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From 46979f6e61d0afc31be31dab797f60c4f41c3de5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Fri, 20 Jul 2018 12:18:00 +0200
Subject: [PATCH 255/268] hw/char/serial: retry write if EAGAIN
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RH-Author: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: <20180720121800.18952-3-marcandre.lureau@redhat.com>
Patchwork-id: 81455
O-Subject: [RHEL-7.6 qemu-kvm-rhev PATCH v2 2/2] hw/char/serial: retry write if EAGAIN
Bugzilla: 1592817
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Markus Armbruster <armbru@redhat.com>
RH-Acked-by: John Snow <jsnow@redhat.com>

If the chardev returns -1 with EAGAIN errno on write(), it should try
to send it again (EINTR is handled by the chardev itself).

This fixes commit 019288bf137183bf3407c9824655b753bfafc99f
"hw/char/serial: Only retry if qemu_chr_fe_write returns 0"

Tested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180716110755.12499-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit f3575af130c700cea060b51a89008a76dae22259)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/char/serial.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/hw/char/serial.c b/hw/char/serial.c
index d4057bf..478f9a8 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -262,15 +262,20 @@ static void serial_xmit(SerialState *s)
         if (s->mcr & UART_MCR_LOOP) {
             /* in loopback mode, say that we just received a char */
             serial_receive1(s, &s->tsr, 1);
-        } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) == 0 &&
-                   s->tsr_retry < MAX_XMIT_RETRY) {
-            assert(s->watch_tag == 0);
-            s->watch_tag =
-                qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
-                                      serial_watch_cb, s);
-            if (s->watch_tag > 0) {
-                s->tsr_retry++;
-                return;
+        } else {
+            int rc = qemu_chr_fe_write(&s->chr, &s->tsr, 1);
+
+            if ((rc == 0 ||
+                 (rc == -1 && errno == EAGAIN)) &&
+                s->tsr_retry < MAX_XMIT_RETRY) {
+                assert(s->watch_tag == 0);
+                s->watch_tag =
+                    qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
+                                          serial_watch_cb, s);
+                if (s->watch_tag > 0) {
+                    s->tsr_retry++;
+                    return;
+                }
             }
         }
         s->tsr_retry = 0;
-- 
1.8.3.1