Merge "hotplugcpu: Avoid deadlocks by waking active_writer" (0c132bc0) · Commits · e / devices / android_kernel_xiaomi_markw

kernel/cpu.c

+24 −27

Original line number	Diff line number	Diff line
		@@ -60,22 +60,23 @@ static int cpu_hotplug_disabled;

		static struct {
		struct task_struct *active_writer;
		struct mutex lock; /* Synchronizes accesses to refcount, */
		/* wait queue to wake up the active_writer */
		wait_queue_head_t wq;
		/* verifies that no writer will get active while readers are active */
		struct mutex lock;
		/*
		* Also blocks the new readers during
		* an ongoing cpu hotplug operation.
		*/
		int refcount;
		/* And allows lockless put_online_cpus(). */
		atomic_t puts_pending;
		atomic_t refcount;

		#ifdef CONFIG_DEBUG_LOCK_ALLOC
		struct lockdep_map dep_map;
		#endif
		} cpu_hotplug = {
		.active_writer = NULL,
		.wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
		.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
		.refcount = 0,
		#ifdef CONFIG_DEBUG_LOCK_ALLOC
		.dep_map = {.name = "cpu_hotplug.lock" },
		#endif
		@@ -88,6 +89,7 @@ static struct {
		#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
		#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)


		void get_online_cpus(void)
		{
		might_sleep();
		@@ -95,7 +97,7 @@ void get_online_cpus(void)
		return;
		cpuhp_lock_acquire_read();
		mutex_lock(&cpu_hotplug.lock);
		cpu_hotplug.refcount++;
		atomic_inc(&cpu_hotplug.refcount);
		mutex_unlock(&cpu_hotplug.lock);
		}
		EXPORT_SYMBOL_GPL(get_online_cpus);
		@@ -107,7 +109,7 @@ bool try_get_online_cpus(void)
		if (!mutex_trylock(&cpu_hotplug.lock))
		return false;
		cpuhp_lock_acquire_tryread();
		cpu_hotplug.refcount++;
		atomic_inc(&cpu_hotplug.refcount);
		mutex_unlock(&cpu_hotplug.lock);
		return true;
		}
		@@ -115,20 +117,18 @@ EXPORT_SYMBOL_GPL(try_get_online_cpus);

		void put_online_cpus(void)
		{
		int refcount;

		if (cpu_hotplug.active_writer == current)
		return;
		if (!mutex_trylock(&cpu_hotplug.lock)) {
		atomic_inc(&cpu_hotplug.puts_pending);
		cpuhp_lock_release();
		return;
		}

		if (WARN_ON(!cpu_hotplug.refcount))
		cpu_hotplug.refcount++; /* try to fix things up */
		refcount = atomic_dec_return(&cpu_hotplug.refcount);
		if (WARN_ON(refcount < 0)) /* try to fix things up */
		atomic_inc(&cpu_hotplug.refcount);

		if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
		wake_up(&cpu_hotplug.wq);

		if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
		wake_up_process(cpu_hotplug.active_writer);
		mutex_unlock(&cpu_hotplug.lock);
		cpuhp_lock_release();

		}
		@@ -158,23 +158,20 @@ EXPORT_SYMBOL_GPL(put_online_cpus);
		*/
		void cpu_hotplug_begin(void)
		{
		cpu_hotplug.active_writer = current;
		DEFINE_WAIT(wait);

		cpu_hotplug.active_writer = current;
		cpuhp_lock_acquire();

		for (;;) {
		mutex_lock(&cpu_hotplug.lock);
		if (atomic_read(&cpu_hotplug.puts_pending)) {
		int delta;

		delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
		cpu_hotplug.refcount -= delta;
		}
		if (likely(!cpu_hotplug.refcount))
		prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
		if (likely(!atomic_read(&cpu_hotplug.refcount)))
		break;
		__set_current_state(TASK_UNINTERRUPTIBLE);
		mutex_unlock(&cpu_hotplug.lock);
		schedule();
		}
		finish_wait(&cpu_hotplug.wq, &wait);
		}

		void cpu_hotplug_done(void)