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Commit da573eaa authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Jon Mason
Browse files

ntb_perf: Improve thread handling to increase robustness 



This commit accomplishes a few things:

1) Properly prevent multiple sets of threads from running at once using
a mutex. Lots of race issues existed with the thread_cleanup.

2) The mutex allows us to ensure that threads are finished before
tearing down the device or module.

3) Don't use kthread_stop when the threads can exit by themselves, as
this is counter-indicated by the kthread_create documentation. Threads
now wait for kthread_stop to occur.

4) Writing to the run file now blocks until the threads are complete.
The test can then be safely interrupted by a SIGINT.

Also, while I was at it:

5) debugfs_run_write shouldn't return 0 in the early check cases as this
could cause debugfs_run_write to loop undesirably.

Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Acked-by: default avatarDave Jiang <dave.jiang@intel.com>
Signed-off-by: default avatarJon Mason <jdmason@kudzu.us>
parent fd2ecd88

drivers/ntb/test/ntb_perf.c

+76 −48
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ 
#include <linux/delay.h>

#include <linux/sizes.h>

#include <linux/ntb.h>

#include <linux/mutex.h>



#define DRIVER_NAME		"ntb_perf"

#define DRIVER_DESCRIPTION	"PCIe NTB Performance Measurement Tool"
@@ -121,6 +122,7 @@ struct pthr_ctx { 
	int			dma_prep_err;

	int			src_idx;

	void			*srcs[MAX_SRCS];

	wait_queue_head_t       *wq;

};



struct perf_ctx {
@@ -134,9 +136,11 @@ struct perf_ctx { 
	struct dentry		*debugfs_run;

	struct dentry		*debugfs_threads;

	u8			perf_threads;

	bool			run;

	/* mutex ensures only one set of threads run at once */

	struct mutex		run_mutex;

	struct pthr_ctx		pthr_ctx[MAX_THREADS];

	atomic_t		tsync;

	atomic_t                tdone;

};



enum {
@@ -295,13 +299,19 @@ static int perf_move_data(struct pthr_ctx *pctx, char __iomem *dst, char *src, 
			set_current_state(TASK_INTERRUPTIBLE);

			schedule_timeout(1);

		}



		if (unlikely(kthread_should_stop()))

			break;

	}



	if (use_dma) {

		pr_info("%s: All DMA descriptors submitted\n", current->comm);

		while (atomic_read(&pctx->dma_sync) != 0)

		while (atomic_read(&pctx->dma_sync) != 0) {

			if (kthread_should_stop())

				break;

			msleep(20);

		}

	}



	kstop = ktime_get();

	kdiff = ktime_sub(kstop, kstart);
@@ -393,7 +403,10 @@ static int ntb_perf_thread(void *data) 
		pctx->srcs[i] = NULL;

	}



	return 0;

	atomic_inc(&perf->tdone);

	wake_up(pctx->wq);

	rc = 0;

	goto done;



err:

	for (i = 0; i < MAX_SRCS; i++) {
@@ -406,6 +419,16 @@ static int ntb_perf_thread(void *data) 
		pctx->dma_chan = NULL;

	}



done:

	/* Wait until we are told to stop */

	for (;;) {

		set_current_state(TASK_INTERRUPTIBLE);

		if (kthread_should_stop())

			break;

		schedule();

	}

	__set_current_state(TASK_RUNNING);



	return rc;

}
@@ -553,6 +576,7 @@ static ssize_t debugfs_run_read(struct file *filp, char __user *ubuf, 
	struct perf_ctx *perf = filp->private_data;

	char *buf;

	ssize_t ret, out_offset;

	int running;



	if (!perf)

		return 0;
@@ -560,7 +584,9 @@ static ssize_t debugfs_run_read(struct file *filp, char __user *ubuf, 
	buf = kmalloc(64, GFP_KERNEL);

	if (!buf)

		return -ENOMEM;

	out_offset = snprintf(buf, 64, "%d\n", perf->run);



	running = mutex_is_locked(&perf->run_mutex);

	out_offset = snprintf(buf, 64, "%d\n", running);

	ret = simple_read_from_buffer(ubuf, count, offp, buf, out_offset);

	kfree(buf);
@@ -572,7 +598,6 @@ static void threads_cleanup(struct perf_ctx *perf) 
	struct pthr_ctx *pctx;

	int i;



	perf->run = false;

	for (i = 0; i < MAX_THREADS; i++) {

		pctx = &perf->pthr_ctx[i];

		if (pctx->thread) {
@@ -587,20 +612,16 @@ static ssize_t debugfs_run_write(struct file *filp, const char __user *ubuf, 
{

	struct perf_ctx *perf = filp->private_data;

	int node, i;

	DECLARE_WAIT_QUEUE_HEAD(wq);



	if (!perf->link_is_up)

		return 0;

		return -ENOLINK;



	if (perf->perf_threads == 0)

		return 0;



	if (atomic_read(&perf->tsync) == 0)

		perf->run = false;

		return -EINVAL;



	if (perf->run)

		threads_cleanup(perf);

	else {

		perf->run = true;

	if (!mutex_trylock(&perf->run_mutex))

		return -EBUSY;



	if (perf->perf_threads > MAX_THREADS) {

		perf->perf_threads = MAX_THREADS;
@@ -619,6 +640,8 @@ static ssize_t debugfs_run_write(struct file *filp, const char __user *ubuf, 
	}



	node = dev_to_node(&perf->ntb->pdev->dev);

	atomic_set(&perf->tdone, 0);



	/* launch kernel thread */

	for (i = 0; i < perf->perf_threads; i++) {

		struct pthr_ctx *pctx;
@@ -626,6 +649,7 @@ static ssize_t debugfs_run_write(struct file *filp, const char __user *ubuf, 
		pctx = &perf->pthr_ctx[i];

		atomic_set(&pctx->dma_sync, 0);

		pctx->perf = perf;

		pctx->wq = &wq;

		pctx->thread =

			kthread_create_on_node(ntb_perf_thread,

					       (void *)pctx,
@@ -633,19 +657,21 @@ static ssize_t debugfs_run_write(struct file *filp, const char __user *ubuf, 
		if (IS_ERR(pctx->thread)) {

			pctx->thread = NULL;

			goto err;

			} else

		} else {

			wake_up_process(pctx->thread);



			if (perf->run == false)

				return -ENXIO;

		}



	}



	wait_event_interruptible(wq,

		atomic_read(&perf->tdone) == perf->perf_threads);



	threads_cleanup(perf);

	mutex_unlock(&perf->run_mutex);

	return count;



err:

	threads_cleanup(perf);

	mutex_unlock(&perf->run_mutex);

	return -ENXIO;

}
@@ -713,7 +739,7 @@ static int perf_probe(struct ntb_client *client, struct ntb_dev *ntb) 
	perf->ntb = ntb;

	perf->perf_threads = 1;

	atomic_set(&perf->tsync, 0);

	perf->run = false;

	mutex_init(&perf->run_mutex);

	spin_lock_init(&perf->db_lock);

	perf_setup_mw(ntb, perf);

	INIT_DELAYED_WORK(&perf->link_work, perf_link_work);
@@ -748,6 +774,8 @@ static void perf_remove(struct ntb_client *client, struct ntb_dev *ntb) 


	dev_dbg(&perf->ntb->dev, "%s called\n", __func__);



	mutex_lock(&perf->run_mutex);



	cancel_delayed_work_sync(&perf->link_work);

	cancel_work_sync(&perf->link_cleanup);