firmware: arm_sdei: Use cpus_read_lock() to avoid races with cpuhp (54f529a6) · Commits · 戴 / test

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>

drivers/firmware/arm_sdei.c

+14 −12

Original line number	Diff line number	Diff line
		@@ -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);

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