From cee4ad1ed90a0959fc29f9d30a2526e5e9522cfa Mon Sep 17 00:00:00 2001 From: Ivo Sieben Date: Thu, 27 Sep 2012 14:02:05 +0200 Subject: tty: prevent unnecessary work queue lock checking on flip buffer copy When low_latency flag is set the TTY receive flip buffer is copied to the line discipline directly instead of using a work queue in the background. Therefor only in case a workqueue is actually used for copying data to the line discipline we'll have to flush the workqueue. This prevents unnecessary spin lock/unlock on the workqueue spin lock that can cause additional scheduling overhead on a PREEMPT_RT system. On a 200 MHz AT91SAM9261 processor setup this fixes about 100us of scheduling overhead on the TTY read call. Signed-off-by: Ivo Sieben Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/tty/tty_buffer.c') diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 91e326ffe7db..8b00f6a34a7d 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -342,6 +342,8 @@ 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. * * Locking: Takes tty->buf.lock */ @@ -514,7 +516,8 @@ static void flush_to_ldisc(struct work_struct *work) */ void tty_flush_to_ldisc(struct tty_struct *tty) { - flush_work(&tty->buf.work); + if (!tty->low_latency) + flush_work(&tty->buf.work); } /** -- cgit v1.2.2 From 2fc20661e3171d45e8e58a61eb5c6b7d8d614fde Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 18 Oct 2012 22:26:44 +0200 Subject: TTY: move TTY_FLUSH* flags to tty_port They are only TTY buffers specific. And the buffers will go to tty_port in the next patches. So to remove the need to have both tty_port and tty_struct at some places, let us move the flags to tty_port. Signed-off-by: Jiri Slaby Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'drivers/tty/tty_buffer.c') diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 8b00f6a34a7d..6f366f257fba 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -134,17 +134,18 @@ static void __tty_buffer_flush(struct tty_struct *tty) void tty_buffer_flush(struct tty_struct *tty) { + struct tty_port *port = tty->port; 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); + if (test_bit(TTYP_FLUSHING, &port->iflags)) { + set_bit(TTYP_FLUSHPENDING, &port->iflags); spin_unlock_irqrestore(&tty->buf.lock, flags); wait_event(tty->read_wait, - test_bit(TTY_FLUSHPENDING, &tty->flags) == 0); + test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0); return; } else __tty_buffer_flush(tty); @@ -450,6 +451,7 @@ static void flush_to_ldisc(struct work_struct *work) { struct tty_struct *tty = container_of(work, struct tty_struct, buf.work); + struct tty_port *port = tty->port; unsigned long flags; struct tty_ldisc *disc; @@ -459,7 +461,7 @@ static void flush_to_ldisc(struct work_struct *work) spin_lock_irqsave(&tty->buf.lock, flags); - if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) { + if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) { struct tty_buffer *head; while ((head = tty->buf.head) != NULL) { int count; @@ -477,7 +479,7 @@ static void flush_to_ldisc(struct work_struct *work) /* 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)) + if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) break; if (!tty->receive_room) break; @@ -491,14 +493,14 @@ static void flush_to_ldisc(struct work_struct *work) flag_buf, count); spin_lock_irqsave(&tty->buf.lock, flags); } - clear_bit(TTY_FLUSHING, &tty->flags); + clear_bit(TTYP_FLUSHING, &port->iflags); } /* 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)) { + if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) { __tty_buffer_flush(tty); - clear_bit(TTY_FLUSHPENDING, &tty->flags); + clear_bit(TTYP_FLUSHPENDING, &port->iflags); wake_up(&tty->read_wait); } spin_unlock_irqrestore(&tty->buf.lock, flags); -- cgit v1.2.2 From 5cff39c69b57df6d7bf4e87f2963571aa4ea6336 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 18 Oct 2012 22:26:45 +0200 Subject: TTY: tty_buffer, cache pointer to tty->buf During the move of tty buffers from tty_struct to tty_port, we will need to switch all users of buf to tty->port->buf. There are many functions where this is accessed directly in their code many times. Cache the tty->buf pointer in such functions now and change only single lines in each function in the next patch. Not