Patchwork [PATCHv2,03/12] notifier: event notifier implementation

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Submitter Michael S. Tsirkin
Date Feb. 25, 2010, 6:28 p.m.
Message ID <197f962f6aab3d7fae77ad9f69a3d0dc1ffc07d7.1267122331.git.mst@redhat.com>
Download mbox | patch
Permalink /patch/46270/
State New
Headers show

Comments

Michael S. Tsirkin - Feb. 25, 2010, 6:28 p.m.
event notifiers are slightly generalized eventfd descriptors. Current
implementation depends on eventfd because vhost is the only user, and
vhost depends on eventfd anyway, but a stub is provided for non-eventfd
case.

We'll be able to further generalize this when another user comes along
and we see how to best do this.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 Makefile.target |    1 +
 hw/notifier.c   |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/notifier.h   |   16 ++++++++++++++++
 qemu-common.h   |    1 +
 4 files changed, 68 insertions(+), 0 deletions(-)
 create mode 100644 hw/notifier.c
 create mode 100644 hw/notifier.h
Anthony Liguori - Feb. 25, 2010, 7:22 p.m.
On 02/25/2010 12:28 PM, Michael S. Tsirkin wrote:
> event notifiers are slightly generalized eventfd descriptors. Current
> implementation depends on eventfd because vhost is the only user, and
> vhost depends on eventfd anyway, but a stub is provided for non-eventfd
> case.
>
> We'll be able to further generalize this when another user comes along
> and we see how to best do this.
>
> Signed-off-by: Michael S. Tsirkin<mst@redhat.com>
> ---
>   Makefile.target |    1 +
>   hw/notifier.c   |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>   hw/notifier.h   |   16 ++++++++++++++++
>   qemu-common.h   |    1 +
>   4 files changed, 68 insertions(+), 0 deletions(-)
>   create mode 100644 hw/notifier.c
>   create mode 100644 hw/notifier.h
>
> diff --git a/Makefile.target b/Makefile.target
> index 4c4d397..c1580e9 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -173,6 +173,7 @@ obj-y = vl.o async.o monitor.o pci.o pci_host.o pcie_host.o machine.o gdbstub.o
>   # virtio has to be here due to weird dependency between PCI and virtio-net.
>   # need to fix this properly
>   obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-pci.o virtio-serial-bus.o
> +obj-y += notifier.o
>   obj-y += rwhandler.o
>   obj-$(CONFIG_KVM) += kvm.o kvm-all.o
>   obj-$(CONFIG_ISA_MMIO) += isa_mmio.o
> diff --git a/hw/notifier.c b/hw/notifier.c
> new file mode 100644
> index 0000000..dff38de
> --- /dev/null
> +++ b/hw/notifier.c
> @@ -0,0 +1,50 @@
> +#include "hw.h"
> +#include "notifier.h"
> +#ifdef CONFIG_EVENTFD
> +#include<sys/eventfd.h>
> +#endif
> +
> +int event_notifier_init(EventNotifier *e, int active)
> +{
> +#ifdef CONFIG_EVENTFD
> +	int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
> +	if (fd<  0)
> +		return -errno;
> +	e->fd = fd;
> +	return 0;
> +#else
> +	return -ENOSYS;
> +#endif
> +}
> +
> +void event_notifier_cleanup(EventNotifier *e)
> +{
> +	close(e->fd);
> +}
> +
> +int event_notifier_get_fd(EventNotifier *e)
> +{
> +	return e->fd;
> +}
> +
> +int event_notifier_test_and_clear(EventNotifier *e)
> +{
> +	uint64_t value;
> +	int r = read(e->fd,&value, sizeof value);
> +	return r == sizeof value;
>    

Probably should handle EINTR, no?

> +}
> +
> +int event_notifier_test(EventNotifier *e)
> +{
> +	uint64_t value;
> +	int r = read(e->fd,&value, sizeof value);
>    

Coding Style is not quite explicit here but we always use sizeof(value).

> +	if (r == sizeof value) {
> +		/* restore previous value. */
> +		int s = write(e->fd,&value, sizeof value);
> +		/* never blocks because we use EFD_SEMAPHORE.
> +		 * If we didn't we'd get EAGAIN on overflow
> +		 * and we'd have to write code to ignore it. */
> +		assert(s == sizeof value);
> +	}
> +	return r == sizeof value;
> +}
> diff --git a/hw/notifier.h b/hw/notifier.h
> new file mode 100644
> index 0000000..24117ea
> --- /dev/null
> +++ b/hw/notifier.h
> @@ -0,0 +1,16 @@
>    

Needs copyright/license.

Thanks for doing this abstraction, I'm really happy with it over direct 
eventfd usage.

