From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:54758) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TG23O-0004dE-JO for qemu-devel@nongnu.org; Mon, 24 Sep 2012 02:22:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TG23N-00033e-NC for qemu-devel@nongnu.org; Mon, 24 Sep 2012 02:22:02 -0400 Received: from [222.73.24.84] (port=29506 helo=song.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TG23N-00033X-Dm for qemu-devel@nongnu.org; Mon, 24 Sep 2012 02:22:01 -0400 Message-ID: <505FFD45.2050804@cn.fujitsu.com> Date: Mon, 24 Sep 2012 14:27:17 +0800 From: Wen Congyang MIME-Version: 1.0 References: <1348247243-12446-1-git-send-email-lcapitulino@redhat.com> <1348247243-12446-3-git-send-email-lcapitulino@redhat.com> In-Reply-To: <1348247243-12446-3-git-send-email-lcapitulino@redhat.com> Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] [PATCH 2/3] qmp: dump-guest-memory: don't spin if non-blocking fd would block List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: jan.kiszka@siemens.com, aliguori@us.ibm.com, qemu-devel@nongnu.org, d.hatayama@jp.fujitsu.com, armbru@redhat.com At 09/22/2012 01:07 AM, Luiz Capitulino Wrote: > fd_write_vmcore() will indefinitely spin for a non-blocking > file-descriptor that would block. However, if the fd is non-blocking, > how does it make sense to spin? > > Change this behavior to return an error instead. > > Note that this can only happen with an fd provided by a management > application. The fd opened internally by dump-guest-memory is blocking. > > Signed-off-by: Luiz Capitulino > --- > dump.c | 13 +++---------- > 1 file changed, 3 insertions(+), 10 deletions(-) > > diff --git a/dump.c b/dump.c > index 2bf8d8d..5eea015 100644 > --- a/dump.c > +++ b/dump.c > @@ -100,18 +100,11 @@ static void dump_error(DumpState *s, const char *reason) > static int fd_write_vmcore(void *buf, size_t size, void *opaque) > { > DumpState *s = opaque; > - int fd = s->fd; > size_t writen_size; > > - /* The fd may be passed from user, and it can be non-blocked */ > - while (size) { > - writen_size = qemu_write_full(fd, buf, size); > - if (writen_size != size && errno != EAGAIN) { Hmm, if the fd is a blocking fd, errno can't be EAGAIN. So the function doesn't spin. What problems do you meet? Thanks Wen Congyang > - return -1; > - } > - > - buf += writen_size; > - size -= writen_size; > + writen_size = qemu_write_full(s->fd, buf, size); > + if (writen_size != size) { > + return -1; > } > > return 0;