that it is convenient for the next patch, but the code is now also more readable. Signed-off-by: Jiri Slaby Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 132 +++++++++++++++++++++++++++-------------------- 1 file changed, 76 insertions(+), 56 deletions(-) (limited to 'drivers/tty/tty_buffer.c') diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 6f366f257fba..ddd74d41cbb2 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -29,17 +29,19 @@ void tty_buffer_free_all(struct tty_struct *tty) { + struct tty_bufhead *buf = &tty->buf; struct tty_buffer *thead; - while ((thead = tty->buf.head) != NULL) { - tty->buf.head = thead->next; + + while ((thead = buf->head) != NULL) { + buf->head = thead->next; kfree(thead); } - while ((thead = tty->buf.free) != NULL) { - tty->buf.free = thead->next; + while ((thead = buf->free) != NULL) { + buf->free = thead->next; kfree(thead); } - tty->buf.tail = NULL; - tty->buf.memory_used = 0; + buf->tail = NULL; + buf->memory_used = 0; } /** @@ -87,15 +89,17 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size) static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b) { + struct tty_bufhead *buf = &tty->buf; + /* Dumb strategy for now - should keep some stats */ - tty->buf.memory_used -= b->size; - WARN_ON(tty->buf.memory_used < 0); + buf->memory_used -= b->size; + WARN_ON(buf->memory_used < 0); if (b->size >= 512) kfree(b); else { - b->next = tty->buf.free; - tty->buf.free = b; + b->next = buf->free; + buf->free = b; } } @@ -112,13 +116,14 @@ static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b) static void __tty_buffer_flush(struct tty_struct *tty) { + struct tty_bufhead *buf = &tty->buf; struct tty_buffer *thead; - while ((thead = tty->buf.head) != NULL) { - tty->buf.head = thead->next; + while ((thead = buf->head) != NULL) { + buf->head = thead->next; tty_buffer_free(tty, thead); } - tty->buf.tail = NULL; + buf->tail = NULL; } /** @@ -135,21 +140,23 @@ static void __tty_buffer_flush(struct tty_struct *tty) void tty_buffer_flush(struct tty_struct *tty) { struct tty_port *port = tty->port; + struct tty_bufhead *buf = &tty->buf; unsigned long flags; - spin_lock_irqsave(&tty->buf.lock, flags); + + spin_lock_irqsave(&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(TTYP_FLUSHING, &port->iflags)) { set_bit(TTYP_FLUSHPENDING, &port->iflags); - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); wait_event(tty->read_wait, test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0); return; } else __tty_buffer_flush(tty); - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); } /** @@ -197,12 +204,14 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) */ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) { + struct tty_bufhead *buf = &tty->buf; struct tty_buffer *b, *n; int left; /* 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) + b = buf->tail; + if (b != NULL) left = b->size - b->used; else left = 0; @@ -214,8 +223,8 @@ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) b->next = n; b->commit = b->used; } else - tty->buf.head = n; - tty->buf.tail = n; + buf->head = n; + buf->tail = n; } else size = left; } @@ -262,6 +271,7 @@ EXPORT_SYMBOL_GPL(tty_buffer_request_room); int tty_insert_flip_string_fixed_flag(struct tty_struct *tty, const unsigned char *chars, char flag, size_t size) { + struct tty_bufhead *buf = &tty->buf; int copied = 0; do { int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); @@ -269,18 +279,18 @@ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty, unsigned long flags; struct tty_buffer *tb; - spin_lock_irqsave(&tty->buf.lock, flags); + spin_lock_irqsave(&buf->lock, flags); space = __tty_buffer_request_room(tty, goal); - tb = tty->buf.tail; + tb = buf->tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) { - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); break; } memcpy(tb->char_buf_ptr + tb->used, chars, space); memset(tb->flag_buf_ptr + tb->used, flag, space); tb->used += space; - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); copied += space; chars += space; /* There is a small chance that we need to split the data over @@ -307,6 +317,7 @@ EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); int tty_insert_flip_string_flags(struct tty_struct *tty, const unsigned