Regards,

Anthony Liguori

> +#ifndef QEMU_EVENT_NOTIFIER_H
> +#define QEMU_EVENT_NOTIFIER_H
> +
> +#include "qemu-common.h"
> +
> +struct EventNotifier {
> +	int fd;
> +};
> +
> +int event_notifier_init(EventNotifier *, int active);
> +void event_notifier_cleanup(EventNotifier *);
> +int event_notifier_get_fd(EventNotifier *);
> +int event_notifier_test_and_clear(EventNotifier *);
> +int event_notifier_test(EventNotifier *);
> +
> +#endif
> diff --git a/qemu-common.h b/qemu-common.h
> index 805be1a..f12a8f5 100644
> --- a/qemu-common.h
> +++ b/qemu-common.h
> @@ -227,6 +227,7 @@ typedef struct uWireSlave uWireSlave;
>   typedef struct I2SCodec I2SCodec;
>   typedef struct DeviceState DeviceState;
>   typedef struct SSIBus SSIBus;
> +typedef struct EventNotifier EventNotifier;
>
>   typedef uint64_t pcibus_t;
>
>
Michael S. Tsirkin - Feb. 28, 2010, 7:59 p.m.
On Thu, Feb 25, 2010 at 01:22:04PM -0600, Anthony Liguori wrote:
> On 02/25/2010 12:28 PM, Michael S. Tsirkin wrote:
>> event notifiers are slightly generalized eventfd descriptors. Current
>> implementation depends on eventfd because vhost is the only user, and
>> vhost depends on eventfd anyway, but a stub is provided for non-eventfd
>> case.
>>
>> We'll be able to further generalize this when another user comes along
>> and we see how to best do this.
>>
>> Signed-off-by: Michael S. Tsirkin<mst@redhat.com>
>> ---
>>   Makefile.target |    1 +
>>   hw/notifier.c   |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>   hw/notifier.h   |   16 ++++++++++++++++
>>   qemu-common.h   |    1 +
>>   4 files changed, 68 insertions(+), 0 deletions(-)
>>   create mode 100644 hw/notifier.c
>>   create mode 100644 hw/notifier.h
>>
>> diff --git a/Makefile.target b/Makefile.target
>> index 4c4d397..c1580e9 100644
>> --- a/Makefile.target
>> +++ b/Makefile.target
>> @@ -173,6 +173,7 @@ obj-y = vl.o async.o monitor.o pci.o pci_host.o pcie_host.o machine.o gdbstub.o
>>   # virtio has to be here due to weird dependency between PCI and virtio-net.
>>   # need to fix this properly
>>   obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-pci.o virtio-serial-bus.o
>> +obj-y += notifier.o
>>   obj-y += rwhandler.o
>>   obj-$(CONFIG_KVM) += kvm.o kvm-all.o
>>   obj-$(CONFIG_ISA_MMIO) += isa_mmio.o
>> diff --git a/hw/notifier.c b/hw/notifier.c
>> new file mode 100644
>> index 0000000..dff38de
>> --- /dev/null
>> +++ b/hw/notifier.c
>> @@ -0,0 +1,50 @@
>> +#include "hw.h"
>> +#include "notifier.h"
>> +#ifdef CONFIG_EVENTFD
>> +#include<sys/eventfd.h>
>> +#endif
>> +
>> +int event_notifier_init(EventNotifier *e, int active)
>> +{
>> +#ifdef CONFIG_EVENTFD
>> +	int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
>> +	if (fd<  0)
>> +		return -errno;
>> +	e->fd = fd;
>> +	return 0;
>> +#else
>> +	return -ENOSYS;
>> +#endif
>> +}
>> +
>> +void event_notifier_cleanup(EventNotifier *e)
>> +{
>> +	close(e->fd);
>> +}
>> +
>> +int event_notifier_get_fd(EventNotifier *e)
>> +{
>> +	return e->fd;
>> +}
>> +
>> +int event_notifier_test_and_clear(EventNotifier *e)
>> +{
>> +	uint64_t value;
>> +	int r = read(e->fd,&value, sizeof value);
>> +	return r == sizeof value;
>>    
>
> Probably should handle EINTR, no?

No, nonblocking eventfd read never returns EINTR.


