commit 595ab64169be9063d64c3b1aa1c249fbe2662221
author Paolo Bonzini <pbonzini@redhat.com> Tue Aug 07 11:07:59 2012 +0200
committer Paolo Bonzini <pbonzini@redhat.com> Fri Nov 02 18:35:07 2012 +0100
tree 7b0188e657d3ca6471eb87d3d49d799a81397745
parent 1c12e1f5b2ce215ee25b4a4e365e76269edf911c

migration: handle EAGAIN while reading QEMUFile

This will never happen right now (the assertion would fail).  The
next patch will set the socket or pipe in non-blocking mode, thus
enabling this part of the code.

Coroutines can just stop whenever they want with qemu_coroutine_yield.
As soon as select tells the main loop that the migration stream is
readable, the coroutine is re-entered directly in qemu_get_buffer,
where it will read more data and pass it to the loading routines.

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

savevm.c

diff --git a/savevm.c b/savevm.c
index cdad3ad..5d04d59 100644
--- a/savevm.c
+++ b/savevm.c
@@ -200,13 +200,22 @@
     QEMUFileSocket *s = opaque;
     ssize_t len;
 
-    do {
+    for (;;) {
         len = qemu_recv(s->fd, buf, size, 0);
-    } while (len == -1 && socket_error() == EINTR);
+        if (len != -1) {
+            break;
+        }
+        if (socket_error() == EAGAIN) {
+            assert(qemu_in_coroutine());
+            qemu_coroutine_yield();
+        } else if (socket_error() != EINTR) {
+            break;
+        }
+    }
 
-    if (len == -1)
+    if (len == -1) {
         len = -socket_error();
-
+    }
     return len;
 }
 
@@ -237,10 +246,19 @@
     FILE *fp = s->stdio_file;
     int bytes;
 
-    do {
+    for (;;) {
         clearerr(fp);
         bytes = fread(buf, 1, size, fp);
-    } while ((bytes == 0) && ferror(fp) && (errno == EINTR));
+        if (bytes != 0 || !ferror(fp)) {
+            break;
+        }
+        if (errno == EAGAIN) {
+            assert(qemu_in_coroutine());
+            qemu_coroutine_yield();
+        } else if (errno != EINTR) {
+            break;
+        }
+    }
     return bytes;
 }