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Commit 85d678c0 authored by Bryan O'Donoghue's avatar Bryan O'Donoghue Committed by Greg Kroah-Hartman
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greybus: loopback: make loopback code thread safe 



Current code allows a sysfs callback and a kernel worker thread to write
all over and act upon data that could be in the process of being updated by
the other. This patch adds a reasonably coarse mutex to enscure sync
between the two.

Signed-off-by: default avatarBryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@google.com>
parent a7e60062

drivers/staging/greybus/loopback.c

+16 −4
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
 */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/kthread.h>

#include <linux/delay.h>
@@ -30,6 +31,7 @@ struct gb_loopback { 
	u8 version_major;

	u8 version_minor;



	struct mutex mutex;

	struct task_struct *task;

	wait_queue_head_t wq;
@@ -101,10 +103,13 @@ static ssize_t field##_store(struct device *dev, \ 
	struct gb_connection *connection = to_gb_connection(dev);	\

	struct gb_loopback *gb =					\

		(struct gb_loopback *)connection->private;		\

	mutex_lock(&gb->mutex);						\

	ret = sscanf(buf, "%"#type, &gb->field);			\

	if (ret != 1)							\

		return -EINVAL;						\

		len = -EINVAL;						\

	else								\

		gb_loopback_check_attr(gb);				\

	mutex_unlock(&gb->mutex);					\

	return len;							\

}									\

static DEVICE_ATTR_RW(field)
@@ -385,6 +390,7 @@ static void gb_loopback_calculate_stats(struct gb_loopback *gb) 
static int gb_loopback_fn(void *data)

{

	int error = 0;

	int ms_wait;

	struct gb_loopback *gb = (struct gb_loopback *)data;



	while (1) {
@@ -393,6 +399,8 @@ static int gb_loopback_fn(void *data) 
						 kthread_should_stop());

		if (kthread_should_stop())

			break;



		mutex_lock(&gb->mutex);

		if (gb->iteration_max) {

			if (gb->iteration_count < gb->iteration_max) {

				gb->iteration_count++;
@@ -400,6 +408,7 @@ static int gb_loopback_fn(void *data) 
					     "iteration_count");

			} else {

				gb->type = 0;

				mutex_unlock(&gb->mutex);

				continue;

			}

		}
@@ -412,8 +421,10 @@ static int gb_loopback_fn(void *data) 
		if (error)

			gb->error++;

		gb_loopback_calculate_stats(gb);

		if (gb->ms_wait)

			msleep(gb->ms_wait);

		ms_wait = gb->ms_wait;

		mutex_unlock(&gb->mutex);

		if (ms_wait)

			msleep(ms_wait);

	}

	return 0;

}
@@ -448,6 +459,7 @@ static int gb_loopback_connection_init(struct gb_connection *connection) 


	gb_loopback_reset_stats(gb);

	init_waitqueue_head(&gb->wq);

	mutex_init(&gb->mutex);

	gb->task = kthread_run(gb_loopback_fn, gb, "gb_loopback");

	if (IS_ERR(gb->task)) {

		retval = PTR_ERR(gb->task);