exec-migration: handle EINTR in popen_get_buffer()

Sometimes, upon interrupt, fread returns with no data, and
the (incoming exec) migration fails.

Fix by retrying on such a case.

(cherry picked from commit 8a67ec4d84f7db9add9a0b017a968d340fbfb807)

Signed-off-by: Uri Lublin <uril@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/savevm.c b/savevm.c
index 54137f87f4..c7bc398d97 100644
--- a/savevm.c
+++ b/savevm.c
@@ -210,7 +210,14 @@ static int popen_put_buffer(void *opaque, const uint8_t *buf, int64_t pos, int s
 static int popen_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size)
 {
     QEMUFilePopen *s = opaque;
-    return fread(buf, 1, size, s->popen_file);
+    FILE *fp = s->popen_file;
+    int bytes;
+
+    do {
+        clearerr(fp);
+        bytes = fread(buf, 1, size, fp);
+    } while ((bytes == 0) && ferror(fp) && (errno == EINTR));
+    return bytes;
 }
 
 static int popen_close(void *opaque)