[PATCH 04/10] chardev/char-fe: don't allow EAGAIN from blocking read

[Roman Kagan]

As its name suggests, ChardevClass.chr_sync_read is supposed to do a
blocking read.  The only implementation of it, tcp_chr_sync_read, does
set the underlying io channel to the blocking mode indeed.

Therefore a failure return with EAGAIN is not expected from this call.

So do not retry it in qemu_chr_fe_read_all; instead place an assertion
that it doesn't fail with EAGAIN.

Signed-off-by: Roman Kagan <rvka...@yandex-team.ru>
---
 chardev/char-fe.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index 7789f7be9c..f94efe928e 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -68,13 +68,10 @@ int qemu_chr_fe_read_all(CharBackend *be, uint8_t *buf, int 
len)
     }
 
     while (offset < len) {
-    retry:
         res = CHARDEV_GET_CLASS(s)->chr_sync_read(s, buf + offset,
                                                   len - offset);
-        if (res == -1 && errno == EAGAIN) {
-            g_usleep(100);
-            goto retry;
-        }
+        /* ->chr_sync_read should block */
+        assert(!(res < 0 && errno == EAGAIN));
 
         if (res == 0) {
             break;
-- 
2.33.1