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

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>
This commit is contained in:
James Morse 2020-02-21 16:35:08 +00:00 committed by Catalin Marinas
parent c66d52b102
commit 54f529a680
1 changed files with 14 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
drivers/firmware/arm_sdei.c
View File

@ -418,14 +418,19 @@ 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;
@ -627,21 +632,18 @@ 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);