Commit adc839ae authored by Takashi Sakamoto's avatar Takashi Sakamoto
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firewire: core: use mutex instead of spinlock for client isochronous context 

There is a restriction that the userspace client associated to a file
descriptor can hold one isochronous context. The client-level spinning
lock is used to guarantee it, however the lock is also used for
multi-purposes. Additionally, there is no need to use this type of lock,
and the mutex is available, instead.

Link: https://lore.kernel.org/r/20260110013911.19160-3-o-takashi@sakamocchi.jp


Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
parent c91adadd

drivers/firewire/core-cdev.c

+23 −17
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ struct client { 
	u64 bus_reset_closure;



	struct fw_iso_context *iso_context;

	struct mutex iso_context_mutex;

	u64 iso_closure;

	struct fw_iso_buffer buffer;

	unsigned long vm_start;
@@ -306,6 +307,7 @@ static int fw_device_op_open(struct inode *inode, struct file *file) 
	INIT_LIST_HEAD(&client->phy_receiver_link);

	INIT_LIST_HEAD(&client->link);

	kref_init(&client->kref);

	mutex_init(&client->iso_context_mutex);



	file->private_data = client;
@@ -1088,16 +1090,16 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg) 
		context->drop_overflow_headers = true;



	// We only support one context at this time.

	guard(spinlock_irq)(&client->lock);



	scoped_guard(mutex, &client->iso_context_mutex) {

		if (client->iso_context != NULL) {

			fw_iso_context_destroy(context);



			return -EBUSY;

		}

		// The DMA mapping operation is available if the buffer is already allocated by

		// mmap(2) system call. If not, it is delegated to the system call.

		if (!client->buffer_is_mapped) {

		ret = fw_iso_buffer_map_dma(&client->buffer,

					    client->device->card,

			ret = fw_iso_buffer_map_dma(&client->buffer, client->device->card,

						    iso_dma_direction(context));

			if (ret < 0) {

				fw_iso_context_destroy(context);
@@ -1108,6 +1110,7 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg) 
		}

		client->iso_closure = a->closure;

		client->iso_context = context;

	}



	a->handle = 0;
@@ -1826,7 +1829,9 @@ static int fw_device_op_mmap(struct file *file, struct vm_area_struct *vma) 
	if (ret < 0)

		return ret;



	scoped_guard(spinlock_irq, &client->lock) {

	scoped_guard(mutex, &client->iso_context_mutex) {

		// The direction of DMA can be determined if the isochronous context is already

		// allocated. If not, the DMA mapping operation is postponed after the allocation.

		if (client->iso_context) {

			ret = fw_iso_buffer_map_dma(&client->buffer, client->device->card,

						    iso_dma_direction(client->iso_context));
@@ -1879,6 +1884,7 @@ static int fw_device_op_release(struct inode *inode, struct file *file) 


	if (client->iso_context)

		fw_iso_context_destroy(client->iso_context);

	mutex_destroy(&client->iso_context_mutex);



	if (client->buffer.pages)

		fw_iso_buffer_destroy(&client->buffer, client->device->card);