Fix rare deadlock on early xenbus device hotplug

0001-xen-xenbus-check-otherend_id-only-after-it-has-been-.patch

@@ -0,0 +1,46 @@
+From 00fcc430d3b5e9d1e4b4da3e8eccb4fe0eac7876 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
+ <marmarek@invisiblethingslab.com>
+Date: Sat, 1 Aug 2026 01:19:18 +0200
+Subject: [PATCH] xen/xenbus: check otherend_id only after it has been
+ initialized
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+When device just got initialized (for example on module load), the
+otherend_id field is initialized only after
+xenbus_read_otherend_details() gets called. If xenstore watch triggers
+xenbus_dev_changed() before that, it might consider still zeroed
+otherend_id field (not matching actual xenstore content) as a sign of
+device state reset. It can happen because xenstore watch are handled in
+another thread (xenwatch), which can run in parallel to the initial
+device probe running at module load. In that case, it would call
+device_unregister(), which would deadlock against device probe from
+module init.
+
+Fix this by considering dev->otherend_id change only after dev->otherend
+is set (which happen after otherend_id is initialized).
+
+Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
+---
+ drivers/xen/xenbus/xenbus_probe.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
+index a259c8f0fff4..b42d8d2e5a33 100644
+--- a/drivers/xen/xenbus/xenbus_probe.c
++++ b/drivers/xen/xenbus/xenbus_probe.c
+@@ -680,7 +680,8 @@ void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
+ 							    dev->otherend_id);
+
+ 		if (state == XenbusStateInitialising &&
+-		    (state != dev->state || backend != dev->otherend_id)) {
++		    (state != dev->state ||
++		     (dev->otherend && backend != dev->otherend_id))) {
+ 			/*
+ 			 * State has been reset, assume the old one vanished
+ 			 * and new one needs to be probed.
+-- 
+2.54.0
+

0001-xen-xenbus-log-more-information-when-device-state-go.patch

@@ -0,0 +1,33 @@
+From 2ee49295c56339e22ffdd7547a86a0c707cbcf23 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
+ <marmarek@invisiblethingslab.com>
+Date: Thu, 30 Jul 2026 16:11:49 +0200
+Subject: [PATCH] xen/xenbus: log more information when device state got reset
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Ease diagnosing what actually changed.
+
+Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
+---
+ drivers/xen/xenbus/xenbus_probe.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
+index eb260eceb4d2..a259c8f0fff4 100644
+--- a/drivers/xen/xenbus/xenbus_probe.c
++++ b/drivers/xen/xenbus/xenbus_probe.c
+@@ -686,7 +686,8 @@ void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
+ 			 * and new one needs to be probed.
+ 			 */
+ 			dev_warn(&dev->dev,
+-				 "state reset occurred, reconnecting\n");
++				 "state reset occurred (xenstore state %u, local state %u, xenstore backend %u, local backend %u), reconnecting\n",
++				 state, dev->state, backend, dev->otherend_id);
+ 			dev->vanished = true;
+ 		}
+ 		if (dev->vanished) {
+-- 
+2.54.0
+

kernel.spec.in

@@ -144,6 +144,8 @@ Patch27: 0001-amdgpu-timeout.patch
 Patch30: 0004-pvops-respect-removable-xenstore-flag-for-block-devi.patch
 Patch31: 0001-PCI-add-a-reset-quirk-for-Intel-I219LM-ethernet-adap.patch
 Patch34: 0001-rust-fixup.patch
+Patch35: 0001-xen-xenbus-log-more-information-when-device-state-go.patch
+Patch36: 0001-xen-xenbus-check-otherend_id-only-after-it-has-been-.patch
 
 # S0ix support:
 Patch61: xen-events-Add-wakeup-support-to-xen-pirq.patch