tty: split the buffering from tty_io (e0495736) · Commits · EulixOS / Software / Kernel

drivers/char/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -7,7 +7,7 @@
		#
		FONTMAPFILE = cp437.uni

		obj-y += mem.o random.o tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o
		obj-y += mem.o random.o tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o tty_buffer.o

		obj-$(CONFIG_LEGACY_PTYS) += pty.o
		obj-$(CONFIG_UNIX98_PTYS) += pty.o

drivers/char/tty_buffer.c

0 → 100644

+511 −0

Original line number	Diff line number	Diff line
		/*
		* Tty buffer allocation management
		*/

		#include <linux/types.h>
		#include <linux/errno.h>
		#include <linux/tty.h>
		#include <linux/tty_driver.h>
		#include <linux/tty_flip.h>
		#include <linux/timer.h>
		#include <linux/string.h>
		#include <linux/slab.h>
		#include <linux/sched.h>
		#include <linux/init.h>
		#include <linux/wait.h>
		#include <linux/bitops.h>
		#include <linux/delay.h>
		#include <linux/module.h>

		/**
		* tty_buffer_free_all - free buffers used by a tty
		* @tty: tty to free from
		*
		* Remove all the buffers pending on a tty whether queued with data
		* or in the free ring. Must be called when the tty is no longer in use
		*
		* Locking: none
		*/

		void tty_buffer_free_all(struct tty_struct *tty)
		{
		struct tty_buffer *thead;
		while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		kfree(thead);
		}
		while ((thead = tty->buf.free) != NULL) {
		tty->buf.free = thead->next;
		kfree(thead);
		}
		tty->buf.tail = NULL;
		tty->buf.memory_used = 0;
		}

		/**
		* tty_buffer_alloc - allocate a tty buffer
		* @tty: tty device
		* @size: desired size (characters)
		*
		* Allocate a new tty buffer to hold the desired number of characters.
		* Return NULL if out of memory or the allocation would exceed the
		* per device queue
		*
		* Locking: Caller must hold tty->buf.lock
		*/

		static struct tty_buffer tty_buffer_alloc(struct tty_struct tty, size_t size)
		{
		struct tty_buffer *p;

		if (tty->buf.memory_used + size > 65536)
		return NULL;
		p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
		if (p == NULL)
		return NULL;
		p->used = 0;
		p->size = size;
		p->next = NULL;
		p->commit = 0;
		p->read = 0;
		p->char_buf_ptr = (char *)(p->data);
		p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
		tty->buf.memory_used += size;
		return p;
		}

		/**
		* tty_buffer_free - free a tty buffer
		* @tty: tty owning the buffer
		* @b: the buffer to free
		*
		* Free a tty buffer, or add it to the free list according to our
		* internal strategy
		*
		* Locking: Caller must hold tty->buf.lock
		*/

		static void tty_buffer_free(struct tty_struct tty, struct tty_buffer b)
		{
		/* Dumb strategy for now - should keep some stats */
		tty->buf.memory_used -= b->size;
		WARN_ON(tty->buf.memory_used < 0);

		if (b->size >= 512)
		kfree(b);
		else {
		b->next = tty->buf.free;
		tty->buf.free = b;
		}
		}

		/**
		* __tty_buffer_flush - flush full tty buffers
		* @tty: tty to flush
		*
		* flush all the buffers containing receive data. Caller must
		* hold the buffer lock and must have ensured no parallel flush to
		* ldisc is running.
		*
		* Locking: Caller must hold tty->buf.lock
		*/

		static void __tty_buffer_flush(struct tty_struct *tty)
		{
		struct tty_buffer *thead;

		while ((thead = tty->buf.head) != NULL) {
		tty->buf.head = thead->next;
		tty_buffer_free(tty, thead);
		}
		tty->buf.tail = NULL;
		}

		/**
		* tty_buffer_flush - flush full tty buffers
		* @tty: tty to flush
		*
		* flush all the buffers containing receive data. If the buffer is
		* being processed by flush_to_ldisc then we defer the processing
		* to that function
		*
		* Locking: none
		*/

		void tty_buffer_flush(struct tty_struct *tty)
		{
		unsigned long flags;
		spin_lock_irqsave(&tty->buf.lock, flags);

