rcu: Prevent initialization race in rcutorture kthreads (60f53782) · Commits · 戴 / test

When you do something like "t = kthread_run(...)", it is possible that the kthread will start running before the assignment to "t" happens. If the child kthread expects to find a pointer to its task_struct in "t", it will then be fatally disappointed. This commit therefore switches such cases to kthread_create() followed by wake_up_process(), guaranteeing that the assignment happens before the child kthread starts running. Reported-by:

Fengguang Wu <fengguang.wu@intel.com> Signed-off-by:

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

kernel/rcutorture.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -2029,7 +2029,7 @@ rcu_torture_init(void)
		/* Start up the kthreads. */

		VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
		writer_task = kthread_run(rcu_torture_writer, NULL,
		writer_task = kthread_create(rcu_torture_writer, NULL,
		"rcu_torture_writer");
		if (IS_ERR(writer_task)) {
		firsterr = PTR_ERR(writer_task);
		@@ -2037,6 +2037,7 @@ rcu_torture_init(void)
		writer_task = NULL;
		goto unwind;
		}
		wake_up_process(writer_task);
		fakewriter_tasks = kzalloc(nfakewriters * sizeof(fakewriter_tasks[0]),
		GFP_KERNEL);
		if (fakewriter_tasks == NULL) {
		@@ -2151,7 +2152,7 @@ rcu_torture_init(void)
		}
		if (shutdown_secs > 0) {
		shutdown_time = jiffies + shutdown_secs * HZ;
		shutdown_task = kthread_run(rcu_torture_shutdown, NULL,
		shutdown_task = kthread_create(rcu_torture_shutdown, NULL,
		"rcu_torture_shutdown");
		if (IS_ERR(shutdown_task)) {
		firsterr = PTR_ERR(shutdown_task);
		@@ -2159,6 +2160,7 @@ rcu_torture_init(void)
		shutdown_task = NULL;
		goto unwind;
		}
		wake_up_process(shutdown_task);
		}
		i = rcu_torture_onoff_init();
		if (i != 0) {

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