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virtiofsd: vu_dispatch locking should never fail 

pthread_rwlock_rdlock() and pthread_rwlock_wrlock() can fail if a
deadlock condition is detected or the current thread already owns
the lock. They can also fail, like pthread_rwlock_unlock(), if the
mutex wasn't properly initialized. None of these are ever expected
to happen with fv_VuDev::vu_dispatch_rwlock.

Some users already check the return value and assert, some others
don't. Introduce rdlock/wrlock/unlock wrappers that just do the
former and use them everywhere for improved consistency and
robustness.

This is just cleanup. It doesn't fix any actual issue.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <20210203182434.93870-1-groug@kaod.org>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
master
Greg Kurz 2021-02-03 19:24:34 +01:00 committed by Dr. David Alan Gilbert
parent 0958ee89b6
commit 525a3030a8
1 changed files with 35 additions and 14 deletions
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49
tools/virtiofsd/fuse_virtio.c
View File

@ -187,6 +187,31 @@ static void copy_iov(struct iovec *src_iov, int src_count,
}
}
/*
* pthread_rwlock_rdlock() and pthread_rwlock_wrlock can fail if
* a deadlock condition is detected or the current thread already
* owns the lock. They can also fail, like pthread_rwlock_unlock(),
* if the mutex wasn't properly initialized. None of these are ever
* expected to happen.
*/
static void vu_dispatch_rdlock(struct fv_VuDev *vud)
{
int ret = pthread_rwlock_rdlock(&vud->vu_dispatch_rwlock);
assert(ret == 0);
}
static void vu_dispatch_wrlock(struct fv_VuDev *vud)
{
int ret = pthread_rwlock_wrlock(&vud->vu_dispatch_rwlock);
assert(ret == 0);
}
static void vu_dispatch_unlock(struct fv_VuDev *vud)
{
int ret = pthread_rwlock_unlock(&vud->vu_dispatch_rwlock);
assert(ret == 0);
}
/*
* Called back by ll whenever it wants to send a reply/message back
* The 1st element of the iov starts with the fuse_out_header
@ -240,12 +265,12 @@ int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch,
copy_iov(iov, count, in_sg, in_num, tosend_len);
pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_rdlock(qi->virtio_dev);
pthread_mutex_lock(&qi->vq_lock);
vu_queue_push(dev, q, elem, tosend_len);
vu_queue_notify(dev, q);
pthread_mutex_unlock(&qi->vq_lock);
pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_unlock(qi->virtio_dev);
req->reply_sent = true;
@ -403,12 +428,12 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch,
ret = 0;
pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_rdlock(qi->virtio_dev);
pthread_mutex_lock(&qi->vq_lock);
vu_queue_push(dev, q, elem, tosend_len);
vu_queue_notify(dev, q);
pthread_mutex_unlock(&qi->vq_lock);
pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_unlock(qi->virtio_dev);
err:
if (ret == 0) {
@ -558,12 +583,12 @@ out:
fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n", __func__,
elem->index);
pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_rdlock(qi->virtio_dev);
pthread_mutex_lock(&qi->vq_lock);
vu_queue_push(dev, q, elem, 0);
vu_queue_notify(dev, q);
pthread_mutex_unlock(&qi->vq_lock);
pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_unlock(qi->virtio_dev);
}
pthread_mutex_destroy(&req->ch.lock);
@ -596,7 +621,6 @@ static void *fv_queue_thread(void *opaque)
qi->qidx, qi->kick_fd);
while (1) {
struct pollfd pf[2];
int ret;
pf[0].fd = qi->kick_fd;
pf[0].events = POLLIN;
@ -645,8 +669,7 @@ static void *fv_queue_thread(void *opaque)
break;
}
/* Mutual exclusion with virtio_loop() */
ret = pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock);
assert(ret == 0); /* there is no possible error case */
vu_dispatch_rdlock(qi->virtio_dev);
pthread_mutex_lock(&qi->vq_lock);
/* out is from guest, in is too guest */
unsigned int in_bytes, out_bytes;
@ -672,7 +695,7 @@ static void *fv_queue_thread(void *opaque)
}
pthread_mutex_unlock(&qi->vq_lock);
pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_unlock(qi->virtio_dev);
/* Process all the requests. */
if (!se->thread_pool_size && req_list != NULL) {
@ -799,7 +822,6 @@ int virtio_loop(struct fuse_session *se)
while (!fuse_session_exited(se)) {
struct pollfd pf[1];
bool ok;
int ret;
pf[0].fd = se->vu_socketfd;
pf[0].events = POLLIN;
pf[0].revents = 0;
@ -825,12 +847,11 @@ int virtio_loop(struct fuse_session *se)
assert(pf[0].revents & POLLIN);
fuse_log(FUSE_LOG_DEBUG, "%s: Got VU event\n", __func__);
/* Mutual exclusion with fv_queue_thread() */
ret = pthread_rwlock_wrlock(&se->virtio_dev->vu_dispatch_rwlock);
assert(ret == 0); /* there is no possible error case */
vu_dispatch_wrlock(se->virtio_dev);
ok = vu_dispatch(&se->virtio_dev->dev);
pthread_rwlock_unlock(&se->virtio_dev->vu_dispatch_rwlock);
vu_dispatch_unlock(se->virtio_dev);
if (!ok) {
fuse_log(FUSE_LOG_ERR, "%s: vu_dispatch failed\n", __func__);