| Message ID | 1343187070-27371-2-git-send-email-qemulist@gmail.com |
|---|---|
| State | New |
| Headers | show |
Il 25/07/2012 05:31, Liu Ping Fan ha scritto: > From: Liu Ping Fan <pingfank@linux.vnet.ibm.com> > > rwlock: > qemu_device_tree_mutex > > rd side: > --device_del(destruction of device will be postphoned until unplug > ack from guest), > --pci hot-unplug > --iteration (qdev_reset_all) > > wr side: > --device_add > > Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com> > --- > hw/pci-hotplug.c | 4 ++++ > hw/qdev-monitor.c | 17 ++++++++++++++++- > hw/qdev.c | 2 ++ > 3 files changed, 22 insertions(+), 1 deletions(-) > > diff --git a/hw/pci-hotplug.c b/hw/pci-hotplug.c > index e7fb780..b3b88c1 100644 > --- a/hw/pci-hotplug.c > +++ b/hw/pci-hotplug.c > @@ -265,9 +265,11 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr) > return -1; > } > > + qemu_rwlock_rdlock_devtree(); This is not defined anywhere, is a piece missing in the patch? Paolo
On Wed, Jul 25, 2012 at 5:08 PM, Paolo Bonzini <pbonzini@redhat.com> wrote: > Il 25/07/2012 05:31, Liu Ping Fan ha scritto: >> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com> >> >> rwlock: >> qemu_device_tree_mutex >> >> rd side: >> --device_del(destruction of device will be postphoned until unplug >> ack from guest), >> --pci hot-unplug >> --iteration (qdev_reset_all) >> >> wr side: >> --device_add >> >> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com> >> --- >> hw/pci-hotplug.c | 4 ++++ >> hw/qdev-monitor.c | 17 ++++++++++++++++- >> hw/qdev.c | 2 ++ >> 3 files changed, 22 insertions(+), 1 deletions(-) >> >> diff --git a/hw/pci-hotplug.c b/hw/pci-hotplug.c >> index e7fb780..b3b88c1 100644 >> --- a/hw/pci-hotplug.c >> +++ b/hw/pci-hotplug.c >> @@ -265,9 +265,11 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr) >> return -1; >> } >> >> + qemu_rwlock_rdlock_devtree(); > > This is not defined anywhere, is a piece missing in the patch? > Oh, yes, I miss the patch. In that patch, these rwlock are just place holder. I see there is already try to implement rwlock for qemu. http://lists.gnu.org/archive/html/qemu-devel/2011-10/msg00192.html and is it the time for introduce rwlock for qemu? Thanks, pingfan > Paolo >
On 07/26/2012 03:56 PM, liu ping fan wrote: > On Wed, Jul 25, 2012 at 5:08 PM, Paolo Bonzini <pbonzini@redhat.com> wrote: >> Il 25/07/2012 05:31, Liu Ping Fan ha scritto: >>> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com> >>> >>> rwlock: >>> qemu_device_tree_mutex >>> >>> rd side: >>> --device_del(destruction of device will be postphoned until unplug >>> ack from guest), >>> --pci hot-unplug >>> --iteration (qdev_reset_all) >>> >>> wr side: >>> --device_add >>> >> >> This is not defined anywhere, is a piece missing in the patch? >> > Oh, yes, I miss the patch. In that patch, these rwlock are just place holder. > I see there is already try to implement rwlock for qemu. > http://lists.gnu.org/archive/html/qemu-devel/2011-10/msg00192.html > and is it the time for introduce rwlock for qemu? From the description above, I don't see why it can't be a mutex.
On Thu, Jul 26, 2012 at 9:00 PM, Avi Kivity <avi@redhat.com> wrote: > On 07/26/2012 03:56 PM, liu ping fan wrote: >> On Wed, Jul 25, 2012 at 5:08 PM, Paolo Bonzini <pbonzini@redhat.com> wrote: >>> Il 25/07/2012 05:31, Liu Ping Fan ha scritto: >>>> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com> >>>> >>>> rwlock: >>>> qemu_device_tree_mutex >>>> >>>> rd side: >>>> --device_del(destruction of device will be postphoned until unplug >>>> ack from guest), >>>> --pci hot-unplug >>>> --iteration (qdev_reset_all) >>>> >>>> wr side: >>>> --device_add >>>> >>> >>> This is not defined anywhere, is a piece missing in the patch? >>> >> Oh, yes, I miss the patch. In that patch, these rwlock are just place holder. >> I see there is already try to implement rwlock for qemu. >> http://lists.gnu.org/archive/html/qemu-devel/2011-10/msg00192.html >> and is it the time for introduce rwlock for qemu? > > > From the description above, I don't see why it can't be a mutex. > Searching in the device tree (or MemoryRegion view) can be often in parallel, especially in mmio-dispatch code path Thanx, pingfan > -- > error compiling committee.c: too many arguments to function > >
On 07/26/2012 04:14 PM, liu ping fan wrote: >> >> From the description above, I don't see why it can't be a mutex. >> > Searching in the device tree (or MemoryRegion view) can be often in > parallel, especially in mmio-dispatch code path In mmio dispatch we have a pointer to the object, we don't need to search anything. Is device tree search a hot path?
