On Fri, Jan 29, 2021 at 04:53:12PM +0100, Greg Kurz wrote: > 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. > > Signed-off-by: Greg Kurz <[email protected]> > --- > tools/virtiofsd/fuse_virtio.c | 42 +++++++++++++++++++++++------------ > 1 file changed, 28 insertions(+), 14 deletions(-) > > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c > index ddcefee4272f..7ea269c4b65d 100644 > --- a/tools/virtiofsd/fuse_virtio.c > +++ b/tools/virtiofsd/fuse_virtio.c > @@ -187,6 +187,24 @@ 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. > + */ > +#define VU_DISPATCH_LOCK_OP(op) \ > +static inline void vu_dispatch_##op(struct fv_VuDev *vud) \ > +{ \ > + int ret = pthread_rwlock_##op(&vud->vu_dispatch_rwlock); \ > + assert(ret == 0); \ > +} > + > +VU_DISPATCH_LOCK_OP(rdlock); > +VU_DISPATCH_LOCK_OP(wrlock); > +VU_DISPATCH_LOCK_OP(unlock); > +
I generally do not prefer using macros to define functions as searching to functions declarations/definitions becomes harder. But I see lot of people prefer that because they can reduce number of lines of code. Apart from that one issue of using rdlock in fv_queue_thread(), stefan pointed, it looks good to me. Reviewed-by: Vivek Goyal <[email protected]> Vivek > /* > * 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 +258,12 @@ 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 +421,12 @@ 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 +576,12 @@ 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 +614,6 @@ 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 +662,7 @@ 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_wrlock(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 +688,7 @@ 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 +815,6 @@ 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 +840,11 @@ 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__); > -- > 2.26.2 >
