Date: Wed,  6 Sep 2023 12:47:53 +0200
From: Xabier Marquiegui <reibax@...il.com>
To: richardcochran@...il.com
Cc: chrony-dev@...ony.tuxfamily.org,
	mlichvar@...hat.com,
	netdev@...r.kernel.org,
	ntp-lists@...tcorallo.com,
	reibax@...il.com
Subject: [PATCH 2/3] ptp: support multiple timestamp event readers

Use linked lists to create one event queue per open file. This enables
simultaneous readers for timestamp event queues.

Signed-off-by: Xabier Marquiegui <reibax@...il.com>
---
 drivers/ptp/ptp_chardev.c | 95 ++++++++++++++++++++++++++++++---------
 drivers/ptp/ptp_clock.c   |  6 +--
 drivers/ptp/ptp_private.h |  4 +-
 drivers/ptp/ptp_sysfs.c   |  4 --
 4 files changed, 80 insertions(+), 29 deletions(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 1ea11f864abb..c65dc6fefaa6 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -103,9 +103,39 @@ int ptp_set_pinfunc(struct ptp_clock *ptp, unsigned int pin,
 
 int ptp_open(struct posix_clock *pc, fmode_t fmode)
 {
+	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+	struct timestamp_event_queue *queue;
+
+	queue = kzalloc(sizeof(struct timestamp_event_queue), GFP_KERNEL);
+	if (queue == NULL)
+		return -EINVAL;
+	queue->reader_pid = task_pid_nr(current);
+	list_add_tail(&queue->qlist, &ptp->tsevqs);
+
 	return 0;
 }
 
+int ptp_release(struct posix_clock *pc)
+{
+	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
+	struct list_head *pos, *n;
+	struct timestamp_event_queue *element;
+	int found = -1;
+	pid_t reader_pid = task_pid_nr(current);
+
+	list_for_each_safe(pos, n, &ptp->tsevqs) {
+		element = list_entry(pos, struct timestamp_event_queue, qlist);
+		if (element->reader_pid == reader_pid) {
+			list_del(pos);
+			kfree(element);
+			found = 0;
+			return found;
+		}
+	}
+
+	return found;
+}
+
 long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
 {
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
@@ -436,14 +466,25 @@ __poll_t ptp_poll(struct posix_clock *pc, struct file *fp, poll_table *wait)
 {
 	struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
 	struct timestamp_event_queue *queue;
+	struct list_head *pos, *n;
+	bool found = false;
+	pid_t reader_pid = task_pid_nr(current);
 
 	poll_wait(fp, &ptp->tsev_wq, wait);
 
 	/*
-	 * Extract only the first element in the queue list
-	 * TODO: Identify the relevant queue
+	 * Extract only the desired element in the queue list
 	 */
-	queue = list_entry(&ptp->tsevqs, struct timestamp_event_queue, qlist);
+	list_for_each_safe(pos, n, &ptp->tsevqs) {
+		queue = list_entry(pos, struct timestamp_event_queue, qlist);
+		if (queue->reader_pid == reader_pid) {
+			found = true;
+			break;
+		}
+	}
+
+	if (!found)
+		return -EINVAL;
 
 	return queue_cnt(queue) ? EPOLLIN : 0;
 }
@@ -459,40 +500,50 @@ ssize_t ptp_read(struct posix_clock *pc,
 	unsigned long flags;
 	size_t qcnt, i;
 	int result;
+	struct list_head *pos, *n;
+	bool found = false;
+	pid_t reader_pid = task_pid_nr(current);
 
 	/*
-	 * Extract only the first element in the queue list
-	 * TODO: Identify the relevant queue
+	 * Extract only the desired element in the queue list
 	 */
-	queue = list_first_entry(&ptp->tsevqs, struct timestamp_event_queue,
-				 qlist);
+	list_for_each_safe(pos, n, &ptp->tsevqs) {
+		queue = list_entry(pos, struct timestamp_event_queue, qlist);
+		if (queue->reader_pid == reader_pid) {
+			found = true;
+			break;
+		}
+	}
 
-	if (cnt % sizeof(struct ptp_extts_event) != 0)
-		return -EINVAL;
+	if (!found) {
+		result = -EINVAL;
+		goto exit;
+	}
+
+	if (cnt % sizeof(struct ptp_extts_event) != 0) {
+		result = -EINVAL;
+		goto exit;
+	}
 
 	if (cnt > EXTTS_BUFSIZE)
 		cnt = EXTTS_BUFSIZE;
 
 	cnt = cnt / sizeof(struct ptp_extts_event);
 
