[PATCH] remove active field from tty buffer structure
Paul Fulghum [Wed, 28 Jun 2006 11:26:49 +0000 (04:26 -0700)]
Remove 'active' field from tty buffer structure.  This was added in 2.6.16
as part of a patch to make the new tty buffering SMP safe.  This field is
unnecessary with the more intelligently written flush_to_ldisc that adds
receive_room handling.

Removing this field reverts to simpler logic where the tail buffer is
always the 'active' buffer, which should not be freed by flush_to_ldisc.
(active == buffer being filled with new data)

The result is simpler, smaller, and faster tty buffer code.

Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/tty_io.c
include/linux/kbd_kern.h
include/linux/tty.h
include/linux/tty_flip.h

index 1f03ebf..8d19f72 100644 (file)
@@ -267,7 +267,6 @@ static struct tty_buffer *tty_buffer_alloc(size_t size)
        p->used = 0;
        p->size = size;
        p->next = NULL;
-       p->active = 0;
        p->commit = 0;
        p->read = 0;
        p->char_buf_ptr = (char *)(p->data);
@@ -327,10 +326,9 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
        /* 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) {
+       if ((b = tty->buf.tail) != NULL)
                left = b->size - b->used;
-               b->active = 1;
-       } else
+       else
                left = 0;
 
        if (left < size) {
@@ -338,12 +336,10 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size)
                if ((n = tty_buffer_find(tty, size)) != NULL) {
                        if (b != NULL) {
                                b->next = n;
-                               b->active = 0;
                                b->commit = b->used;
                        } else
                                tty->buf.head = n;
                        tty->buf.tail = n;
-                       n->active = 1;
                } else
                        size = left;
        }
@@ -404,10 +400,8 @@ 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->active = 0;
+       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);
 }
@@ -2902,10 +2896,8 @@ 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->active = 0;
+       if (tty->buf.tail != NULL)
                tty->buf.tail->commit = tty->buf.tail->used;
-       }
        spin_unlock_irqrestore(&tty->buf.lock, flags);
 
        if (tty->low_latency)
index 4eb851e..efe0ee4 100644 (file)
@@ -155,10 +155,8 @@ static inline void con_schedule_flip(struct tty_struct *t)
 {
        unsigned long flags;
        spin_lock_irqsave(&t->buf.lock, flags);
-       if (t->buf.tail != NULL) {
-               t->buf.tail->active = 0;
+       if (t->buf.tail != NULL)
                t->buf.tail->commit = t->buf.tail->used;
-       }
        spin_unlock_irqrestore(&t->buf.lock, flags);
        schedule_work(&t->buf.work);
 }
index 341cc45..b3b807e 100644 (file)
@@ -57,7 +57,6 @@ struct tty_buffer {
        unsigned char *flag_buf_ptr;
        int used;
        int size;
-       int active;
        int commit;
        int read;
        /* Data points here */
index 3154830..eb677cf 100644 (file)
@@ -12,7 +12,7 @@ static inline int tty_insert_flip_char(struct tty_struct *tty,
                                        unsigned char ch, char flag)
 {
        struct tty_buffer *tb = tty->buf.tail;
-       if (tb && tb->active && tb->used < tb->size) {
+       if (tb && tb->used < tb->size) {
                tb->flag_buf_ptr[tb->used] = flag;
                tb->char_buf_ptr[tb->used++] = ch;
                return 1;