This is a note to let you know that I've just added the patch titled
xen/manage: Always freeze/thaw processes when suspend/resuming
to the 3.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-manage-always-freeze-thaw-processes-when-suspend-resuming.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 61a734d305e16944b42730ef582a7171dc733321 Mon Sep 17 00:00:00 2001
From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Date: Mon, 18 Aug 2014 10:41:36 +0100
Subject: xen/manage: Always freeze/thaw processes when suspend/resuming
From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
commit 61a734d305e16944b42730ef582a7171dc733321 upstream.
Always freeze processes when suspending and thaw processes when resuming
to prevent a race noticeable with HVM guests.
This prevents a deadlock where the khubd kthread (which is designed to
be freezable) acquires a usb device lock and then tries to allocate
memory which requires the disk which hasn't been resumed yet.
Meanwhile, the xenwatch thread deadlocks waiting for the usb device
lock.
Freezing processes fixes this because the khubd thread is only thawed
after the xenwatch thread finishes resuming all the devices.
Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/xen/manage.c | 7 -------
1 file changed, 7 deletions(-)
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -103,16 +103,11 @@ static void do_suspend(void)
shutting_down = SHUTDOWN_SUSPEND;
-#ifdef CONFIG_PREEMPT
- /* If the kernel is preemptible, we need to freeze all the processes
- to prevent them from being in the middle of a pagetable update
- during suspend. */
err = freeze_processes();
if (err) {
pr_err("%s: freeze failed %d\n", __func__, err);
goto out;
}
-#endif
err = dpm_suspend_start(PMSG_FREEZE);
if (err) {
@@ -157,10 +152,8 @@ out_resume:
dpm_resume_end(si.cancelled ? PMSG_THAW : PMSG_RESTORE);
out_thaw:
-#ifdef CONFIG_PREEMPT
thaw_processes();
out:
-#endif
shutting_down = SHUTDOWN_INVALID;
}
#endif /* CONFIG_HIBERNATE_CALLBACKS */
Patches currently in stable-queue which might be from ross.lagerwall@xxxxxxxxxx are
queue-3.16/xen-manage-always-freeze-thaw-processes-when-suspend-resuming.patch
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