-	if (mutex_lock_interruptible(&ptp->tsevq_mux))
-		return -ERESTARTSYS;
-
 	if (wait_event_interruptible(ptp->tsev_wq,
 				     ptp->defunct || queue_cnt(queue))) {
-		mutex_unlock(&ptp->tsevq_mux);
 		return -ERESTARTSYS;
 	}
 
 	if (ptp->defunct) {
-		mutex_unlock(&ptp->tsevq_mux);
-		return -ENODEV;
+		result = -ENODEV;
+		goto exit;
 	}
 
 	event = kmalloc(EXTTS_BUFSIZE, GFP_KERNEL);
 	if (!event) {
-		mutex_unlock(&ptp->tsevq_mux);
-		return -ENOMEM;
+		result = -ENOMEM;
+		goto exit;
 	}
 
 	spin_lock_irqsave(&queue->lock, flags);
@@ -511,12 +562,16 @@ ssize_t ptp_read(struct posix_clock *pc,
 
 	cnt = cnt * sizeof(struct ptp_extts_event);
 
-	mutex_unlock(&ptp->tsevq_mux);
-
 	result = cnt;
-	if (copy_to_user(buf, event, cnt))
+	if (copy_to_user(buf, event, cnt)) {
 		result = -EFAULT;
+		goto free_event;
+	}
 
+free_event:
 	kfree(event);
+exit:
+	if (result < 0)
+		ptp_release(pc);
 	return result;
 }
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
index dd48b9f41535..dc2f045cacbd 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -162,6 +162,7 @@ static struct posix_clock_operations ptp_clock_ops = {
 	.clock_settime	= ptp_clock_settime,
 	.ioctl		= ptp_ioctl,
 	.open		= ptp_open,
+	.release	= ptp_release,
 	.poll		= ptp_poll,
 	.read		= ptp_read,
 };
@@ -184,7 +185,6 @@ static void ptp_clock_release(struct device *dev)
 
 	ptp_cleanup_pin_groups(ptp);
 	kfree(ptp->vclock_index);
-	mutex_destroy(&ptp->tsevq_mux);
 	mutex_destroy(&ptp->pincfg_mux);
 	mutex_destroy(&ptp->n_vclocks_mux);
 	ptp_clean_queue_list(ptp);
@@ -246,10 +246,9 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	queue = kzalloc(sizeof(struct timestamp_event_queue), GFP_KERNEL);
 	if (queue == NULL)
 		goto no_memory_queue;
+	queue->reader_pid = 0;
 	spin_lock_init(&queue->lock);
 	list_add_tail(&queue->qlist, &ptp->tsevqs);
-	/* TODO - Transform or delete this mutex */
-	mutex_init(&ptp->tsevq_mux);
 	mutex_init(&ptp->pincfg_mux);
 	mutex_init(&ptp->n_vclocks_mux);
 	init_waitqueue_head(&ptp->tsev_wq);
@@ -350,7 +349,6 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	if (ptp->kworker)
 		kthread_destroy_worker(ptp->kworker);
 kworker_err:
-	mutex_destroy(&ptp->tsevq_mux);
 	mutex_destroy(&ptp->pincfg_mux);
 	mutex_destroy(&ptp->n_vclocks_mux);
 	ptp_clean_queue_list(ptp);
diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
index 014293255677..56b0c9df188d 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h
@@ -27,6 +27,7 @@ struct timestamp_event_queue {
 	int tail;
 	spinlock_t lock;
 	struct list_head qlist; /* Link to other queues */
+	pid_t reader_pid;
 };
 
 struct ptp_clock {
@@ -38,7 +39,6 @@ struct ptp_clock {
 	struct pps_device *pps_source;
 	long dialed_frequency; /* remembers the frequency adjustment */
 	struct list_head tsevqs; /* timestamp fifo list */
-	struct mutex tsevq_mux; /* one process at a time reading the fifo */
 	struct mutex pincfg_mux; /* protect concurrent info->pin_config access */
 	wait_queue_head_t tsev_wq;
 	int defunct; /* tells readers to go away when clock is being removed */
@@ -124,6 +124,8 @@ long ptp_ioctl(struct posix_clock *pc,
 
 int ptp_open(struct posix_clock *pc, fmode_t fmode);
 
+int ptp_release(struct posix_clock *pc);
+
 ssize_t ptp_read(struct posix_clock *pc,
 		 uint flags, char __user *buf, size_t cnt);
 
diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c
index 2675f383cd0a..512b0164ef18 100644
--- a/drivers/ptp/ptp_sysfs.c
+++ b/drivers/ptp/ptp_sysfs.c
@@ -87,9 +87,6 @@ static ssize_t extts_fifo_show(struct device *dev,
 
 	memset(&event, 0, sizeof(event));
 
-	if (mutex_lock_interruptible(&ptp->tsevq_mux))
-		return -ERESTARTSYS;
-
 	spin_lock_irqsave(&queue->lock, flags);
 	qcnt = queue_cnt(queue);
 	if (qcnt) {
@@ -104,7 +101,6 @@ static ssize_t extts_fifo_show(struct device *dev,
 	cnt = snprintf(page, PAGE_SIZE, "%u %lld %u\n",
 		       event.index, event.t.sec, event.t.nsec);
 out:
-	mutex_unlock(&ptp->tsevq_mux);
 	return cnt;
 }
 static DEVICE_ATTR(fifo, 0444, extts_fifo_show, NULL);
-- 
2.34.1

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