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authorDaniel De Graaf <dgdegra@tycho.nsa.gov>2010-09-08 18:10:42 -0400
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2010-09-09 10:48:22 +1000
commit7808121b9a1e44ef12fecd49fa6c268f27a150fc (patch)
tree5536cceff908e630d1a15c4f63abd7210ed4973b /drivers/xen/xenfs
parent76ce7618f9a24f7b13958c67f7d5ccfcdab71475 (diff)
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xenbus: avoid zero returns from read()
It is possible to get a zero return from read() in instances where the queue is not empty but has no elements with data to deliver to the user. Since a zero return from read is an error indicator, resume waiting or return -EAGAIN (for a nonblocking fd) in this case. Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Diffstat (limited to 'drivers/xen/xenfs')
-rw-r--r--drivers/xen/xenfs/xenbus.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/xen/xenfs/xenbus.c b/drivers/xen/xenfs/xenbus.c
index c4c7db8363e7..55791dd1105f 100644
--- a/drivers/xen/xenfs/xenbus.c
+++ b/drivers/xen/xenfs/xenbus.c
@@ -120,6 +120,7 @@ static ssize_t xenbus_file_read(struct file *filp,
int ret;
mutex_lock(&u->reply_mutex);
+again:
while (list_empty(&u->read_buffers)) {
mutex_unlock(&u->reply_mutex);
if (filp->f_flags & O_NONBLOCK)
@@ -158,6 +159,8 @@ static ssize_t xenbus_file_read(struct file *filp,
struct read_buffer, list);
}
}
+ if (i == 0)
+ goto again;
out:
mutex_unlock(&u->reply_mutex);