[Qemu-devel] [PATCH 0/3] Event signaling tweaks

[Qemu-devel] [PATCH 0/3] Event signaling tweaks

[Paolo Bonzini]

This series of three patches makes two small changes to qemu_event_read
and qemu_event_increment.  These are preparatory to merging eventfd
usage in the iothread from qemu-kvm (which would have conflicts, so it
has to be done with some care).

Paolo Bonzini (3):
  do not loop on an incomplete io_thread_fd read
  loop qemu_event_increment if we have an EINTR
  fix placement of config-host.h inclusion

 osdep.c |    7 ++++---
 vl.c    |   12 ++++++++----
 2 files changed, 12 insertions(+), 7 deletions(-)

[Qemu-devel] [PATCH 1/3] do not loop on an incomplete io_thread_fd read

[Paolo Bonzini]

No need to loop if less than a full buffer is read, the next
read would return EAGAIN.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 vl.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/vl.c b/vl.c
index 6f1e1ab..46c1118 100644
--- a/vl.c
+++ b/vl.c
@@ -3210,12 +3210,12 @@ static void qemu_event_read(void *opaque)
 {
     int fd = (unsigned long)opaque;
     ssize_t len;
+    char buffer[512];
 
     /* Drain the notify pipe */
     do {
-        char buffer[512];
         len = read(fd, buffer, sizeof(buffer));
-    } while ((len == -1 && errno == EINTR) || len > 0);
+    } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
 }
 
 static int qemu_event_init(void)
-- 
1.6.6

[Qemu-devel] [PATCH 2/3] loop write in qemu_event_increment upon EINTR

[Paolo Bonzini]

Same as what qemu-kvm does.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 vl.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/vl.c b/vl.c
index 46c1118..f150eca 100644
--- a/vl.c
+++ b/vl.c
@@ -3198,8 +3198,12 @@ static void qemu_event_increment(void)
     if (io_thread_fd == -1)
         return;
 
-    ret = write(io_thread_fd, &byte, sizeof(byte));
-    if (ret < 0 && (errno != EINTR && errno != EAGAIN)) {
+    do {
+        ret = write(io_thread_fd, &byte, sizeof(byte));
+    } while (ret < 0 && errno == EINTR);
+
+    /* EAGAIN is fine, a read must be pending.  */
+    if (ret < 0 && errno != EAGAIN) {
         fprintf(stderr, "qemu_event_increment: write() filed: %s\n",
                 strerror(errno));
         exit (1);
-- 
1.6.6

[Qemu-devel] [PATCH 3/3] fix placement of config-host.h inclusion

[Paolo Bonzini]

The #ifdef CONFIG_SOLARIS below was useless without this patch.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 osdep.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/osdep.c b/osdep.c
index cf3a2c6..9059f01 100644
--- a/osdep.c
+++ b/osdep.c
@@ -28,14 +28,15 @@
 #include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>
+
+/* Needed early for CONFIG_BSD etc. */
+#include "config-host.h"
+
 #ifdef CONFIG_SOLARIS
 #include <sys/types.h>
 #include <sys/statvfs.h>
 #endif
 
-/* Needed early for CONFIG_BSD etc. */
-#include "config-host.h"
-
 #ifdef _WIN32
 #include <windows.h>
 #elif defined(CONFIG_BSD)
-- 
1.6.6

Re: [Qemu-devel] [PATCH 1/3] do not loop on an incomplete io_thread_fd read

[Anthony Liguori]

On 02/02/2010 01:33 PM, Paolo Bonzini wrote:
> No need to loop if less than a full buffer is read, the next
> read would return EAGAIN.
>
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
>    

Applied all.  Thanks.

Regards,

Anthony Liguori
> ---
>   vl.c |    4 ++--
>   1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 6f1e1ab..46c1118 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -3210,12 +3210,12 @@ static void qemu_event_read(void *opaque)
>   {
>       int fd = (unsigned long)opaque;
>       ssize_t len;
> +    char buffer[512];
>
>       /* Drain the notify pipe */
>       do {
> -        char buffer[512];
>           len = read(fd, buffer, sizeof(buffer));
> -    } while ((len == -1&&  errno == EINTR) || len>  0);
> +    } while ((len == -1&&  errno == EINTR) || len == sizeof(buffer));
>   }
>
>   static int qemu_event_init(void)
>