		/* If the data is being pushed to the tty layer then we can't
		process it here. Instead set a flag and the flush_to_ldisc
		path will process the flush request before it exits */
		if (test_bit(TTY_FLUSHING, &tty->flags)) {
		set_bit(TTY_FLUSHPENDING, &tty->flags);
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		wait_event(tty->read_wait,
		test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
		return;
		} else
		__tty_buffer_flush(tty);
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		}

		/**
		* tty_buffer_find - find a free tty buffer
		* @tty: tty owning the buffer
		* @size: characters wanted
		*
		* Locate an existing suitable tty buffer or if we are lacking one then
		* allocate a new one. We round our buffers off in 256 character chunks
		* to get better allocation behaviour.
		*
		* Locking: Caller must hold tty->buf.lock
		*/

		static struct tty_buffer tty_buffer_find(struct tty_struct tty, size_t size)
		{
		struct tty_buffer **tbh = &tty->buf.free;
		while ((*tbh) != NULL) {
		struct tty_buffer t = tbh;
		if (t->size >= size) {
		*tbh = t->next;
		t->next = NULL;
		t->used = 0;
		t->commit = 0;
		t->read = 0;
		tty->buf.memory_used += t->size;
		return t;
		}
		tbh = &((*tbh)->next);
		}
		/* Round the buffer size out */
		size = (size + 0xFF) & ~0xFF;
		return tty_buffer_alloc(tty, size);
		/* Should possibly check if this fails for the largest buffer we
		have queued and recycle that ? */
		}

		/**
		* tty_buffer_request_room - grow tty buffer if needed
		* @tty: tty structure
		* @size: size desired
		*
		* Make at least size bytes of linear space available for the tty
		* buffer. If we fail return the size we managed to find.
		*
		* Locking: Takes tty->buf.lock
		*/
		int tty_buffer_request_room(struct tty_struct *tty, size_t size)
		{
		struct tty_buffer b, n;
		int left;
		unsigned long flags;

		spin_lock_irqsave(&tty->buf.lock, flags);

		/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
		remove this conditional if its worth it. This would be invisible
		to the callers */
		if ((b = tty->buf.tail) != NULL)
		left = b->size - b->used;
		else
		left = 0;

		if (left < size) {
		/* This is the slow path - looking for new buffers to use */
		if ((n = tty_buffer_find(tty, size)) != NULL) {
		if (b != NULL) {
		b->next = n;
		b->commit = b->used;
		} else
		tty->buf.head = n;
		tty->buf.tail = n;
		} else
		size = left;
		}

		spin_unlock_irqrestore(&tty->buf.lock, flags);
		return size;
		}
		EXPORT_SYMBOL_GPL(tty_buffer_request_room);

		/**
		* tty_insert_flip_string - Add characters to the tty buffer
		* @tty: tty structure
		* @chars: characters
		* @size: size
		*
		* Queue a series of bytes to the tty buffering. All the characters
		* passed are marked as without error. Returns the number added.
		*
		* Locking: Called functions may take tty->buf.lock
		*/

		int tty_insert_flip_string(struct tty_struct tty, const unsigned char chars,
		size_t size)
		{
		int copied = 0;
		do {
		int space = tty_buffer_request_room(tty, size - copied);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
		break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
		copied += space;
		chars += space;
		/* There is a small chance that we need to split the data over
		several buffers. If this is the case we must loop */
		} while (unlikely(size > copied));
		return copied;
		}
		EXPORT_SYMBOL(tty_insert_flip_string);

