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Commit 76ce7618 authored by Daniel De Graaf's avatar Daniel De Graaf Committed by Jeremy Fitzhardinge
Browse files

xenbus: add missing wakeup in concurrent read/write 



If an application has a dedicated read thread watching xenbus and
another thread writes an XS_WATCH message that generates a synthetic
"OK" reply, this reply will be enqueued in the buffer without waking up
the reader. This can cause a deadlock in the application if it then
waits for the read thread to receive the queued message.

Signed-off-by: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>

commit e752969f502a511e83f841aa01d6cd332e6d85a0
Author: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Date:   Tue Sep 7 11:21:52 2010 -0400

    xenbus: fix deadlock in concurrent read/write

    If an application has a dedicated read thread watching xenbus and another
    thread writes an XS_WATCH message that generates a synthetic "OK" reply,
    this reply will be enqueued in the buffer without waking up the reader.
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 6d6df2e4

drivers/xen/xenfs/xenbus.c

+1 −0
Original line number Diff line number Diff line
@@ -405,6 +405,7 @@ static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u) 


		mutex_lock(&u->reply_mutex);

		rc = queue_reply(&u->read_buffers, &reply, sizeof(reply));

		wake_up(&u->read_waitq);

		mutex_unlock(&u->reply_mutex);

	}