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Fix the spechash lock order reversal by keeping an updated sum

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of v_usecount in the dev_t which vcount() can return without
locking any vnodes.

Seen by:	jhb
This commit is contained in:
Poul-Henning Kamp 2002-10-24 19:38:56 +00:00
parent 7c0c26b4c4
commit a2fb4feded
3 changed files with 30 additions and 19 deletions
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47
sys/kern/vfs_subr.c
View File

@ -1954,6 +1954,17 @@ bdevvp(dev, vpp)
return (0);
}
static void
v_incr_usecount(struct vnode *vp, int delta)
{
vp->v_usecount += delta;
if (vp->v_type == VCHR) {
mtx_lock(&spechash_mtx);
vp->v_rdev->si_usecount += delta;
mtx_unlock(&spechash_mtx);
}
}
/*
* Add vnode to the alias list hung off the dev_t.
*
@ -2022,9 +2033,12 @@ addalias(nvp, dev)
KASSERT(nvp->v_type == VCHR, ("addalias on non-special vnode"));
nvp->v_rdev = dev;
VI_LOCK(nvp);
mtx_lock(&spechash_mtx);
SLIST_INSERT_HEAD(&dev->si_hlist, nvp, v_specnext);
dev->si_usecount += nvp->v_usecount;
mtx_unlock(&spechash_mtx);
VI_UNLOCK(nvp);
}
/*
@ -2057,7 +2071,7 @@ vget(vp, flags, td)
return (ENOENT);
}
vp->v_usecount++;
v_incr_usecount(vp, 1);
if (VSHOULDBUSY(vp))
vbusy(vp);
@ -2072,7 +2086,7 @@ vget(vp, flags, td)
* not try to recycle it.
*/
VI_LOCK(vp);
vp->v_usecount--;
v_incr_usecount(vp, -1);
if (VSHOULDFREE(vp))
vfree(vp);
else
@ -2092,7 +2106,7 @@ void
vref(struct vnode *vp)
{
VI_LOCK(vp);
vp->v_usecount++;
v_incr_usecount(vp, 1);
VI_UNLOCK(vp);
}
@ -2138,14 +2152,14 @@ vrele(vp)
if (vp->v_usecount > 1) {
vp->v_usecount--;
v_incr_usecount(vp, -1);
VI_UNLOCK(vp);
return;
}
if (vp->v_usecount == 1) {
vp->v_usecount--;
v_incr_usecount(vp, -1);
/*
* We must call VOP_INACTIVE with the node locked.
* If we are doing a vput, the node is already locked,
@ -2190,13 +2204,13 @@ vput(vp)
("vput: missed vn_close"));
if (vp->v_usecount > 1) {
vp->v_usecount--;
v_incr_usecount(vp, -1);
VOP_UNLOCK(vp, LK_INTERLOCK, td);
return;
}
if (vp->v_usecount == 1) {
vp->v_usecount--;
v_incr_usecount(vp, -1);
/*
* We must call VOP_INACTIVE with the node locked.
* If we are doing a vput, the node is already locked,
@ -2459,7 +2473,7 @@ vclean(vp, flags, td)
* generate a race against ourselves to recycle it.
*/
if ((active = vp->v_usecount))
vp->v_usecount++;
v_incr_usecount(vp, 1);
/*
* Prevent the vnode from being recycled or brought into use while we
@ -2526,7 +2540,8 @@ vclean(vp, flags, td)
* has already been called.
*/
VI_LOCK(vp);
if (--vp->v_usecount <= 0) {
v_incr_usecount(vp, -1);
if (vp->v_usecount <= 0) {
#ifdef DIAGNOSTIC
if (vp->v_usecount < 0 || vp->v_writecount != 0) {
vprint("vclean: bad ref count", vp);
@ -2675,10 +2690,12 @@ vgonel(vp, td)
* if it is on one.
*/
if (vp->v_type == VCHR && vp->v_rdev != NULL && vp->v_rdev != NODEV) {
VI_LOCK(vp);
mtx_lock(&spechash_mtx);
SLIST_REMOVE(&vp->v_rdev->si_hlist, vp, vnode, v_specnext);
freedev(vp->v_rdev);
vp->v_rdev->si_usecount -= vp->v_usecount;
mtx_unlock(&spechash_mtx);
VI_UNLOCK(vp);
vp->v_rdev = NULL;
}
@ -2741,18 +2758,10 @@ int
vcount(vp)
struct vnode *vp;
{
struct vnode *vq;
int count;
count = 0;
mtx_lock(&spechash_mtx);
SLIST_FOREACH(vq, &vp->v_rdev->si_hlist, v_specnext) {
if (vq != vp)
VI_LOCK(vq);
count += vq->v_usecount;
if (vq != vp)
VI_UNLOCK(vq);
}
count = vp->v_rdev->si_usecount;
mtx_unlock(&spechash_mtx);
return (count);
}

1
sys/sys/conf.h
View File

@ -82,6 +82,7 @@ struct cdev {
uid_t si_uid;
gid_t si_gid;
mode_t si_mode;
u_long si_usecount;
union {
struct {
struct tty *__sit_tty;

1
sys/sys/linedisc.h
View File

@ -82,6 +82,7 @@ struct cdev {
uid_t si_uid;
gid_t si_gid;
mode_t si_mode;
u_long si_usecount;
union {
struct {
struct tty *__sit_tty;