From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37598) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhGrI-0004F9-Et for qemu-devel@nongnu.org; Tue, 06 Sep 2016 09:56:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bhGrH-0006BH-Hz for qemu-devel@nongnu.org; Tue, 06 Sep 2016 09:56:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49406) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bhGrH-0006B7-Bt for qemu-devel@nongnu.org; Tue, 06 Sep 2016 09:56:15 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E21B3C0567A3 for ; Tue, 6 Sep 2016 13:56:14 +0000 (UTC) From: "Daniel P. Berrange" Date: Tue, 6 Sep 2016 14:56:03 +0100 Message-Id: <1473170165-540-3-git-send-email-berrange@redhat.com> In-Reply-To: <1473170165-540-1-git-send-email-berrange@redhat.com> References: <1473170165-540-1-git-send-email-berrange@redhat.com> Subject: [Qemu-devel] [PATCH v2 2/4] sclpconsolelm: remove bogus check for -EAGAIN List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Paolo Bonzini , "Daniel P. Berrange" The write_console_data() method in sclpconsole-lm.c checks whether the return value of qemu_chr_fe_write() has the value of -EAGAIN and if so then increments the buffer offset by the value of EAGAIN. Fortunately qemu_chr_fe_write() will never return EAGAIN directly, rather it returns -1 with errno set to EAGAIN, so this broken code path was not reachable. The behaviour on EAGAIN was stil bad though, causing the write_console_data() to busy_wait repeatedly calling qemu_chr_fe_write() with no sleep between iters. Just remove all this loop logic and replace with a call to qemu_chr_fe_write_all(). Acked-by: Cornelia Huck Signed-off-by: Daniel P. Berrange --- hw/char/sclpconsole-lm.c | 18 +++--------------- 1 file changed, 3 insertions(+), 15 deletions(-) diff --git a/hw/char/sclpconsole-lm.c b/hw/char/sclpconsole-lm.c index a22ad8d..8cb0026 100644 --- a/hw/char/sclpconsole-lm.c +++ b/hw/char/sclpconsole-lm.c @@ -201,21 +201,9 @@ static int write_console_data(SCLPEvent *event, const uint8_t *buf, int len) return len; } - buf_offset = buf; - while (len > 0) { - ret = qemu_chr_fe_write(scon->chr, buf, len); - if (ret == 0) { - /* a pty doesn't seem to be connected - no error */ - len = 0; - } else if (ret == -EAGAIN || (ret > 0 && ret < len)) { - len -= ret; - buf_offset += ret; - } else { - len = 0; - } - } - - return ret; + /* XXX this blocks entire thread. Rewrite to use + * qemu_chr_fe_write and background I/O callbacks */ + return qemu_chr_fe_write_all(scon->chr, buf, len); } static int process_mdb(SCLPEvent *event, MDBO *mdbo) -- 2.7.4