[Qemu-devel] [PATCH] migration: Clean up use of g_poll() in socket_writev_buffer()

[Qemu-devel] [PATCH] migration: Clean up use of g_poll() in socket_writev_buffer()

[Markus Armbruster]

socket_writev_buffer() writes in a loop, using g_poll() to block.  If
g_poll() fails, it tries to write more before the file descriptor is
ready.  In theory, this could go into a tight loop.  In practice,
errors other than EINTR are really unlikely, and when they happen,
we're probably screwed anyway, so we can just as well loop.

Clean it up a bit: retry poll on EINTR, keep ignoring other errors.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
Let me stress once again: this is *not* a bug fix, it's cleanup!  If
you don't like it, you can safely ignore it.  We'll then mark the spot
as intentional in the Coverity dashboard.

 migration/qemu-file-unix.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/qemu-file-unix.c b/migration/qemu-file-unix.c
index c503b02..6ca53e7 100644
--- a/migration/qemu-file-unix.c
+++ b/migration/qemu-file-unix.c
@@ -72,7 +72,8 @@ static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
             pfd.fd = s->fd;
             pfd.events = G_IO_OUT | G_IO_ERR;
             pfd.revents = 0;
-            g_poll(&pfd, 1 /* 1 fd */, -1 /* no timeout */);
+            TFR(err = g_poll(&pfd, 1, -1 /* no timeout */));
+            /* Errors other than EINTR intentionally ignored */
         }
      }
 
-- 
2.4.3

Re: [Qemu-devel] [PATCH] migration: Clean up use of g_poll() in socket_writev_buffer()

[Paolo Bonzini]

On 01/12/2015 14:34, Markus Armbruster wrote:
> socket_writev_buffer() writes in a loop, using g_poll() to block.  If
> g_poll() fails, it tries to write more before the file descriptor is
> ready.  In theory, this could go into a tight loop.  In practice,
> errors other than EINTR are really unlikely, and when they happen,
> we're probably screwed anyway, so we can just as well loop.
> 
> Clean it up a bit: retry poll on EINTR, keep ignoring other errors.
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
> Let me stress once again: this is *not* a bug fix, it's cleanup!  If
> you don't like it, you can safely ignore it.  We'll then mark the spot
> as intentional in the Coverity dashboard.
> 
>  migration/qemu-file-unix.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/qemu-file-unix.c b/migration/qemu-file-unix.c
> index c503b02..6ca53e7 100644
> --- a/migration/qemu-file-unix.c
> +++ b/migration/qemu-file-unix.c
> @@ -72,7 +72,8 @@ static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
>              pfd.fd = s->fd;
>              pfd.events = G_IO_OUT | G_IO_ERR;
>              pfd.revents = 0;
> -            g_poll(&pfd, 1 /* 1 fd */, -1 /* no timeout */);
> +            TFR(err = g_poll(&pfd, 1, -1 /* no timeout */));
> +            /* Errors other than EINTR intentionally ignored */
>          }
>       }
>  
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Re: [Qemu-devel] [PATCH] migration: Clean up use of g_poll() in socket_writev_buffer()

[Juan Quintela]

Markus Armbruster <armbru@redhat.com> wrote:
> socket_writev_buffer() writes in a loop, using g_poll() to block.  If
> g_poll() fails, it tries to write more before the file descriptor is
> ready.  In theory, this could go into a tight loop.  In practice,
> errors other than EINTR are really unlikely, and when they happen,
> we're probably screwed anyway, so we can just as well loop.
>
> Clean it up a bit: retry poll on EINTR, keep ignoring other errors.
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Included in next migration pull request.

Thanks.


> ---
> Let me stress once again: this is *not* a bug fix, it's cleanup!  If
> you don't like it, you can safely ignore it.  We'll then mark the spot
> as intentional in the Coverity dashboard.
>
>  migration/qemu-file-unix.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/migration/qemu-file-unix.c b/migration/qemu-file-unix.c
> index c503b02..6ca53e7 100644
> --- a/migration/qemu-file-unix.c
> +++ b/migration/qemu-file-unix.c
> @@ -72,7 +72,8 @@ static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
>              pfd.fd = s->fd;
>              pfd.events = G_IO_OUT | G_IO_ERR;
>              pfd.revents = 0;
> -            g_poll(&pfd, 1 /* 1 fd */, -1 /* no timeout */);
> +            TFR(err = g_poll(&pfd, 1, -1 /* no timeout */));
> +            /* Errors other than EINTR intentionally ignored */
>          }
>       }