char *chars, const char *flags, size_t size) { + struct tty_bufhead *buf = &tty->buf; int copied = 0; do { int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); @@ -314,18 +325,18 @@ int tty_insert_flip_string_flags(struct tty_struct *tty, unsigned long __flags; struct tty_buffer *tb; - spin_lock_irqsave(&tty->buf.lock, __flags); + spin_lock_irqsave(&buf->lock, __flags); space = __tty_buffer_request_room(tty, goal); - tb = tty->buf.tail; + tb = buf->tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) { - spin_unlock_irqrestore(&tty->buf.lock, __flags); + spin_unlock_irqrestore(&buf->lock, __flags); break; } memcpy(tb->char_buf_ptr + tb->used, chars, space); memcpy(tb->flag_buf_ptr + tb->used, flags, space); tb->used += space; - spin_unlock_irqrestore(&tty->buf.lock, __flags); + spin_unlock_irqrestore(&buf->lock, __flags); copied += space; chars += space; flags += space; @@ -351,12 +362,14 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags); void tty_schedule_flip(struct tty_struct *tty) { + struct tty_bufhead *buf = &tty->buf; 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_work(&tty->buf.work); + + spin_lock_irqsave(&buf->lock, flags); + if (buf->tail != NULL) + buf->tail->commit = buf->tail->used; + spin_unlock_irqrestore(&buf->lock, flags); + schedule_work(&buf->work); } EXPORT_SYMBOL(tty_schedule_flip); @@ -378,20 +391,21 @@ EXPORT_SYMBOL(tty_schedule_flip); int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, size_t size) { + struct tty_bufhead *buf = &tty->buf; int space; unsigned long flags; struct tty_buffer *tb; - spin_lock_irqsave(&tty->buf.lock, flags); + spin_lock_irqsave(&buf->lock, flags); space = __tty_buffer_request_room(tty, size); - tb = tty->buf.tail; + tb = buf->tail; if (likely(space)) { *chars = tb->char_buf_ptr + tb->used; memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space); tb->used += space; } - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); return space; } EXPORT_SYMBOL_GPL(tty_prepare_flip_string); @@ -415,20 +429,21 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string); int tty_prepare_flip_string_flags(struct tty_struct *tty, unsigned char **chars, char **flags, size_t size) { + struct tty_bufhead *buf = &tty->buf; int space; unsigned long __flags; struct tty_buffer *tb; - spin_lock_irqsave(&tty->buf.lock, __flags); + spin_lock_irqsave(&buf->lock, __flags); space = __tty_buffer_request_room(tty, size); - tb = tty->buf.tail; + tb = buf->tail; if (likely(space)) { *chars = tb->char_buf_ptr + tb->used; *flags = tb->flag_buf_ptr + tb->used; tb->used += space; } - spin_unlock_irqrestore(&tty->buf.lock, __flags); + spin_unlock_irqrestore(&buf->lock, __flags); return space; } EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); @@ -452,6 +467,7 @@ static void flush_to_ldisc(struct work_struct *work) struct tty_struct *tty = container_of(work, struct tty_struct, buf.work); struct tty_port *port = tty->port; + struct tty_bufhead *buf = &tty->buf; unsigned long flags; struct tty_ldisc *disc; @@ -459,11 +475,11 @@ static void flush_to_ldisc(struct work_struct *work) if (disc == NULL) /* !TTY_LDISC */ return; - spin_lock_irqsave(&tty->buf.lock, flags); + spin_lock_irqsave(&buf->lock, flags); if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) { struct tty_buffer *head; - while ((head = tty->buf.head) != NULL) { + while ((head = buf->head) != NULL) { int count; char *char_buf; unsigned char *flag_buf; @@ -472,7 +488,7 @@ static void flush_to_ldisc(struct work_struct *work) if (!count) { if (head->next == NULL) break; - tty->buf.head = head->next; + buf->head = head->next; tty_buffer_free(tty, head); continue; } @@ -488,10 +504,10 @@ static void flush_to_ldisc(struct work_struct *work) 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); + spin_unlock_irqrestore(&buf->lock, flags); disc->ops->receive_buf(tty, char_buf, flag_buf, count); - spin_lock_irqsave(&tty->buf.lock, flags); + spin_lock_irqsave(&buf->lock, flags); } clear_bit(TTYP_FLUSHING, &port->iflags); } @@ -503,7 +519,7 @@ static void flush_to_ldisc(struct work_struct *work) clear_bit(TTYP_FLUSHPENDING, &port->iflags); wake_up(&tty->read_wait); } - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_unlock_irqrestore(&buf->lock, flags); tty_ldisc_deref(disc); } @@ -537,16 +553,18 @@ void tty_flush_to_ldisc(struct tty_struct *tty) void tty_flip_buffer_push(struct tty_struct *tty) { + struct tty_bufhead *buf = &tty->buf; 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); + + spin_lock_irqsave(&buf->lock, flags); + if (buf->tail != NULL) + buf->tail->commit = buf->tail->used; + spin_unlock_irqrestore(&buf->lock, flags); if (tty->low_latency) - flush_to_ldisc(&tty->buf.work); + flush_to_ldisc(&buf->work); else - schedule_work(&tty->buf.work); + schedule_work(&buf->work); } EXPORT_SYMBOL(tty_flip_buffer_push); @@ -562,11 +580,13 @@ EXPORT_SYMBOL(tty_flip_buffer_push); 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_WORK(&tty->buf.work, flush_to_ldisc); + struct tty_bufhead *buf = &tty->buf; + + spin_lock_init(&buf->lock); + buf->head = NULL; + buf->tail = NULL; + buf->free = NULL; + buf->memory_used = 0; + INIT_WORK(&buf->work, flush_to_ldisc); } -- cgit v1.2.2 From ecbbfd44a08fa80e0d664814efd4c187721b85f6 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Thu, 18 Oct 2012 22:26:47 +0200 Subject: TTY: move tty buffers to tty_port MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit So this is it. The big step why we did all the work over the past kernel releases. Now everything is prepared, so nothing protects us from doing that big step. | | \ \ nnnn/^l | | | | \ / / | | | '-,.__ => \/ ,-` => | '-,.__ | O __.´´) ( .` | O __.´´) ~~~ ~~ `` ~~~ ~~ The buffers are now in the tty_port structure and we can start teaching the buffer helpers (insert char/string, flip etc.) to use tty_port instead of tty_struct all around. Signed-off-by: Jiri Slaby Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 102 ++++++++++++++++++++++++----------------------- 1 file changed, 53 insertions(+), 49 deletions(-) (limited to 'drivers/tty/tty_buffer.c') diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index ddd74d41cbb2..06725f5cc819 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -27,9 +27,9 @@ * Locking: none */ -void tty_buffer_free_all(struct tty_struct *tty) +void tty_buffer_free_all(struct tty_port *port) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; struct tty_buffer *thead; while ((thead = buf->head) != NULL) { @@ -56,11 +56,11 @@ void tty_buffer_free_all(struct tty_struct *tty) * Locking: Caller must hold tty->buf.lock */ -static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size) +static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) { struct tty_buffer *p; - if (tty->buf.memory_used + size > 65536) + if (port->buf.memory_used + size > 65536) return NULL; p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); if (p == NULL) @@ -72,7 +72,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size) 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; + port->buf.memory_used += size; return p; } @@ -87,9 +87,9 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size) * Locking: Caller must hold tty->buf.lock */ -static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b) +static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; /* Dumb strategy for now - should keep some stats */ buf->memory_used -= b->size; @@ -114,14 +114,14 @@ static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b) * Locking: Caller must hold tty->buf.lock */ -static void __tty_buffer_flush(struct tty_struct *tty) +static void __tty_buffer_flush(struct tty_port *port) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; struct tty_buffer *thead; while ((thead = buf->head) != NULL) { buf->head = thead->next; - tty_buffer_free(tty, thead); + tty_buffer_free(port, thead); } buf->tail = NULL; } @@ -140,7 +140,7 @@ static void __tty_buffer_flush(struct tty_struct *tty) void tty_buffer_flush(struct tty_struct *tty) { struct tty_port *port = tty->port; - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; unsigned long flags; spin_lock_irqsave(&buf->lock, flags); @@ -155,7 +155,7 @@ void tty_buffer_flush(struct tty_struct *tty) test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0); return; } else - __tty_buffer_flush(tty); + __tty_buffer_flush(port); spin_unlock_irqrestore(&buf->lock, flags); } @@ -171,9 +171,9 @@ void tty_buffer_flush(struct tty_struct *tty) * Locking: Caller must hold tty->buf.lock */ -static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) +static struct tty_buffer *tty_buffer_find(struct tty_port *port, size_t size) { - struct tty_buffer **tbh = &tty->buf.free; + struct tty_buffer **tbh = &port->buf.free; while ((*tbh) != NULL) { struct tty_buffer *t = *tbh; if (t->size >= size) { @@ -182,14 +182,14 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) t->used = 0; t->commit = 0; t->read = 0; - tty->buf.memory_used += t->size; + port->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); + return tty_buffer_alloc(port, size); /* Should possibly check if this fails for the largest buffer we have queued and recycle that ? */ } @@ -200,11 +200,11 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size) * * Make at least size bytes of linear space available for the tty * buffer. If we fail return the size we managed to find. - * Locking: Caller must hold tty->buf.lock + * Locking: Caller must hold port->buf.lock */ -static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) +static int __tty_buffer_request_room(struct tty_port *port, size_t size) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; struct tty_buffer *b, *n; int left; /* OPTIMISATION: We could keep a per tty "zero" sized buffer to @@ -218,7 +218,7 @@ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) if (left < size) { /* This is the slow path - looking for new buffers to use */ - if ((n = tty_buffer_find(tty, size)) != NULL) { + if ((n = tty_buffer_find(port, size)) != NULL) { if (b != NULL) { b->next = n; b->commit = b->used; @@ -241,16 +241,17 @@ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size) * 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 + * Locking: Takes port->buf.lock */ int tty_buffer_request_room(struct tty_struct *tty, size_t size) { + struct tty_port *port = tty->port; unsigned long flags; int length; - spin_lock_irqsave(&tty->buf.lock, flags); - length = __tty_buffer_request_room(tty, size); - spin_unlock_irqrestore(&tty->buf.lock, flags); + spin_lock_irqsave(&port->buf.lock, flags); + length = __tty_buffer_request_room(port, size); + spin_unlock_irqrestore(&port->buf.lock, flags); return length; } EXPORT_SYMBOL_GPL(tty_buffer_request_room); @@ -265,13 +266,13 @@ EXPORT_SYMBOL_GPL(tty_buffer_request_room); * Queue a series of bytes to the tty buffering. All the characters * passed are marked with the supplied flag. Returns the number added. * - * Locking: Called functions may take tty->buf.lock + * Locking: Called functions may take port->buf.lock */ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty, const unsigned char *chars, char flag, size_t size) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; int copied = 0; do { int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); @@ -280,7 +281,7 @@ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty, struct tty_buffer *tb; spin_lock_irqsave(&buf->lock, flags); - space = __tty_buffer_request_room(tty, goal); + space = __tty_buffer_request_room(tty->port, goal); tb = buf->tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) { @@ -311,13 +312,13 @@ EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); * the flags array indicates the status of the character. Returns the * number added. * - * Locking: Called functions may take tty->buf.lock + * Locking: Called functions may take port->buf.lock */ int tty_insert_flip_string_flags(struct tty_struct *tty, const unsigned char *chars, const char *flags, size_t size) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; int copied = 0; do { int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); @@ -326,7 +327,7 @@ int tty_insert_flip_string_flags(struct tty_struct *tty, struct tty_buffer *tb; spin_lock_irqsave(&buf->lock, __flags); - space = __tty_buffer_request_room(tty, goal); + space = __tty_buffer_request_room(tty->port, goal); tb = buf->tail; /* If there is no space then tb may be NULL */ if (unlikely(space == 0)) { @@ -357,12 +358,12 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags); * Note that this function can only be used when the low_latency flag * is unset. Otherwise the workqueue won't be flushed. * - * Locking: Takes tty->buf.lock + * Locking: Takes port->buf.lock */ void tty_schedule_flip(struct tty_struct *tty) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; unsigned