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[Qemu-devel] [RESEND] [PATCH 1/2] migrate.c: migrate_fd_put_buffer(): Do


From: Uri Lublin
Subject: [Qemu-devel] [RESEND] [PATCH 1/2] migrate.c: migrate_fd_put_buffer(): Do not busyloop: stop writing if EWOULDBLOCK
Date: Tue, 10 Feb 2009 05:04:25 +0200
User-agent: Thunderbird 2.0.0.19 (X11/20090105)

Theoretically the migration code is non-blocking, designed for live migration.

Practically migrate_fd_put_buffer busy-loops trying to write. That's since
on many machines EWOULDBLOCK==EAGAIN (e.g. look in
<linux>/include/asm-generic/errno.h).
Busy looping is much worse then blocking (in case a write actually blocks).

Fixed by removing "(s->get_error(s)) == EWOULDBLOCK)" from the while condition.

Signed-off-by: Uri Lublin <address@hidden>
---
 migration.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/migration.c b/migration.c
index 0ef777a..e8bafa6 100644
--- a/migration.c
+++ b/migration.c
@@ -168,7 +168,7 @@ ssize_t migrate_fd_put_buffer(void *opaque, const void *data, size_t size)

     do {
         ret = s->write(s, data, size);
- } while (ret == -1 && ((s->get_error(s)) == EINTR || (s->get_error(s)) == EWOULDBLOCK));
+    } while (ret == -1 && s->get_error(s) == EINTR);

     if (ret == -1)
         ret = -(s->get_error(s));
--
1.6.0.6







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