From 8977d929e49021d9a6e031310aab01fa72f849c2 Mon Sep 17 00:00:00 2001 From: Paul Fulghum Date: Fri, 10 Feb 2006 01:51:14 -0800 Subject: [PATCH] [PATCH] tty buffering stall fix Prevent stalled processing of received data when a driver allocates tty buffer space but does not immediately follow the allocation with more data and a call to schedule receive tty processing. (example: hvc_console) This bug was introduced by the first locking patch for the new tty buffering. Signed-off-by: Paul Fulghum Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/char/tty_io.c | 30 ++++++++++++++++++++++-------- include/linux/kbd_kern.h | 4 +++- include/linux/tty.h | 2 ++ include/linux/tty_flip.h | 4 +++- 4 files changed, 30 insertions(+), 10 deletions(-) diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index 076e07c1da38..a23816d3e9a1 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -268,6 +268,8 @@ static struct tty_buffer *tty_buffer_alloc(size_t size) p->size = size; p->next = NULL; p->active = 0; + p->commit = 0; + 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); */ @@ -298,6 +300,8 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) *tbh = t->next; t->next = NULL; t->used = 0; + t->commit = 0; + t->read = 0; /* DEBUG ONLY */ memset(t->data, '*', size); /* printk("Flip recycle %p\n", t); */ @@ -335,6 +339,7 @@ int tty_buffer_request_room(struct tty_struct *tty, size_t size) if (b != NULL) { b->next = n; b->active = 0; + b->commit = b->used; } else tty->buf.head = n; tty->buf.tail = n; @@ -2752,6 +2757,9 @@ static void flush_to_ldisc(void *private_) unsigned long flags; struct tty_ldisc *disc; struct tty_buffer *tbuf; + int count; + char *char_buf; + unsigned char *flag_buf; disc = tty_ldisc_ref(tty); if (disc == NULL) /* !TTY_LDISC */ @@ -2765,16 +2773,20 @@ static void flush_to_ldisc(void *private_) goto out; } spin_lock_irqsave(&tty->buf.lock, flags); - while((tbuf = tty->buf.head) != NULL && !tbuf->active) { + while((tbuf = tty->buf.head) != NULL) { + while ((count = tbuf->commit - tbuf->read) != 0) { + char_buf = tbuf->char_buf_ptr + tbuf->read; + flag_buf = tbuf->flag_buf_ptr + tbuf->read; + tbuf->read += count; + spin_unlock_irqrestore(&tty->buf.lock, flags); + disc->receive_buf(tty, char_buf, flag_buf, count); + spin_lock_irqsave(&tty->buf.lock, flags); + } + if (tbuf->active) + break; tty->buf.head = tbuf->next; if (tty->buf.head == NULL) tty->buf.tail = NULL; - spin_unlock_irqrestore(&tty->buf.lock, flags); - /* printk("Process buffer %p for %d\n", tbuf, tbuf->used); */ - disc->receive_buf(tty, tbuf->char_buf_ptr, - tbuf->flag_buf_ptr, - tbuf->used); - spin_lock_irqsave(&tty->buf.lock, flags); tty_buffer_free(tty, tbuf); } spin_unlock_irqrestore(&tty->buf.lock, flags); @@ -2871,8 +2883,10 @@ void tty_flip_buffer_push(struct tty_struct *tty) { unsigned long flags; spin_lock_irqsave(&tty->buf.lock, flags); - if (tty->buf.tail != NULL) + if (tty->buf.tail != NULL) { tty->buf.tail->active = 0; + tty->buf.tail->commit = tty->buf.tail->used; + } spin_unlock_irqrestore(&tty->buf.lock, flags); if (tty->low_latency) diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h index 3aed37314ab8..e87c32a5c86a 100644 --- a/include/linux/kbd_kern.h +++ b/include/linux/kbd_kern.h @@ -153,8 +153,10 @@ 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) + if (t->buf.tail != NULL) { t->buf.tail->active = 0; + t->buf.tail->commit = t->buf.tail->used; + } spin_unlock_irqrestore(&t->buf.lock, flags); schedule_work(&t->buf.work); } diff --git a/include/linux/tty.h b/include/linux/tty.h index a7bd3b4558d2..f45cd74e6f24 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -58,6 +58,8 @@ struct tty_buffer { int used; int size; int active; + int commit; + int read; /* Data points here */ unsigned long data[0]; }; diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h index 82961eb19888..222faf97d5f9 100644 --- a/include/linux/tty_flip.h +++ b/include/linux/tty_flip.h @@ -29,8 +29,10 @@ _INLINE_ void tty_schedule_flip(struct tty_struct *tty) { unsigned long flags; spin_lock_irqsave(&tty->buf.lock, flags); - if (tty->buf.tail != NULL) + if (tty->buf.tail != NULL) { tty->buf.tail->active = 0; + tty->buf.tail->commit = tty->buf.tail->used; + } spin_unlock_irqrestore(&tty->buf.lock, flags); schedule_delayed_work(&tty->buf.work, 1); } -- 2.20.1