long flags; spin_lock_irqsave(&buf->lock, flags); @@ -385,19 +386,19 @@ EXPORT_SYMBOL(tty_schedule_flip); * 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 + * Locking: May call functions taking port->buf.lock */ int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, - size_t size) + size_t size) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; int space; unsigned long flags; struct tty_buffer *tb; spin_lock_irqsave(&buf->lock, flags); - space = __tty_buffer_request_room(tty, size); + space = __tty_buffer_request_room(tty->port, size); tb = buf->tail; if (likely(space)) { @@ -423,19 +424,19 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string); * 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 + * Locking: May call functions taking port->buf.lock */ int tty_prepare_flip_string_flags(struct tty_struct *tty, unsigned char **chars, char **flags, size_t size) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; int space; unsigned long __flags; struct tty_buffer *tb; spin_lock_irqsave(&buf->lock, __flags); - space = __tty_buffer_request_room(tty, size); + space = __tty_buffer_request_room(tty->port, size); tb = buf->tail; if (likely(space)) { @@ -464,13 +465,16 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); static void flush_to_ldisc(struct work_struct *work) { - struct tty_struct *tty = - container_of(work, struct tty_struct, buf.work); - struct tty_port *port = tty->port; - struct tty_bufhead *buf = &tty->buf; + struct tty_port *port = container_of(work, struct tty_port, buf.work); + struct tty_bufhead *buf = &port->buf; + struct tty_struct *tty; unsigned long flags; struct tty_ldisc *disc; + tty = port->itty; + if (WARN_RATELIMIT(tty == NULL, "tty is NULL")) + return; + disc = tty_ldisc_ref(tty); if (disc == NULL) /* !TTY_LDISC */ return; @@ -489,7 +493,7 @@ static void flush_to_ldisc(struct work_struct *work) if (head->next == NULL) break; buf->head = head->next; - tty_buffer_free(tty, head); + tty_buffer_free(port, head); continue; } /* Ldisc or user is trying to flush the buffers @@ -515,7 +519,7 @@ static void flush_to_ldisc(struct work_struct *work) /* 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(TTYP_FLUSHPENDING, &port->iflags)) { - __tty_buffer_flush(tty); + __tty_buffer_flush(port); clear_bit(TTYP_FLUSHPENDING, &port->iflags); wake_up(&tty->read_wait); } @@ -535,7 +539,7 @@ static void flush_to_ldisc(struct work_struct *work) void tty_flush_to_ldisc(struct tty_struct *tty) { if (!tty->low_latency) - flush_work(&tty->buf.work); + flush_work(&tty->port->buf.work); } /** @@ -553,7 +557,7 @@ void tty_flush_to_ldisc(struct tty_struct *tty) void tty_flip_buffer_push(struct tty_struct *tty) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &tty->port->buf; unsigned long flags; spin_lock_irqsave(&buf->lock, flags); @@ -578,9 +582,9 @@ EXPORT_SYMBOL(tty_flip_buffer_push); * Locking: none */ -void tty_buffer_init(struct tty_struct *tty) +void tty_buffer_init(struct tty_port *port) { - struct tty_bufhead *buf = &tty->buf; + struct tty_bufhead *buf = &port->buf; spin_lock_init(&buf->lock); buf->head = NULL; -- cgit v1.2.2 From b8b345bae8cb6745f2afdd28bb2d93f9cf0d7f2c Mon Sep 17 00:00:00 2001 From: Ivo Sieben Date: Wed, 24 Oct 2012 14:35:42 +0200 Subject: TTY: Report warning when low_latency flag is wrongly used When a driver has the low_latency flag set and uses the schedule_flip() function to initiate copying data to the line discipline, a workqueue is scheduled in but never actually flushed. This is incorrect use of the low_latency flag (driver should not support the low_latency flag, or use the tty_flip_buffer_push() function instead). Make sure a warning is reported to catch incorrect use of the low_latency flag. This patch goes with: cee4ad1ed90a0959fc29f9d30a2526e5e9522cfa Signed-off-by: Ivo Sieben Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/tty/tty_buffer.c') diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 06725f5cc819..6cf87d7afb7e 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -365,6 +365,7 @@ void tty_schedule_flip(struct tty_struct *tty) { struct tty_bufhead *buf = &tty->port->buf; unsigned long flags; + WARN_ON(tty->low_latency); spin_lock_irqsave(&buf->lock, flags); if (buf->tail != NULL) -- cgit v1.2.2