search for: mutex

Hello, CVS 07/31/03. Test with 130+ PSTN-to-SIP calls. Asterisk gets locked ... grep -e "Error" -e "eventually" p-console chan_sip.c line 1453 (sip_alloc): Error obtaining mutex: Device or resource busy chan_sip.c line 1453 (sip_alloc): Got it eventually... chan_sip.c line 1453 (sip_alloc): Error obtaining mutex: Device or resource busy chan_sip.c line 1453 (sip_alloc): Got it eventually... chan_sip.c line 1453 (sip_alloc): Error obtaining mutex: Device or resource busy ch...

...r is sometimes held for a long time (for example, when devices handle requests). This also prevents us from calling functions that might sleep (such as kthread_flush_work() in the next patch), and thus having to release and retake the lock. For these reasons, let's replace the spinlock with a mutex that gives us more flexibility. Suggested-by: Jason Wang <jasowang at redhat.com> Signed-off-by: Stefano Garzarella <sgarzare at redhat.com> --- drivers/vdpa/vdpa_sim/vdpa_sim.h | 4 ++-- drivers/vdpa/vdpa_sim/vdpa_sim.c | 34 ++++++++++++++-------------- drivers/vdpa/vdpa_si...

...t: %> mkdir llvm-svn-build %> cd llvm-svn-build/ %> ccmake ../llvm-svn # Basically only tweak the install prefix in ccmake, configure, generate %> make ... [ 2%] Built target LLVMSupport [ 3%] Built target LLVMSystem Linking CXX executable ../../bin/tblgen ../../lib/libLLVMSystem.a(Mutex.cpp.o): In function `llvm::sys::Mutex::tryacquire()': Mutex.cpp:(.text+0x3f): undefined reference to `pthread_mutex_trylock' ../../lib/libLLVMSystem.a(Mutex.cpp.o): In function `llvm::sys::Mutex::Mutex(bool)': Mutex.cpp:(.text+0x1bb): undefined reference to `pthread_mutexattr_init'...

Commit 78139c94dc8c ("net: vhost: lock the vqs one by one") moved the vq lock to improve scalability, but introduced a possible deadlock in vhost-iotlb. vhost_iotlb_notify_vq() now takes vq->mutex while holding the device's IOTLB spinlock. And on the vhost_iotlb_miss() path, the spinlock is taken while holding vq->mutex. As long as we hold dev->mutex to prevent an ioctl from modifying vq->poll concurrently, we can safely call vhost_poll_queue() without holding vq->mutex. Sin...

Commit 78139c94dc8c ("net: vhost: lock the vqs one by one") moved the vq lock to improve scalability, but introduced a possible deadlock in vhost-iotlb. vhost_iotlb_notify_vq() now takes vq->mutex while holding the device's IOTLB spinlock. And on the vhost_iotlb_miss() path, the spinlock is taken while holding vq->mutex. As long as we hold dev->mutex to prevent an ioctl from modifying vq->poll concurrently, we can safely call vhost_poll_queue() without holding vq->mutex. Sin...

Refactor code to make sure features are only accessed under VQ mutex. This makes everything simpler, no need for RCU here anymore. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- This is on top of the recent pull request that I sent. drivers/vhost/vhost.h | 11 +++-------- drivers/vhost/net.c | 8 +++----- drivers/vhost/scsi.c | 22 ++++++++++...

Refactor code to make sure features are only accessed under VQ mutex. This makes everything simpler, no need for RCU here anymore. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- This is on top of the recent pull request that I sent. drivers/vhost/vhost.h | 11 +++-------- drivers/vhost/net.c | 8 +++----- drivers/vhost/scsi.c | 22 ++++++++++...

These three patches (for discussion only, NOT to be applied) implement a mutex system that lets the user limit the number of libguestfs instances that can be launched per host. There are two uses that I have identified for this: firstly so we can enable parallel-tests (the default in automake >= 1.13) without blowing up the host. Secondly oVirt has raised concerns about...

...index b13c6b4..f52008b 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -294,8 +294,11 @@ static void vhost_vq_meta_reset(struct vhost_dev *d) > { > int i; > > - for (i = 0; i < d->nvqs; ++i) > + for (i = 0; i < d->nvqs; ++i) { > + mutex_lock(&d->vqs[i]->mutex); > __vhost_vq_meta_reset(d->vqs[i]); > + mutex_unlock(&d->vqs[i]->mutex); > + } > } > > static void vhost_vq_reset(struct vhost_dev *dev, > @@ -891,20 +894,6 @@ static inline void __user *__vhost_get_user(struct vhost_virtq...

