kernel/reboot: Fix powering off using a non-syscall code paths

There are other methods of powering off machine than the reboot syscall.
Previously we missed to cover those methods and it created power-off
regression for some machines, like the PowerPC e500.

Fix this problem by moving the legacy sys-off handler registration to
the latest phase of power-off process and making the kernel_can_power_off()
check the legacy pm_power_off presence.

Tested-by: Michael Ellerman <mpe@ellerman.id.au> # ppce500
Reported-by: Michael Ellerman <mpe@ellerman.id.au> # ppce500
Fixes: da007f171fc9 ("kernel/reboot: Change registration order of legacy power-off handler")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/reboot.c b/kernel/reboot.c
index 3b19b12..b5a71d1 100644 (file)
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -320,6 +320,7 @@ static struct sys_off_handler platform_sys_off_handler;
 static struct sys_off_handler *alloc_sys_off_handler(int priority)
 {
        struct sys_off_handler *handler;
+       gfp_t flags;
 
        /*
         * Platforms like m68k can't allocate sys_off handler dynamically
@@ -330,7 +331,12 @@ static struct sys_off_handler *alloc_sys_off_handler(int priority)
                if (handler->cb_data)
                        return ERR_PTR(-EBUSY);
        } else {
-               handler = kzalloc(sizeof(*handler), GFP_KERNEL);
+               if (system_state > SYSTEM_RUNNING)
+                       flags = GFP_ATOMIC;
+               else
+                       flags = GFP_KERNEL;
+
+               handler = kzalloc(sizeof(*handler), flags);
                if (!handler)
                        return ERR_PTR(-ENOMEM);
        }
@@ -440,7 +446,7 @@ void unregister_sys_off_handler(struct sys_off_handler *handler)
 {
        int err;
 
-       if (!handler)
+       if (IS_ERR_OR_NULL(handler))
                return;
 
        if (handler->blocking)
@@ -615,7 +621,23 @@ static void do_kernel_power_off_prepare(void)
  */
 void do_kernel_power_off(void)
 {
+       struct sys_off_handler *sys_off = NULL;
+
+       /*
+        * Register sys-off handlers for legacy PM callback. This allows
+        * legacy PM callbacks temporary co-exist with the new sys-off API.
+        *
+        * TODO: Remove legacy handlers once all legacy PM users will be
+        *       switched to the sys-off based APIs.
+        */
+       if (pm_power_off)
+               sys_off = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
+                                                  SYS_OFF_PRIO_DEFAULT,
+                                                  legacy_pm_power_off, NULL);
+
        atomic_notifier_call_chain(&power_off_handler_list, 0, NULL);
+
+       unregister_sys_off_handler(sys_off);
 }
 
 /**
@@ -626,7 +648,8 @@ void do_kernel_power_off(void)
  */
 bool kernel_can_power_off(void)
 {
-       return !atomic_notifier_call_chain_is_empty(&power_off_handler_list);
+       return !atomic_notifier_call_chain_is_empty(&power_off_handler_list) ||
+               pm_power_off;
 }
 EXPORT_SYMBOL_GPL(kernel_can_power_off);
 
@@ -661,7 +684,6 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
                void __user *, arg)
 {
        struct pid_namespace *pid_ns = task_active_pid_ns(current);
-       struct sys_off_handler *sys_off = NULL;
        char buffer[256];
        int ret = 0;
 
@@ -686,21 +708,6 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
        if (ret)
                return ret;
 
-       /*
-        * Register sys-off handlers for legacy PM callback. This allows
-        * legacy PM callbacks temporary co-exist with the new sys-off API.
-        *
-        * TODO: Remove legacy handlers once all legacy PM users will be
-        *       switched to the sys-off based APIs.
-        */
-       if (pm_power_off) {
-               sys_off = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
-                                                  SYS_OFF_PRIO_DEFAULT,
-                                                  legacy_pm_power_off, NULL);
-               if (IS_ERR(sys_off))
-                       return PTR_ERR(sys_off);
-       }
-
        /* Instead of trying to make the power_off code look like
         * halt when pm_power_off is not set do it the easy way.
         */
@@ -758,7 +765,6 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
                break;
        }
        mutex_unlock(&system_transition_mutex);
-       unregister_sys_off_handler(sys_off);
        return ret;
 }