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[Xen-devel] [PATCH linux-2.6.18-xen] fix xenbus_transaction_start() hang

To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] [PATCH linux-2.6.18-xen] fix xenbus_transaction_start() hang caused by double xenbus_transaction_end()
From: Laszlo Ersek <lersek@xxxxxxxxxx>
Date: Thu, 12 May 2011 12:24:17 +0200
Cc: Ky Srinivasan <ksrinivasan@xxxxxxxxxx>
Delivery-date: Thu, 12 May 2011 03:24:24 -0700
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fix xenbus_transaction_start() hang caused by double xenbus_transaction_end()

vbd_resize() up_read()'s xs_state.suspend_mutex twice in a row via double
xenbus_transaction_end() calls. The next down_read() in
xenbus_transaction_start() (at eg. the next resize attempt) hangs.

See RHBZ#618317.

Thanks for considering.

Signed-off-by: Laszlo Ersek <lersek@xxxxxxxxxx>
---
 drivers/xen/blkback/vbd.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/xen/blkback/vbd.c b/drivers/xen/blkback/vbd.c
--- a/drivers/xen/blkback/vbd.c
+++ b/drivers/xen/blkback/vbd.c
@@ -156,6 +156,7 @@
                goto again;
        if (err)
                printk(KERN_WARNING "Error ending transaction");
+       return;
 abort:
        xenbus_transaction_end(xbt, 1);
 }


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