>> +}
>> +
>> +int event_notifier_test(EventNotifier *e)
>> +{
>> +	uint64_t value;
>> +	int r = read(e->fd,&value, sizeof value);
>>    
>
> Coding Style is not quite explicit here but we always use sizeof(value).
>
>> +	if (r == sizeof value) {
>> +		/* restore previous value. */
>> +		int s = write(e->fd,&value, sizeof value);
>> +		/* never blocks because we use EFD_SEMAPHORE.
>> +		 * If we didn't we'd get EAGAIN on overflow
>> +		 * and we'd have to write code to ignore it. */
>> +		assert(s == sizeof value);
>> +	}
>> +	return r == sizeof value;
>> +}
>> diff --git a/hw/notifier.h b/hw/notifier.h
>> new file mode 100644
>> index 0000000..24117ea
>> --- /dev/null
>> +++ b/hw/notifier.h
>> @@ -0,0 +1,16 @@
>>    
>
> Needs copyright/license.
>
> Thanks for doing this abstraction, I'm really happy with it over direct  
> eventfd usage.
>
> Regards,
>
> Anthony Liguori
>
>> +#ifndef QEMU_EVENT_NOTIFIER_H
>> +#define QEMU_EVENT_NOTIFIER_H
>> +
>> +#include "qemu-common.h"
>> +
>> +struct EventNotifier {
>> +	int fd;
>> +};
>> +
>> +int event_notifier_init(EventNotifier *, int active);
>> +void event_notifier_cleanup(EventNotifier *);
>> +int event_notifier_get_fd(EventNotifier *);
>> +int event_notifier_test_and_clear(EventNotifier *);
>> +int event_notifier_test(EventNotifier *);
>> +
>> +#endif
>> diff --git a/qemu-common.h b/qemu-common.h
>> index 805be1a..f12a8f5 100644
>> --- a/qemu-common.h
>> +++ b/qemu-common.h
>> @@ -227,6 +227,7 @@ typedef struct uWireSlave uWireSlave;
>>   typedef struct I2SCodec I2SCodec;
>>   typedef struct DeviceState DeviceState;
>>   typedef struct SSIBus SSIBus;
>> +typedef struct EventNotifier EventNotifier;
>>
>>   typedef uint64_t pcibus_t;
>>
>>    
>
>

Patch

diff --git a/Makefile.target b/Makefile.target
index 4c4d397..c1580e9 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -173,6 +173,7 @@  obj-y = vl.o async.o monitor.o pci.o pci_host.o pcie_host.o machine.o gdbstub.o
 # virtio has to be here due to weird dependency between PCI and virtio-net.
 # need to fix this properly
 obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-pci.o virtio-serial-bus.o
+obj-y += notifier.o
 obj-y += rwhandler.o
 obj-$(CONFIG_KVM) += kvm.o kvm-all.o
 obj-$(CONFIG_ISA_MMIO) += isa_mmio.o
diff --git a/hw/notifier.c b/hw/notifier.c
new file mode 100644
index 0000000..dff38de
--- /dev/null
+++ b/hw/notifier.c
@@ -0,0 +1,50 @@ 
+#include "hw.h"
+#include "notifier.h"
+#ifdef CONFIG_EVENTFD
+#include <sys/eventfd.h>
+#endif
+
+int event_notifier_init(EventNotifier *e, int active)
+{
+#ifdef CONFIG_EVENTFD
+	int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
+	if (fd < 0)
+		return -errno;
+	e->fd = fd;
+	return 0;
+#else
+	return -ENOSYS;
+#endif
+}
+
+void event_notifier_cleanup(EventNotifier *e)
+{
+	close(e->fd);
+}
+
+int event_notifier_get_fd(EventNotifier *e)
+{
+	return e->fd;
+}
+
+int event_notifier_test_and_clear(EventNotifier *e)
+{
+	uint64_t value;
+	int r = read(e->fd, &value, sizeof value);
+	return r == sizeof value;
+}
+
+int event_notifier_test(EventNotifier *e)
+{
+	uint64_t value;
+	int r = read(e->fd, &value, sizeof value);
+	if (r == sizeof value) {
+		/* restore previous value. */
+		int s = write(e->fd, &value, sizeof value);
+		/* never blocks because we use EFD_SEMAPHORE.
+		 * If we didn't we'd get EAGAIN on overflow
+		 * and we'd have to write code to ignore it. */
+		assert(s == sizeof value);
+	}
+	return r == sizeof value;
+}
diff --git a/hw/notifier.h b/hw/notifier.h
new file mode 100644
index 0000000..24117ea
--- /dev/null
+++ b/hw/notifier.h
@@ -0,0 +1,16 @@ 
+#ifndef QEMU_EVENT_NOTIFIER_H
+#define QEMU_EVENT_NOTIFIER_H
+
+#include "qemu-common.h"
+
+struct EventNotifier {
+	int fd;
+};
+
+int event_notifier_init(EventNotifier *, int active);
+void event_notifier_cleanup(EventNotifier *);
+int event_notifier_get_fd(EventNotifier *);
+int event_notifier_test_and_clear(EventNotifier *);
+int event_notifier_test(EventNotifier *);
+
+#endif
diff --git a/qemu-common.h b/qemu-common.h
index 805be1a..f12a8f5 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -227,6 +227,7 @@  typedef struct uWireSlave uWireSlave;
 typedef struct I2SCodec I2SCodec;
 typedef struct DeviceState DeviceState;
 typedef struct SSIBus SSIBus;
+typedef struct EventNotifier EventNotifier;
 
 typedef uint64_t pcibus_t;