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Switch from using the vnode interlock to a private mutex in fifo_open()

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to avoid lock order problems when manipulating the sockets associated
with the fifo.

Minor optimization of a couple of calls to fifo_cleanup() from
fifo_open().
This commit is contained in:
Don Lewis 2004-05-17 20:16:40 +00:00
parent af03fdc4cc
commit 2526dc2b61
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=129355
1 changed files with 23 additions and 24 deletions
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47
sys/fs/fifofs/fifo_vnops.c
View File

@ -122,6 +122,9 @@ static struct vnodeopv_desc fifo_vnodeop_opv_desc =
VNODEOP_SET(fifo_vnodeop_opv_desc);
struct mtx fifo_mtx;
MTX_SYSINIT(fifo, &fifo_mtx, "fifo mutex", MTX_DEF);
int
fifo_vnoperate(ap)
struct vop_generic_args /* {
@ -217,28 +220,25 @@ fifo_open(ap)
* the vnode lock.
*
* Protect the increment of fi_readers and fi_writers and the
* associated calls to wakeup() with the vnode interlock in
* addition to the vnode lock. This allows the vnode lock to
* be dropped for the msleep() calls below, and using the vnode
* interlock as the msleep() mutex prevents the wakeup from
* being missed.
* associated calls to wakeup() with the fifo mutex in addition
* to the vnode lock. This allows the vnode lock to be dropped
* for the msleep() calls below, and using the fifo mutex with
* msleep() prevents the wakeup from being missed.
*/
VI_LOCK(vp);
mtx_lock(&fifo_mtx);
if (ap->a_mode & FREAD) {
fip->fi_readers++;
if (fip->fi_readers == 1) {
fip->fi_writesock->so_state &= ~SS_CANTSENDMORE;
if (fip->fi_writers > 0) {
wakeup(&fip->fi_writers);
VI_UNLOCK(vp);
sowwakeup(fip->fi_writesock);
VI_LOCK(vp);
}
}
}
if (ap->a_mode & FWRITE) {
if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
VI_UNLOCK(vp);
mtx_unlock(&fifo_mtx);
return (ENXIO);
}
fip->fi_writers++;
@ -246,26 +246,25 @@ fifo_open(ap)
fip->fi_readsock->so_state &= ~SS_CANTRCVMORE;
if (fip->fi_readers > 0) {
wakeup(&fip->fi_readers);
VI_UNLOCK(vp);
sorwakeup(fip->fi_writesock);
VI_LOCK(vp);
}
}
}
if ((ap->a_mode & O_NONBLOCK) == 0) {
if ((ap->a_mode & FREAD) && fip->fi_writers == 0) {
VOP_UNLOCK(vp, 0, td);
error = msleep(&fip->fi_readers, VI_MTX(vp),
PCATCH | PSOCK, "fifoor", 0);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY | LK_INTERLOCK, td);
error = msleep(&fip->fi_readers, &fifo_mtx,
PDROP | PCATCH | PSOCK, "fifoor", 0);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
if (error) {
fip->fi_readers--;
if (fip->fi_readers == 0)
if (fip->fi_readers == 0) {
socantsendmore(fip->fi_writesock);
fifo_cleanup(vp);
fifo_cleanup(vp);
}
return (error);
}
VI_LOCK(vp);
mtx_lock(&fifo_mtx);
/*
* We must have got woken up because we had a writer.
* That (and not still having one) is the condition
@ -274,15 +273,15 @@ fifo_open(ap)
}
if ((ap->a_mode & FWRITE) && fip->fi_readers == 0) {
VOP_UNLOCK(vp, 0, td);
error = msleep(&fip->fi_writers, VI_MTX(vp),
PCATCH | PSOCK, "fifoow", 0);
vn_lock(vp,
LK_EXCLUSIVE | LK_RETRY | LK_INTERLOCK, td);
error = msleep(&fip->fi_writers, &fifo_mtx,
PDROP | PCATCH | PSOCK, "fifoow", 0);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
if (error) {
fip->fi_writers--;
if (fip->fi_writers == 0)
if (fip->fi_writers == 0) {
socantrcvmore(fip->fi_readsock);
fifo_cleanup(vp);
fifo_cleanup(vp);
}
return (error);
}
/*
@ -293,7 +292,7 @@ fifo_open(ap)
return (0);
}
}
VI_UNLOCK(vp);
mtx_unlock(&fifo_mtx);
return (0);
}