuffers, 1);
KASSERT(old >= 0 && old < nbuf,
("numfreebuffers climbed to %d", old + 1));
- mtx_lock(&nblock);
- if (needsbuffer) {
- needsbuffer &= ~VFS_BIO_NEED_ANY;
- if (numfreebuffers >= hifreebuffers)
- needsbuffer &= ~VFS_BIO_NEED_FREE;
- wakeup(&needsbuffer);
+ mask = VFS_BIO_NEED_ANY;
+ if (numfreebuffers >= hifreebuffers)
+ mask |= VFS_BIO_NEED_FREE;
+ rw_rlock(&nblock);
+ for (;;) {
+ need_wakeup = 0;
+ on = needsbuffer;
+ if (on == 0)
+ break;
+ need_wakeup = 1;
+ if (atomic_cmpset_rel_int(&needsbuffer, on, on & ~mask))
+ break;
}
- mtx_unlock(&nblock);
+ if (need_wakeup)
+ wakeup(__DEVOLATILE(void *, &needsbuffer));
+ rw_runlock(&nblock);
}
/*
@@ -756,7 +773,7 @@ bufinit(void)
mtx_init(&bqclean, "bufq clean lock", NULL, MTX_DEF);
mtx_init(&bqdirty, "bufq dirty lock", NULL, MTX_DEF);
mtx_init(&rbreqlock, "runningbufspace lock", NULL, MTX_DEF);
- mtx_init(&nblock, "needsbuffer lock", NULL, MTX_DEF);
+ rw_init(&nblock, "needsbuffer lock");
mtx_init(&bdlock, "buffer daemon lock", NULL, MTX_DEF);
mtx_init(&bdirtylock, "dirty buf lock", NULL, MTX_DEF);
@@ -2054,9 +2071,7 @@ getnewbuf_bufd_help(struct vnode *vp, in
waitmsg = "newbuf";
flags = VFS_BIO_NEED_ANY;
}
- mtx_lock(&nblock);
- needsbuffer |= flags;
- mtx_unlock(&nblock);
+ atomic_set_int(&needsbuffer, flags);
mtx_unlock(&bqclean);
bd_speedup(); /* heeeelp */
@@ -2066,12 +2081,11 @@ getnewbuf_bufd_help(struct vnode *vp, in
td = curthread;
cnt = 0;
wait = MNT_NOWAIT;
- mtx_lock(&nblock);
- while (needsbuffer & flags) {
+ rw_wlock(&nblock);
+ while ((needsbuffer & flags) != 0) {
if (vp != NULL && vp->v_type != VCHR &&
(td->td_pflags & TDP_BUFNEED) == 0) {
- mtx_unlock(&nblock);
-
+ rw_wunlock(&nblock);
/*
* getblk() is called with a vnode locked, and
* some majority of the dirty buffers may as
@@ -2093,15 +2107,16 @@ getnewbuf_bufd_help(struct vnode *vp, in
atomic_add_long(¬bufdflushes, 1);
curthread_pflags_restore(norunbuf);
}
- mtx_lock(&nblock);
+ rw_wlock(&nblock);
if ((needsbuffer & flags) == 0)
break;
}
- if (msleep(&needsbuffer, &nblock, (PRIBIO + 4) | slpflag,
- waitmsg, slptimeo))
+ error = rw_sleep(__DEVOLATILE(void *, &needsbuffer), &nblock,
+ (PRIBIO + 4) | slpflag, waitmsg, slptimeo);
+ if (error != 0)
break;
}
- mtx_unlock(&nblock);
+ rw_wunlock(&nblock);
}
static void
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