dmatest: add a 'wait' parameter

Allows for scripting test runs by module load / unload. Prevent module
load from returning until 'iterations' (finite) tests have completed, or
cause reads of the 'wait' parameter in sysfs to pause until the tests
are done.

Also killed the local waitqueue since we can just let the thread exit
naturally as long as we hold a reference.

Cc: Nicolas Ferre <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

Documentation/dmatest.txt

···
 
 Note that running a new test will not stop any in progress test.
 
-The following command should return actual state of the test.
-	% cat /sys/kernel/debug/dmatest/run
+The following command returns the state of the test.
+	% cat /sys/module/dmatest/parameters/run
 
-To wait for test done the user may perform a busy loop that checks the state.
+To wait for test completion userpace can poll 'run' until it is false, or use
+the wait parameter.  Specifying 'wait=1' when loading the module causes module
+initialization to pause until a test run has completed, while reading
+/sys/module/dmatest/parameters/wait waits for any running test to complete
+before returning.  For example, the following scripts wait for 42 tests
+to complete before exiting.  Note that if 'iterations' is set to 'infinite' then
+waiting is disabled.
 
-	% while [ $(cat /sys/module/dmatest/parameters/run) = "Y" ]
-	> do
-	> 	echo -n "."
-	> 	sleep 1
-	> done
-	> echo
+Example:
+	% modprobe dmatest run=1 iterations=42 wait=1
+	% modprobe -r dmatest
+...or:
+	% modprobe dmatest run=1 iterations=42
+	% cat /sys/module/dmatest/parameters/wait
+	% modprobe -r dmatest
 
 	Part 3 - When built-in in the kernel...
 
···
 
 Example:
 	% dmesg | tail -n 1
-	dmatest: dma3chan0-copy0: summary 400000 tests, 0 failures iops: 61524 KB/s 246098 (0)
+	dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
 
 The details of a data miscompare error are also emitted, but do not follow the
 above format.

drivers/dma/dmatest.c

···
 	struct list_head	threads;
 };
 
+static DECLARE_WAIT_QUEUE_HEAD(thread_wait);
+static bool wait;
+
+static bool is_threaded_test_run(struct dmatest_info *info)
+{
+	struct dmatest_chan *dtc;
+
+	list_for_each_entry(dtc, &info->channels, node) {
+		struct dmatest_thread *thread;
+
+		list_for_each_entry(thread, &dtc->threads, node) {
+			if (!thread->done)
+				return true;
+		}
+	}
+
+	return false;
+}
+
+static int dmatest_wait_get(char *val, const struct kernel_param *kp)
+{
+	struct dmatest_info *info = &test_info;
+	struct dmatest_params *params = &info->params;
+
+	if (params->iterations)
+		wait_event(thread_wait, !is_threaded_test_run(info));
+	wait = true;
+	return param_get_bool(val, kp);
+}
+
+static struct kernel_param_ops wait_ops = {
+	.get = dmatest_wait_get,
+	.set = param_set_bool,
+};
+module_param_cb(wait, &wait_ops, &wait, S_IRUGO);
+MODULE_PARM_DESC(wait, "Wait for tests to complete (default: false)");
+
 static bool dmatest_match_channel(struct dmatest_params *params,
 		struct dma_chan *chan)
 {
···
 		dmaengine_terminate_all(chan);
 
 	thread->done = true;
-
-	if (params->iterations > 0)
-		while (!kthread_should_stop()) {
-			DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wait_dmatest_exit);
-			interruptible_sleep_on(&wait_dmatest_exit);
-		}
+	wake_up(&thread_wait);
 
 	return ret;
 }
···
 		pr_debug("thread %s exited with status %d\n",
 			 thread->task->comm, ret);
 		list_del(&thread->node);
+		put_task_struct(thread->task);
 		kfree(thread);
 	}
 
···
 		thread->chan = dtc->chan;
 		thread->type = type;
 		smp_wmb();
-		thread->task = kthread_run(dmatest_func, thread, "%s-%s%u",
+		thread->task = kthread_create(dmatest_func, thread, "%s-%s%u",
 				dma_chan_name(chan), op, i);
 		if (IS_ERR(thread->task)) {
-			pr_warn("Failed to run thread %s-%s%u\n",
+			pr_warn("Failed to create thread %s-%s%u\n",
 				dma_chan_name(chan), op, i);
 			kfree(thread);
 			break;
 		}
 
 		/* srcbuf and dstbuf are allocated by the thread itself */
-
+		get_task_struct(thread->task);
 		list_add_tail(&thread->node, &dtc->threads);
+		wake_up_process(thread->task);
 	}
 
 	return i;
···
 	run_threaded_test(info);
 }
 
-static bool is_threaded_test_run(struct dmatest_info *info)
-{
-	struct dmatest_chan *dtc;
-
-	list_for_each_entry(dtc, &info->channels, node) {
-		struct dmatest_thread *thread;
-
-		list_for_each_entry(thread, &dtc->threads, node) {
-			if (!thread->done)
-				return true;
-		}
-	}
-
-	return false;
-}
-
 static int dmatest_run_get(char *val, const struct kernel_param *kp)
 {
 	struct dmatest_info *info = &test_info;
···
 static int __init dmatest_init(void)
 {
 	struct dmatest_info *info = &test_info;
+	struct dmatest_params *params = &info->params;
 
 	if (dmatest_run) {
 		mutex_lock(&info->lock);
 		run_threaded_test(info);
 		mutex_unlock(&info->lock);
 	}
+
+	if (params->iterations && wait)
+		wait_event(thread_wait, !is_threaded_test_run(info));
 
 	/* module parameters are stable, inittime tests are started,
 	 * let userspace take over 'run' control