...index b13c6b4..f52008b 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -294,8 +294,11 @@ static void vhost_vq_meta_reset(struct vhost_dev *d) > { > int i; > > - for (i = 0; i < d->nvqs; ++i) > + for (i = 0; i < d->nvqs; ++i) { > + mutex_lock(&d->vqs[i]->mutex); > __vhost_vq_meta_reset(d->vqs[i]); > + mutex_unlock(&d->vqs[i]->mutex); > + } > } > > static void vhost_vq_reset(struct vhost_dev *dev, > @@ -891,20 +894,6 @@ static inline void __user *__vhost_get_user(struct vhost_virtq...

Asias He (4): vhost-net: Always access vq->private_data under vq mutex vhost-test: Always access vq->private_data under vq mutex vhost-scsi: Always access vq->private_data under vq mutex vhost: Remove custom vhost rcu usage drivers/vhost/net.c | 37 ++++++++++++++++--------------------- drivers/vhost/scsi.c | 17 ++++++----------- drivers/vhost/test.c...

Asias He (4): vhost-net: Always access vq->private_data under vq mutex vhost-test: Always access vq->private_data under vq mutex vhost-scsi: Always access vq->private_data under vq mutex vhost: Remove custom vhost rcu usage drivers/vhost/net.c | 37 ++++++++++++++++--------------------- drivers/vhost/scsi.c | 17 ++++++----------- drivers/vhost/test.c...

On Mon, Dec 10, 2018 at 05:44:52PM +0800, Jason Wang wrote: > When we try to do rx busy polling in tx path in commit 441abde4cd84 > ("net: vhost: add rx busy polling in tx path"), we lock rx vq mutex > after tx vq mutex is held. This may lead deadlock so we try to lock vq > one by one in commit 78139c94dc8c ("net: vhost: lock the vqs one by > one"). With this commit, we avoid the deadlock with the assumption > that handle_rx() and handle_tx() run in a same process. But thi...

On Mon, Dec 10, 2018 at 05:44:52PM +0800, Jason Wang wrote: > When we try to do rx busy polling in tx path in commit 441abde4cd84 > ("net: vhost: add rx busy polling in tx path"), we lock rx vq mutex > after tx vq mutex is held. This may lead deadlock so we try to lock vq > one by one in commit 78139c94dc8c ("net: vhost: lock the vqs one by > one"). With this commit, we avoid the deadlock with the assumption > that handle_rx() and handle_tx() run in a same process. But thi...

As I''ve mentioned before, Sync and Mutex are very similar, and Mutex is very simple. Their locking algorithm (for exclusive locking) is essentially identical. And in some detailed examinations of Mutex''s behavior, there''s nothing superficially wrong with it. It''s pure ruby, so there are no funny memory alloca...

On Tue, 2014-06-03 at 00:30 +0300, Michael S. Tsirkin wrote: > All memory accesses are done under some VQ mutex. > So lock/unlock all VQs is a faster equivalent of synchronize_rcu() > for memory access changes. > Some guests cause a lot of these changes, so it's helpful > to make them faster. > > Reported-by: "Gonglei (Arei)" <arei.gonglei at huawei.com> > Signed-off...

On Tue, 2014-06-03 at 00:30 +0300, Michael S. Tsirkin wrote: > All memory accesses are done under some VQ mutex. > So lock/unlock all VQs is a faster equivalent of synchronize_rcu() > for memory access changes. > Some guests cause a lot of these changes, so it's helpful > to make them faster. > > Reported-by: "Gonglei (Arei)" <arei.gonglei at huawei.com> > Signed-off...

On Fri, Jun 6, 2014 at 10:57 PM, Kostya Serebryany <kcc at google.com> wrote: > As for the deadlocks, indeed it is possible to add deadlock detection > directly to std::mutex and std::spinlock code. > It may even end up being more efficient than a standalone deadlock > detector -- > but only if we can add an extra word to the mutex/spinlock object. > The deadlock detector's overhead comes primarily from two tasks: > 1. get the metadata for the lock...

Refactor code to make sure features are only accessed under VQ mutex. This makes everything simpler, no need for RCU here anymore. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Note: this is on top of my last pull request drivers/vhost/vhost.h | 11 +++-------- drivers/vhost/net.c | 8 +++----- drivers/vhost/scsi.c | 22 +++++++++++++-------...

Refactor code to make sure features are only accessed under VQ mutex. This makes everything simpler, no need for RCU here anymore. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> --- Note: this is on top of my last pull request drivers/vhost/vhost.h | 11 +++-------- drivers/vhost/net.c | 8 +++----- drivers/vhost/scsi.c | 22 +++++++++++++-------...