From 53628efbc8aa7a7ab5354d24b971f4d69452151d Mon Sep 17 00:00:00 2001
From: "Daniel P. Berrange" <berrange@redhat.com>
Date: Thu, 31 Mar 2016 16:29:27 +0100
Subject: char: fix broken EAGAIN retry on OS-X due to errno clobbering

Some of the chardev I/O paths really want to write the
complete data buffer even though the channel is in
non-blocking mode. To achieve this they look for EAGAIN
and g_usleep() for 100ms. Unfortunately the code is set
to check errno == EAGAIN a second time, after the g_usleep()
call has completed. On OS-X at least, g_usleep clobbers
errno to ETIMEDOUT, causing the retry to be skipped.

This failure to retry means the full data isn't written
to the chardev backend, which causes various failures
including making the tests/ahci-test qtest hang.

Rather than playing games trying to reset errno just
simplify the code to use a goto to retry instead of a
a loop.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1459438168-8146-2-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-char.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

(limited to 'qemu-char.c')

diff --git a/qemu-char.c b/qemu-char.c
index 270819aec3..93fd7333f3 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -225,12 +225,12 @@ static void qemu_chr_fe_write_log(CharDriverState *s,
     }
 
     while (done < len) {
-        do {
-            ret = write(s->logfd, buf + done, len - done);
-            if (ret == -1 && errno == EAGAIN) {
-                g_usleep(100);
-            }
-        } while (ret == -1 && errno == EAGAIN);
+    retry:
+        ret = write(s->logfd, buf + done, len - done);
+        if (ret == -1 && errno == EAGAIN) {
+            g_usleep(100);
+            goto retry;
+        }
 
         if (ret <= 0) {
             return;
@@ -246,12 +246,12 @@ static int qemu_chr_fe_write_buffer(CharDriverState *s, const uint8_t *buf, int
 
     qemu_mutex_lock(&s->chr_write_lock);
     while (*offset < len) {
-        do {
-            res = s->chr_write(s, buf + *offset, len - *offset);
-            if (res == -1 && errno == EAGAIN) {
-                g_usleep(100);
-            }
-        } while (res == -1 && errno == EAGAIN);
+    retry:
+        res = s->chr_write(s, buf + *offset, len - *offset);
+        if (res < 0 && errno == EAGAIN) {
+            g_usleep(100);
+            goto retry;
+        }
 
         if (res <= 0) {
             break;
@@ -333,12 +333,12 @@ int qemu_chr_fe_read_all(CharDriverState *s, uint8_t *buf, int len)
     }
 
     while (offset < len) {
-        do {
-            res = s->chr_sync_read(s, buf + offset, len - offset);
-            if (res == -1 && errno == EAGAIN) {
-                g_usleep(100);
-            }
-        } while (res == -1 && errno == EAGAIN);
+    retry:
+        res = s->chr_sync_read(s, buf + offset, len - offset);
+        if (res == -1 && errno == EAGAIN) {
+            g_usleep(100);
+            goto retry;
+        }
 
         if (res == 0) {
             break;
-- 
cgit v1.2.3


From 64c800f808748522727847b9cdc73412f22dffb9 Mon Sep 17 00:00:00 2001
From: "Daniel P. Berrange" <berrange@redhat.com>
Date: Fri, 18 Mar 2016 18:00:41 +0000
Subject: char: ensure all clients are in non-blocking mode

Only some callers of tcp_chr_new_client are putting the
socket client into non-blocking mode. Move the call to
qio_channel_set_blocking() into the tcp_chr_new_client
method to guarantee that all code paths set non-blocking
mode

Reported-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Reported-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1458324041-22709-1-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 qemu-char.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'qemu-char.c')

diff --git a/qemu-char.c b/qemu-char.c
index 93fd7333f3..b597ee19ca 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3081,6 +3081,8 @@ static int tcp_chr_new_client(CharDriverState *chr, QIOChannelSocket *sioc)
     s->sioc = sioc;
     object_ref(OBJECT(sioc));
 
+    qio_channel_set_blocking(s->ioc, false, NULL);
+
     if (s->do_nodelay) {
         qio_channel_set_delay(s->ioc, false);
     }
@@ -3112,7 +3114,6 @@ static int tcp_chr_add_client(CharDriverState *chr, int fd)
     if (!sioc) {
         return -1;
     }
-    qio_channel_set_blocking(QIO_CHANNEL(sioc), false, NULL);
     ret = tcp_chr_new_client(chr, sioc);
     object_unref(OBJECT(sioc));
     return ret;
-- 
cgit v1.2.3