firmware: arm_sdei: fix double-lock on hibernate with shared events

SDEI has private events that must be registered on each CPU. When
CPUs come and go they must re-register and re-enable their private
events. Each event has flags to indicate whether this should happen
to protect against an event being registered on a CPU coming online,
while all the others are unregistering the event.

These flags are protected by the sdei_list_lock spinlock, because
the cpuhp callbacks can't take the mutex.

Hibernate needs to unregister all events, but keep the in-memory
re-register and re-enable as they are. sdei_unregister_shared()
takes the spinlock to walk the list, then calls _sdei_event_unregister()
on each shared event. _sdei_event_unregister() tries to take the
same spinlock to update re-register and re-enable. This doesn't go
so well.

Push the re-register and re-enable updates out to their callers.
sdei_unregister_shared() doesn't want these values updated, so
doesn't need to do anything.

This also fixes shared events getting lost over hibernate as this
path made them look unregistered.

Fixes: da351827240e ("firmware: arm_sdei: Add support for CPU and system power states")
Reported-by: Liguang Zhang <zhangliguang@linux.alibaba.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index a479023fa036ebdf15d1785a8f2005e70e8231a4..77eaa9a2fd15627cc0e09b52fda7922bba0f0ad8 100644 (file)
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -491,11 +491,6 @@ static int _sdei_event_unregister(struct sdei_event *event)
 {
        lockdep_assert_held(&sdei_events_lock);
 
-       spin_lock(&sdei_list_lock);
-       event->reregister = false;
-       event->reenable = false;
-       spin_unlock(&sdei_list_lock);
-
        if (event->type == SDEI_EVENT_TYPE_SHARED)
                return sdei_api_event_unregister(event->event_num);
 
@@ -518,6 +513,11 @@ int sdei_event_unregister(u32 event_num)
                        break;
                }
 
+               spin_lock(&sdei_list_lock);
+               event->reregister = false;
+               event->reenable = false;
+               spin_unlock(&sdei_list_lock);
+
                err = _sdei_event_unregister(event);
                if (err)
                        break;
@@ -585,26 +585,15 @@ static int _sdei_event_register(struct sdei_event *event)
 
        lockdep_assert_held(&sdei_events_lock);
 
-       spin_lock(&sdei_list_lock);
-       event->reregister = true;
-       spin_unlock(&sdei_list_lock);
-
        if (event->type == SDEI_EVENT_TYPE_SHARED)
                return sdei_api_event_register(event->event_num,
                                               sdei_entry_point,
                                               event->registered,
                                               SDEI_EVENT_REGISTER_RM_ANY, 0);
 
-
        err = sdei_do_cross_call(_local_event_register, event);
-       if (err) {
-               spin_lock(&sdei_list_lock);
-               event->reregister = false;
-               event->reenable = false;
-               spin_unlock(&sdei_list_lock);
-
+       if (err)
                sdei_do_cross_call(_local_event_unregister, event);
-       }
 
        return err;
 }
@@ -632,8 +621,17 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
                        break;
                }
 
+               spin_lock(&sdei_list_lock);
+               event->reregister = true;
+               spin_unlock(&sdei_list_lock);
+
                err = _sdei_event_register(event);
                if (err) {
+                       spin_lock(&sdei_list_lock);
+                       event->reregister = false;
+                       event->reenable = false;
+                       spin_unlock(&sdei_list_lock);
+
                        sdei_event_destroy(event);
                        pr_warn("Failed to register event %u: %d\n", event_num,
                                err);