diff options
| -rw-r--r-- | drivers/char/tty_io.c | 89 | ||||
| -rw-r--r-- | include/linux/tty.h | 1 |
2 files changed, 80 insertions, 10 deletions
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index 2cef982585f0..bb0d9199e994 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -275,6 +275,17 @@ static int check_tty_count(struct tty_struct *tty, const char *routine) * Locking: none */ + +/** + * 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 + */ + static void tty_buffer_free_all(struct tty_struct *tty) { struct tty_buffer *thead; @@ -287,19 +298,47 @@ static void tty_buffer_free_all(struct tty_struct *tty) kfree(thead); } tty->buf.tail = NULL; + tty->buf.memory_used = 0; } +/** + * 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 + */ + static 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; } -static struct tty_buffer *tty_buffer_alloc(size_t size) +/** + * 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 = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); + 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; @@ -309,17 +348,27 @@ static struct tty_buffer *tty_buffer_alloc(size_t size) p->read = 0; p->char_buf_ptr = (char *)(p->data); p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size; -/* printk("Flip create %p\n", p); */ + tty->buf.memory_used += size; return p; } -/* Must be called with the tty_read lock held. This needs to acquire strategy - code to decide if we should kfree or relink a given expired buffer */ +/** + * 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 */ -/* printk("Flip dispose %p\n", b); */ + tty->buf.memory_used -= b->size; + WARN_ON(tty->buf.memory_used < 0); + if(b->size >= 512) kfree(b); else { @@ -328,6 +377,18 @@ static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b) } } +/** + * 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; @@ -339,20 +400,28 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) t->used = 0; t->commit = 0; t->read = 0; - /* DEBUG ONLY */ -/* memset(t->data, '*', size); */ -/* printk("Flip recycle %p\n", t); */ + tty->buf.memory_used += t->size; return t; } tbh = &((*tbh)->next); } /* Round the buffer size out */ size = (size + 0xFF) & ~ 0xFF; - return tty_buffer_alloc(size); + 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; diff --git a/include/linux/tty.h b/include/linux/tty.h index e421d5e34818..04827ca65781 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -59,6 +59,7 @@ struct tty_bufhead { struct tty_buffer *head; /* Queue head */ struct tty_buffer *tail; /* Active buffer */ struct tty_buffer *free; /* Free queue head */ + int memory_used; /* Buffer space used excluding free queue */ }; /* * The pty uses char_buf and flag_buf as a contiguous buffer |