On Wed, Feb 03, 2021 at 05:08:57PM +0100, Greg Kurz wrote: > On Wed, 3 Feb 2021 10:59:34 -0500 > Vivek Goyal <[email protected]> wrote: > > > 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. > > > > Well, I must admit I hesitated since this doesn't gain much in > terms of LoC compared to the expanded version. I'm perfectly > fine with dropping the macro in my v2 if this looks better > to you.
If you are posting V2 anyway, so lets do it. Agreed, we are not saving many lines where so why to use macros to define functions. Vivek > > > 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 > > > > > >
