diff options
Diffstat (limited to 'drivers/tty/tty_buffer.c')
| -rw-r--r-- | drivers/tty/tty_buffer.c | 150 |
1 files changed, 82 insertions, 68 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index c043136fbe5..143deb62467 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -11,7 +11,6 @@ #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> @@ -26,7 +25,7 @@ * Byte threshold to limit memory consumption for flip buffers. * The actual memory limit is > 2x this amount. */ -#define TTYB_MEM_LIMIT 65536 +#define TTYB_DEFAULT_MEM_LIMIT 65536 /* * We default to dicing tty buffer allocations to this many characters @@ -61,6 +60,7 @@ void tty_buffer_lock_exclusive(struct tty_port *port) atomic_inc(&buf->priority); mutex_lock(&buf->lock); } +EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive); void tty_buffer_unlock_exclusive(struct tty_port *port) { @@ -74,6 +74,7 @@ void tty_buffer_unlock_exclusive(struct tty_port *port) if (restart) queue_work(system_unbound_wq, &buf->work); } +EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive); /** * tty_buffer_space_avail - return unused buffer space @@ -89,9 +90,10 @@ void tty_buffer_unlock_exclusive(struct tty_port *port) int tty_buffer_space_avail(struct tty_port *port) { - int space = TTYB_MEM_LIMIT - atomic_read(&port->buf.memory_used); + int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); return max(space, 0); } +EXPORT_SYMBOL_GPL(tty_buffer_space_avail); static void tty_buffer_reset(struct tty_buffer *p, size_t size) { @@ -100,6 +102,7 @@ static void tty_buffer_reset(struct tty_buffer *p, size_t size) p->next = NULL; p->commit = 0; p->read = 0; + p->flags = 0; } /** @@ -129,7 +132,7 @@ void tty_buffer_free_all(struct tty_port *port) buf->head = &buf->sentinel; buf->tail = &buf->sentinel; - atomic_set(&buf->memory_used, 0); + atomic_set(&buf->mem_used, 0); } /** @@ -162,7 +165,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) /* Should possibly check if this fails for the largest buffer we have queued and recycle that ? */ - if (atomic_read(&port->buf.memory_used) > TTYB_MEM_LIMIT) + if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) return NULL; p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); if (p == NULL) @@ -170,7 +173,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) found: tty_buffer_reset(p, size); - atomic_add(size, &port->buf.memory_used); + atomic_add(size, &port->buf.mem_used); return p; } @@ -188,7 +191,7 @@ static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) struct tty_bufhead *buf = &port->buf; /* Dumb strategy for now - should keep some stats */ - WARN_ON(atomic_sub_return(b->size, &buf->memory_used) < 0); + WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); if (b->size > MIN_TTYB_SIZE) kfree(b); @@ -200,9 +203,7 @@ static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) * 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 + * flush all the buffers containing receive data. * * Locking: takes buffer lock to ensure single-threaded flip buffer * 'consumer' @@ -230,31 +231,53 @@ void tty_buffer_flush(struct tty_struct *tty) * tty_buffer_request_room - grow tty buffer if needed * @tty: tty structure * @size: size desired + * @flags: buffer flags if new buffer allocated (default = 0) * * Make at least size bytes of linear space available for the tty * buffer. If we fail return the size we managed to find. + * + * Will change over to a new buffer if the current buffer is encoded as + * TTY_NORMAL (so has no flags buffer) and the new buffer requires + * a flags buffer. */ -int tty_buffer_request_room(struct tty_port *port, size_t size) +static int __tty_buffer_request_room(struct tty_port *port, size_t size, + int flags) { struct tty_bufhead *buf = &port->buf; struct tty_buffer *b, *n; - int left; + int left, change; b = buf->tail; - left = b->size - b->used; + if (b->flags & TTYB_NORMAL) + left = 2 * b->size - b->used; + else + left = b->size - b->used; - if (left < size) { + change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); + if (change || left < size) { /* This is the slow path - looking for new buffers to use */ if ((n = tty_buffer_alloc(port, size)) != NULL) { + n->flags = flags; buf->tail = n; b->commit = b->used; - smp_mb(); + /* paired w/ barrier in flush_to_ldisc(); ensures the + * latest commit value can be read before the head is + * advanced to the next buffer + */ + smp_wmb(); b->next = n; - } else + } else if (change) + size = 0; + else size = left; } return size; } + +int tty_buffer_request_room(struct tty_port *port, size_t size) +{ + return __tty_buffer_request_room(port, size, 0); +} EXPORT_SYMBOL_GPL(tty_buffer_request_room); /** @@ -274,12 +297,14 @@ int tty_insert_flip_string_fixed_flag(struct tty_port *port, int copied = 0; do { int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); - int space = tty_buffer_request_room(port, goal); + int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; + int space = __tty_buffer_request_room(port, goal, flags); struct tty_buffer *tb = port->buf.tail; if (unlikely(space == 0)) break; memcpy(char_buf_ptr(tb, tb->used), chars, space); - memset(flag_buf_ptr(tb, tb->used), flag, space); + if (~tb->flags & TTYB_NORMAL) + memset(flag_buf_ptr(tb, tb->used), flag, space); tb->used += space; copied += space; chars += space; @@ -332,14 +357,11 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags); * 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. - * Note that this function can only be used when the low_latency flag - * is unset. Otherwise the workqueue won't be flushed. */ void tty_schedule_flip(struct tty_port *port) { struct tty_bufhead *buf = &port->buf; - WARN_ON(port->low_latency); buf->tail->commit = buf->tail->used; schedule_work(&buf->work); @@ -362,52 +384,28 @@ EXPORT_SYMBOL(tty_schedule_flip); int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, size_t size) { - int space = tty_buffer_request_room(port, size); + int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); if (likely(space)) { struct tty_buffer *tb = port->buf.tail; *chars = char_buf_ptr(tb, tb->used); - memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); + if (~tb->flags & TTYB_NORMAL) + memset(flag_buf_ptr(tb, 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 - * @port: tty port - * @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! - */ - -int tty_prepare_flip_string_flags(struct tty_port *port, - unsigned char **chars, char **flags, size_t size) -{ - int space = tty_buffer_request_room(port, size); - if (likely(space)) { - struct tty_buffer *tb = port->buf.tail; - *chars = char_buf_ptr(tb, tb->used); - *flags = flag_buf_ptr(tb, tb->used); - tb->used += space; - } - return space; -} -EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); - static int receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count) { struct tty_ldisc *disc = tty->ldisc; unsigned char *p = char_buf_ptr(head, head->read); - char *f = flag_buf_ptr(head, head->read); + char *f = NULL; + + if (~head->flags & TTYB_NORMAL) + f = flag_buf_ptr(head, head->read); if (disc->ops->receive_buf2) count = disc->ops->receive_buf2(tty, p, f, count); @@ -452,17 +450,24 @@ static void flush_to_ldisc(struct work_struct *work) while (1) { struct tty_buffer *head = buf->head; + struct tty_buffer *next; int count; /* Ldisc or user is trying to gain exclusive access */ if (atomic_read(&buf->priority)) break; + next = head->next; + /* paired w/ barrier in __tty_buffer_request_room(); + * ensures commit value read is not stale if the head + * is advancing to the next buffer + */ + smp_rmb(); count = head->commit - head->read; if (!count) { - if (head->next == NULL) + if (next == NULL) break; - buf->head = head->next; + buf->head = next; tty_buffer_free(port, head); continue; } @@ -487,17 +492,15 @@ static void flush_to_ldisc(struct work_struct *work) */ void tty_flush_to_ldisc(struct tty_struct *tty) { - if (!tty->port->low_latency) - flush_work(&tty->port->buf.work); + flush_work(&tty->port->buf.work); } /** * tty_flip_buffer_push - terminal * @port: tty port to push * - * Queue a push of the terminal flip buffers to the line discipline. This - * function must not be called from IRQ context if port->low_latency is - * set. + * Queue a push of the terminal flip buffers to the line discipline. + * Can be called from IRQ/atomic context. * * In the event of the queue being busy for flipping the work will be * held off and retried later. @@ -505,14 +508,7 @@ void tty_flush_to_ldisc(struct tty_struct *tty) void tty_flip_buffer_push(struct tty_port *port) { - struct tty_bufhead *buf = &port->buf; - - buf->tail->commit = buf->tail->used; - - if (port->low_latency) - flush_to_ldisc(&buf->work); - else - schedule_work(&buf->work); + tty_schedule_flip(port); } EXPORT_SYMBOL(tty_flip_buffer_push); @@ -533,7 +529,25 @@ void tty_buffer_init(struct tty_port *port) buf->head = &buf->sentinel; buf->tail = &buf->sentinel; init_llist_head(&buf->free); - atomic_set(&buf->memory_used, 0); + atomic_set(&buf->mem_used, 0); atomic_set(&buf->priority, 0); INIT_WORK(&buf->work, flush_to_ldisc); + buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; +} + +/** + * tty_buffer_set_limit - change the tty buffer memory limit + * @port: tty port to change + * + * Change the tty buffer memory limit. + * Must be called before the other tty buffer functions are used. + */ + +int tty_buffer_set_limit(struct tty_port *port, int limit) +{ + if (limit < MIN_TTYB_SIZE) + return -EINVAL; + port->buf.mem_limit = limit; + return 0; } +EXPORT_SYMBOL_GPL(tty_buffer_set_limit); |