liveupdate: skip serialization for context-preserving kexec

A preserve_context kexec returns to the current kernel, which is
unrelated to live update where the state is passed to the next kernel.
Skip liveupdate_reboot() in this case to avoid serialization and prevent
sessions from being left in a frozen state upon return.

Fixes: db8bed8 ("kexec: call liveupdate_reboot() before kexec")
Reported-by: Oskar Gerlicz Kowalczuk <oskar@gerlicz.space>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260527202737.1345192-2-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

Author: soleen

kernel/kexec_core.c

@@ -1146,9 +1146,11 @@ int kernel_kexec(void)
 		goto Unlock;
 	}
 
-	error = liveupdate_reboot();
-	if (error)
-		goto Unlock;
+	if (!kexec_image->preserve_context) {
+		error = liveupdate_reboot();
+		if (error)
+			goto Unlock;
+	}
 
 #ifdef CONFIG_KEXEC_JUMP
 	if (kexec_image->preserve_context) {