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greybus: loopback: make loopback code thread safe

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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: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Bryan O'Donoghue 2015-07-28 18:34:36 +01:00 committed by Greg Kroah-Hartman
parent a7e60062b0
commit 85d678c0be
1 changed files with 16 additions and 4 deletions
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20
drivers/staging/greybus/loopback.c
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@ -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; \
gb_loopback_check_attr(gb); \
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);