linux/drivers/xen/xenbus
Juergen Gross a8fabb3852 xen/xenbus: fix self-deadlock after killing user process
In case a user process using xenbus has open transactions and is killed
e.g. via ctrl-C the following cleanup of the allocated resources might
result in a deadlock due to trying to end a transaction in the xenbus
worker thread:

[ 2551.474706] INFO: task xenbus:37 blocked for more than 120 seconds.
[ 2551.492215]       Tainted: P           OE     5.0.0-29-generic #5
[ 2551.510263] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 2551.528585] xenbus          D    0    37      2 0x80000080
[ 2551.528590] Call Trace:
[ 2551.528603]  __schedule+0x2c0/0x870
[ 2551.528606]  ? _cond_resched+0x19/0x40
[ 2551.528632]  schedule+0x2c/0x70
[ 2551.528637]  xs_talkv+0x1ec/0x2b0
[ 2551.528642]  ? wait_woken+0x80/0x80
[ 2551.528645]  xs_single+0x53/0x80
[ 2551.528648]  xenbus_transaction_end+0x3b/0x70
[ 2551.528651]  xenbus_file_free+0x5a/0x160
[ 2551.528654]  xenbus_dev_queue_reply+0xc4/0x220
[ 2551.528657]  xenbus_thread+0x7de/0x880
[ 2551.528660]  ? wait_woken+0x80/0x80
[ 2551.528665]  kthread+0x121/0x140
[ 2551.528667]  ? xb_read+0x1d0/0x1d0
[ 2551.528670]  ? kthread_park+0x90/0x90
[ 2551.528673]  ret_from_fork+0x35/0x40

Fix this by doing the cleanup via a workqueue instead.

Reported-by: James Dingwall <james@dingwall.me.uk>
Fixes: fd8aa9095a ("xen: optimize xenbus driver for multiple concurrent xenstore accesses")
Cc: <stable@vger.kernel.org> # 4.11
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2019-10-02 16:40:11 -04:00
..
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xenbus.h xenbus: Avoid deadlock during suspend due to open transactions 2019-05-28 17:32:15 -04:00
xenbus_client.c xen: drop writing error messages to xenstore 2018-10-26 09:17:16 +02:00
xenbus_comms.c xenbus: track caller request id 2018-02-17 09:40:33 +01:00
xenbus_dev_backend.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xenbus_dev_frontend.c xen/xenbus: fix self-deadlock after killing user process 2019-10-02 16:40:11 -04:00
xenbus_probe.c xen: export device state to sysfs 2018-08-28 17:37:40 -04:00
xenbus_probe_backend.c xen: modify xenstore watch event interface 2017-02-09 11:26:49 -05:00
xenbus_probe_frontend.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
xenbus_xs.c xenbus: Avoid deadlock during suspend due to open transactions 2019-05-28 17:32:15 -04:00