		/**
		* tty_insert_flip_string_flags - Add characters to the tty buffer
		* @tty: tty structure
		* @chars: characters
		* @flags: flag bytes
		* @size: size
		*
		* Queue a series of bytes to the tty buffering. For each character
		* the flags array indicates the status of the character. Returns the
		* number added.
		*
		* Locking: Called functions may take tty->buf.lock
		*/

		int tty_insert_flip_string_flags(struct tty_struct *tty,
		const unsigned char chars, const char flags, size_t size)
		{
		int copied = 0;
		do {
		int space = tty_buffer_request_room(tty, size - copied);
		struct tty_buffer *tb = tty->buf.tail;
		/* If there is no space then tb may be NULL */
		if (unlikely(space == 0))
		break;
		memcpy(tb->char_buf_ptr + tb->used, chars, space);
		memcpy(tb->flag_buf_ptr + tb->used, flags, space);
		tb->used += space;
		copied += space;
		chars += space;
		flags += space;
		/* There is a small chance that we need to split the data over
		several buffers. If this is the case we must loop */
		} while (unlikely(size > copied));
		return copied;
		}
		EXPORT_SYMBOL(tty_insert_flip_string_flags);

		/**
		* tty_schedule_flip - push characters to ldisc
		* @tty: tty to push from
		*
		* Takes any pending buffers and transfers their ownership to the
		* ldisc side of the queue. It then schedules those characters for
		* processing by the line discipline.
		*
		* Locking: Takes tty->buf.lock
		*/

		void tty_schedule_flip(struct tty_struct *tty)
		{
		unsigned long flags;
		spin_lock_irqsave(&tty->buf.lock, flags);
		if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		schedule_delayed_work(&tty->buf.work, 1);
		}
		EXPORT_SYMBOL(tty_schedule_flip);

		/**
		* tty_prepare_flip_string - make room for characters
		* @tty: tty
		* @chars: return pointer for character write area
		* @size: desired size
		*
		* Prepare a block of space in the buffer for data. Returns the length
		* available and buffer pointer to the space which is now allocated and
		* accounted for as ready for normal characters. This is used for drivers
		* that need their own block copy routines into the buffer. There is no
		* guarantee the buffer is a DMA target!
		*
		* Locking: May call functions taking tty->buf.lock
		*/

		int tty_prepare_flip_string(struct tty_struct tty, unsigned char *chars,
		size_t size)
		{
		int space = tty_buffer_request_room(tty, size);
		if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
		tb->used += space;
		}
		return space;
		}
		EXPORT_SYMBOL_GPL(tty_prepare_flip_string);

		/**
		* tty_prepare_flip_string_flags - make room for characters
		* @tty: tty
		* @chars: return pointer for character write area
		* @flags: return pointer for status flag write area
		* @size: desired size
		*
		* Prepare a block of space in the buffer for data. Returns the length
		* available and buffer pointer to the space which is now allocated and
		* accounted for as ready for characters. This is used for drivers
		* that need their own block copy routines into the buffer. There is no
		* guarantee the buffer is a DMA target!
		*
		* Locking: May call functions taking tty->buf.lock
		*/

		int tty_prepare_flip_string_flags(struct tty_struct *tty,
		unsigned char chars, char flags, size_t size)
		{
		int space = tty_buffer_request_room(tty, size);
		if (likely(space)) {
		struct tty_buffer *tb = tty->buf.tail;
		*chars = tb->char_buf_ptr + tb->used;
		*flags = tb->flag_buf_ptr + tb->used;
		tb->used += space;
		}
		return space;
		}
		EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);



		/**
		* flush_to_ldisc
		* @work: tty structure passed from work queue.
		*
		* This routine is called out of the software interrupt to flush data
		* from the buffer chain to the line discipline.
		*
		* Locking: holds tty->buf.lock to guard buffer list. Drops the lock
		* while invoking the line discipline receive_buf method. The
		* receive_buf method is single threaded for each tty instance.
		*/

		static void flush_to_ldisc(struct work_struct *work)
		{
		struct tty_struct *tty =
		container_of(work, struct tty_struct, buf.work.work);
		unsigned long flags;
		struct tty_ldisc *disc;
		struct tty_buffer tbuf, head;
		char *char_buf;
		unsigned char *flag_buf;

		disc = tty_ldisc_ref(tty);
		if (disc == NULL) /* !TTY_LDISC */
		return;