On Thu, Jul 26, 2012 at 9:15 PM, Avi Kivity <avi@redhat.com> wrote: > On 07/26/2012 04:14 PM, liu ping fan wrote: >>> >>> From the description above, I don't see why it can't be a mutex. >>> >> Searching in the device tree (or MemoryRegion view) can be often in >> parallel, especially in mmio-dispatch code path > > In mmio dispatch we have a pointer to the object, we don't need to > search anything. Is device tree search a hot path? > I think, we need lock to protect searching --phys_page_find() from deleter--DeviceClass:unmap, so rwlock? > > -- > error compiling committee.c: too many arguments to function > >
On 07/26/2012 04:21 PM, liu ping fan wrote: > On Thu, Jul 26, 2012 at 9:15 PM, Avi Kivity <avi@redhat.com> wrote: >> On 07/26/2012 04:14 PM, liu ping fan wrote: >>>> >>>> From the description above, I don't see why it can't be a mutex. >>>> >>> Searching in the device tree (or MemoryRegion view) can be often in >>> parallel, especially in mmio-dispatch code path >> >> In mmio dispatch we have a pointer to the object, we don't need to >> search anything. Is device tree search a hot path? >> > I think, we need lock to protect searching --phys_page_find() from > deleter--DeviceClass:unmap, so rwlock? Better a lock on phys_map (because it is easily replaced by rcu, later). I think phys_map is also better isolated, so it will be easier to find all the placed that need protection and to avoid deadlock.
diff --git a/hw/pci-hotplug.c b/hw/pci-hotplug.c index e7fb780..b3b88c1 100644 --- a/hw/pci-hotplug.c +++ b/hw/pci-hotplug.c @@ -265,9 +265,11 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr) return -1; } + qemu_rwlock_rdlock_devtree(); d = pci_find_device(pci_find_root_bus(dom), bus, PCI_DEVFN(slot, 0)); if (!d) { monitor_printf(mon, "slot %d empty\n", slot); + qemu_rwlock_unlock_devtree(); return -1; } @@ -275,9 +277,11 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr) if (error_is_set(&local_err)) { monitor_printf(mon, "%s\n", error_get_pretty(local_err)); error_free(local_err); + qemu_rwlock_unlock_devtree(); return -1; } + qemu_rwlock_unlock_devtree(); return 0; } diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c index 7915b45..8aec067 100644 --- a/hw/qdev-monitor.c +++ b/hw/qdev-monitor.c @@ -429,14 +429,18 @@ DeviceState *qdev_device_add(QemuOpts *opts) /* find bus */ path = qemu_opt_get(opts, "bus"); + + qemu_rwlock_wrlock_devtree(); if (path != NULL) { bus = qbus_find(path); if (!bus) { + qemu_rwlock_unlock_devtree(); return NULL; } if (strcmp(object_get_typename(OBJECT(bus)), k->bus_type) != 0) { qerror_report(QERR_BAD_BUS_FOR_DEVICE, driver, object_get_typename(OBJECT(bus))); + qemu_rwlock_unlock_devtree(); return NULL; } } else { @@ -444,11 +448,13 @@ DeviceState *qdev_device_add(QemuOpts *opts) if (!bus) { qerror_report(QERR_NO_BUS_FOR_DEVICE, driver, k->bus_type); + qemu_rwlock_unlock_devtree(); return NULL; } } if (qdev_hotplug && !bus->allow_hotplug) { qerror_report(QERR_BUS_NO_HOTPLUG, bus->name); + qemu_rwlock_unlock_devtree(); return NULL; } @@ -466,6 +472,7 @@ DeviceState *qdev_device_add(QemuOpts *opts) } if (qemu_opt_foreach(opts, set_property, qdev, 1) != 0) { qdev_free(qdev); + qemu_rwlock_unlock_devtree(); return NULL; } if (qdev->id) { @@ -478,6 +485,8 @@ DeviceState *qdev_device_add(QemuOpts *opts) OBJECT(qdev), NULL); g_free(name); } + qemu_rwlock_unlock_devtree(); + if (qdev_init(qdev) < 0) { qerror_report(QERR_DEVICE_INIT_FAILED, driver); return NULL; @@ -600,13 +609,19 @@ void qmp_device_del(const char *id, Error **errp) { DeviceState *dev; + /* protect against unplug ack from guest, where we really remove device + * from system + */ + qemu_rwlock_rdlock_devtree(); dev = qdev_find_recursive(sysbus_get_default(), id); if (NULL == dev) { error_set(errp, QERR_DEVICE_NOT_FOUND, id); + qemu_rwlock_unlock_devtree(); return; } - + /* Just remove from system, and drop refcnt there*/ qdev_unplug(dev, errp); + qemu_rwlock_unlock_devtree(); } void qdev_machine_init(void) diff --git a/hw/qdev.c b/hw/qdev.c index af54467..ac55e45 100644 --- a/hw/qdev.c +++ b/hw/qdev.c @@ -230,7 +230,9 @@ static int qbus_reset_one(BusState *bus, void *opaque) void qdev_reset_all(DeviceState *dev) { + qemu_rwlock_rdlock_devtree(); qdev_walk_children(dev, qdev_reset_one, qbus_reset_one, NULL); + qemu_rwlock_unlock_devtree(); } void qbus_reset_all_fn(void *opaque)