Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Mon, 04 Aug 2014 17:48:31 +0100 | Subject | [PATCH 3.2 21/94] xen/manage: fix potential deadlock when resuming the console |
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3.2.62-rc1 review patch. If anyone has any objections, please let me know.
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From: David Vrabel <david.vrabel@citrix.com>
commit 1b6478231c6f5f844185acb32045cf195028cfce upstream.
Calling xen_console_resume() in xen_suspend() causes a warning because it locks irq_mapping_update_lock (a mutex) and this may sleep. If a userspace process is using the evtchn device then this mutex may be locked at the point of the stop_machine() call and xen_console_resume() would then deadlock.
Resuming the console after stop_machine() returns avoids this deadlock.
Signed-off-by: David Vrabel <david.vrabel@citrix.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/xen/manage.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/xen/manage.c +++ b/drivers/xen/manage.c @@ -93,7 +93,6 @@ static int xen_suspend(void *data) if (!si->cancelled) { xen_irq_resume(); - xen_console_resume(); xen_timer_resume(); } @@ -149,6 +148,10 @@ static void do_suspend(void) err = stop_machine(xen_suspend, &si, cpumask_of(0)); + /* Resume console as early as possible. */ + if (!si.cancelled) + xen_console_resume(); + dpm_resume_noirq(si.cancelled ? PMSG_THAW : PMSG_RESTORE); if (err) {
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