rcutorture: Adjust number of reader kthreads per CPU-hotplug operations (c04dd09b) · Commits · 戴 / test

Currently, rcutorture provisions rcu_torture_reader() kthreads based on the initial number of CPUs. This can be problematic when CPU hotplug is enabled, as a system with a very large number of CPUs will provision a very large number of rcu_torture_reader() kthreads. All of these kthreads will continue running even if the CPU-hotplug operations result in only one remaining online CPU. This can result in all sorts of strange artifacts due simply to massive overload. This commit therefore causes the rcu_torture_reader() kthreads to start blocking as the number of online CPUs decreases. This is accomplished by numbering these kthreads, and having each check to make sure that the number of online CPUs is at least as large as its assigned number. Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/rcutorture.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1400,6 +1400,8 @@ static int
		rcu_torture_reader(void *arg)
		{
		unsigned long lastsleep = jiffies;
		long myid = (long)arg;
		int mynumonline = myid;
		DEFINE_TORTURE_RANDOM(rand);
		struct timer_list t;

		@@ -1419,6 +1421,8 @@ rcu_torture_reader(void *arg)
		schedule_timeout_interruptible(1);
		lastsleep = jiffies + 10;
		}
		while (num_online_cpus() < mynumonline && !torture_must_stop())
		schedule_timeout_interruptible(HZ / 5);
		stutter_wait("rcu_torture_reader");
		} while (!torture_must_stop());
		if (irqreader && cur_ops->irq_capable) {
		@@ -2063,7 +2067,7 @@ static void rcu_test_debug_objects(void)
		static int __init
		rcu_torture_init(void)
		{
		int i;
		long i;
		int cpu;
		int firsterr = 0;
		static struct rcu_torture_ops *torture_ops[] = {
		@@ -2169,7 +2173,7 @@ rcu_torture_init(void)
		goto unwind;
		}
		for (i = 0; i < nrealreaders; i++) {
		firsterr = torture_create_kthread(rcu_torture_reader, NULL,
		firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
		reader_tasks[i]);
		if (firsterr)
		goto unwind;

Admin message