[PATCH AUTOSEL 5.6 10/68] firmware: arm_sdei: fix double-lock on hibernate with shared events

Sasha Levin
2020-04-10T04:03:16Z

From: James Morse <james.morse@arm.com>

[ Upstream commit 6ded0b61cf638bf9f8efe60ab8ba23db60ea9763 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/firmware/arm_sdei.c | 32 +++++++++++++++-----------------
1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index a479023fa036e..77eaa9a2fd156 100644
--- 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);
--
2.20.1