Xen's do_suspend() calls dpm_suspend_start() without taking required
system_transition_mutex. Since 12ffc3b1513eb moved the
pm_restrict_gfp_mask() call, not taking that mutex results in a WARN.

Take the mutex in do_suspend(), and use mutex_trylock() to follow
how enter_state() does this.

Suggested-by: Jürgen Groß <jgross@suse.com>
Fixes: 12ffc3b1513eb "PM: Restrict swap use to later in the suspend sequence"
Link: https://lore.kernel.org/xen-devel/aKiBJeqsYx_4Top5@mail-itl/
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Cc: stable@vger.kernel.org # v6.16+
---
 drivers/xen/manage.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index b4b4ebed68daf..f78d970949c0a 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -11,6 +11,7 @@
 #include <linux/reboot.h>
 #include <linux/sysrq.h>
 #include <linux/stop_machine.h>
+#include <linux/suspend.h>
 #include <linux/freezer.h>
 #include <linux/syscore_ops.h>
 #include <linux/export.h>
@@ -101,10 +102,16 @@ static void do_suspend(void)
 
 	shutting_down = SHUTDOWN_SUSPEND;
 
+	if (!mutex_trylock(&system_transition_mutex))
+	{
+		pr_err("%s: failed to take system_transition_mutex\n", __func__);
+		goto out;
+	}
+
 	err = freeze_processes();
 	if (err) {
 		pr_err("%s: freeze processes failed %d\n", __func__, err);
-		goto out;
+		goto out_unlock;
 	}
 
 	err = freeze_kernel_threads();
@@ -160,6 +167,8 @@ static void do_suspend(void)
 
 out_thaw:
 	thaw_processes();
+out_unlock:
+	mutex_unlock(&system_transition_mutex);
 out:
 	shutting_down = SHUTDOWN_INVALID;
 }
-- 
2.51.0

On 21.09.25 18:28, Marek Marczykowski-Górecki wrote:
> Xen's do_suspend() calls dpm_suspend_start() without taking required
> system_transition_mutex. Since 12ffc3b1513eb moved the
> pm_restrict_gfp_mask() call, not taking that mutex results in a WARN.
> 
> Take the mutex in do_suspend(), and use mutex_trylock() to follow
> how enter_state() does this.
> 
> Suggested-by: Jürgen Groß <jgross@suse.com>
> Fixes: 12ffc3b1513eb "PM: Restrict swap use to later in the suspend sequence"
> Link: https://lore.kernel.org/xen-devel/aKiBJeqsYx_4Top5@mail-itl/
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> Cc: stable@vger.kernel.org # v6.16+

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

On 9/22/25 1:06 AM, Jürgen Groß wrote:
> On 21.09.25 18:28, Marek Marczykowski-Górecki wrote:
>> Xen's do_suspend() calls dpm_suspend_start() without taking required
>> system_transition_mutex. Since 12ffc3b1513eb moved the
>> pm_restrict_gfp_mask() call, not taking that mutex results in a WARN.
>>
>> Take the mutex in do_suspend(), and use mutex_trylock() to follow
>> how enter_state() does this.
>>
>> Suggested-by: Jürgen Groß <jgross@suse.com>
>> Fixes: 12ffc3b1513eb "PM: Restrict swap use to later in the suspend 
>> sequence"
>> Link: https://lore.kernel.org/xen-devel/aKiBJeqsYx_4Top5@mail-itl/
>> Signed-off-by: Marek Marczykowski-Górecki 
>> <marmarek@invisiblethingslab.com>
>> Cc: stable@vger.kernel.org # v6.16+
> 
> Reviewed-by: Juergen Gross <jgross@suse.com>
> 
> 
> Juergen

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>