		spin_lock_irqsave(&tty->buf.lock, flags);
		/* So we know a flush is running */
		set_bit(TTY_FLUSHING, &tty->flags);
		head = tty->buf.head;
		if (head != NULL) {
		tty->buf.head = NULL;
		for (;;) {
		int count = head->commit - head->read;
		if (!count) {
		if (head->next == NULL)
		break;
		tbuf = head;
		head = head->next;
		tty_buffer_free(tty, tbuf);
		continue;
		}
		/* Ldisc or user is trying to flush the buffers
		we are feeding to the ldisc, stop feeding the
		line discipline as we want to empty the queue */
		if (test_bit(TTY_FLUSHPENDING, &tty->flags))
		break;
		if (!tty->receive_room) {
		schedule_delayed_work(&tty->buf.work, 1);
		break;
		}
		if (count > tty->receive_room)
		count = tty->receive_room;
		char_buf = head->char_buf_ptr + head->read;
		flag_buf = head->flag_buf_ptr + head->read;
		head->read += count;
		spin_unlock_irqrestore(&tty->buf.lock, flags);
		disc->ops->receive_buf(tty, char_buf,
		flag_buf, count);
		spin_lock_irqsave(&tty->buf.lock, flags);
		}
		/* Restore the queue head */
		tty->buf.head = head;
		}
		/* We may have a deferred request to flush the input buffer,
		if so pull the chain under the lock and empty the queue */
		if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
		__tty_buffer_flush(tty);
		clear_bit(TTY_FLUSHPENDING, &tty->flags);
		wake_up(&tty->read_wait);
		}
		clear_bit(TTY_FLUSHING, &tty->flags);
		spin_unlock_irqrestore(&tty->buf.lock, flags);

		tty_ldisc_deref(disc);
		}

		/**
		* tty_flip_buffer_push - terminal
		* @tty: tty to push
		*
		* Queue a push of the terminal flip buffers to the line discipline. This
		* function must not be called from IRQ context if tty->low_latency is set.
		*
		* In the event of the queue being busy for flipping the work will be
		* held off and retried later.
		*
		* Locking: tty buffer lock. Driver locks in low latency mode.
		*/

		void tty_flip_buffer_push(struct tty_struct *tty)
		{
		unsigned long flags;
		spin_lock_irqsave(&tty->buf.lock, flags);
		if (tty->buf.tail != NULL)
		tty->buf.tail->commit = tty->buf.tail->used;
		spin_unlock_irqrestore(&tty->buf.lock, flags);

		if (tty->low_latency)
		flush_to_ldisc(&tty->buf.work.work);
		else
		schedule_delayed_work(&tty->buf.work, 1);
		}
		EXPORT_SYMBOL(tty_flip_buffer_push);

		/**
		* tty_buffer_init - prepare a tty buffer structure
		* @tty: tty to initialise
		*
		* Set up the initial state of the buffer management for a tty device.
		* Must be called before the other tty buffer functions are used.
		*
		* Locking: none
		*/

		void tty_buffer_init(struct tty_struct *tty)
		{
		spin_lock_init(&tty->buf.lock);
		tty->buf.head = NULL;
		tty->buf.tail = NULL;
		tty->buf.free = NULL;
		tty->buf.memory_used = 0;
		INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
		}

drivers/char/tty_io.c

+0 −502

File changed.

Preview size limit exceeded, changes collapsed.

include/linux/tty.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -347,6 +347,9 @@ extern void __do_SAK(struct tty_struct *tty);
		extern void disassociate_ctty(int priv);
		extern void no_tty(void);
		extern void tty_flip_buffer_push(struct tty_struct *tty);
		extern void tty_buffer_free_all(struct tty_struct *tty);
		extern void tty_buffer_flush(struct tty_struct *tty);
		extern void tty_buffer_init(struct tty_struct *tty);
		extern speed_t tty_get_baud_rate(struct tty_struct *tty);
		extern speed_t tty_termios_baud_rate(struct ktermios *termios);
		extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);