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firmware: arm_sdei: Use cpus_read_lock() to avoid races with cpuhp

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[ Upstream commit 54f529a680 ]

SDEI has private events that need registering and enabling on each CPU.
CPUs can come and go while we are trying to do this. SDEI tries to avoid
these problems by setting the reregister flag before the register call,
so any CPUs that come online register the event too. Sticking plaster
like this doesn't work, as if the register call fails, a CPU that
subsequently comes online will register the event before reregister
is cleared.

Take cpus_read_lock() around the register and enable calls. We don't
want surprise CPUs to do the wrong thing if they race with these calls
failing.

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>
This commit is contained in:
James Morse 2020-02-21 16:35:08 +00:00 committed by Greg Kroah-Hartman
parent 21e2f6bf08
commit 1edfaecc30
1 changed files with 14 additions and 12 deletions
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26
drivers/firmware/arm_sdei.c
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@ -412,14 +412,19 @@ int sdei_event_enable(u32 event_num)
return -ENOENT;
}
spin_lock(&sdei_list_lock);
event->reenable = true;
spin_unlock(&sdei_list_lock);
cpus_read_lock();
if (event->type == SDEI_EVENT_TYPE_SHARED)
err = sdei_api_event_enable(event->event_num);
else
err = sdei_do_cross_call(_local_event_enable, event);
if (!err) {
spin_lock(&sdei_list_lock);
event->reenable = true;
spin_unlock(&sdei_list_lock);
}
cpus_read_unlock();
mutex_unlock(&sdei_events_lock);
return err;
@ -621,21 +626,18 @@ 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);
cpus_read_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);
} else {
spin_lock(&sdei_list_lock);
event->reregister = true;
spin_unlock(&sdei_list_lock);
}
cpus_read_unlock();
} while (0);
mutex_unlock(&sdei_events_lock);