diff options
| author | Peter Hurley | 2014-05-02 10:56:11 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2014-05-03 18:14:28 -0400 |
| commit | 5fbf1a65dd53ef313783c34a0e93a6e29def6136 (patch) | |
| tree | e4631779d08d03cd27d0b4a5546e4a5768a77ead | |
| parent | 501fed45b7e8836ee9373f4d31e2d85e3db6103a (diff) | |
Revert "tty: Fix race condition between __tty_buffer_request_room and flush_to_ldisc"
This reverts commit 6a20dbd6caa2358716136144bf524331d70b1e03.
Although the commit correctly identifies an unsafe race condition
between __tty_buffer_request_room() and flush_to_ldisc(), the commit
fixes the race with an unnecessary spinlock in a lockless algorithm.
The follow-on commit, "tty: Fix lockless tty buffer race" fixes
the race locklessly.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_buffer.c | 16 | ||||
| -rw-r--r-- | include/linux/tty.h | 1 |
2 files changed, 2 insertions, 15 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index f1d30f6945af..8ebd9f88a6f6 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -255,16 +255,11 @@ static int __tty_buffer_request_room(struct tty_port *port, size_t size, if (change || left < size) { /* This is the slow path - looking for new buffers to use */ if ((n = tty_buffer_alloc(port, size)) != NULL) { - unsigned long iflags; - n->flags = flags; buf->tail = n; - - spin_lock_irqsave(&buf->flush_lock, iflags); b->commit = b->used; + smp_mb(); b->next = n; - spin_unlock_irqrestore(&buf->flush_lock, iflags); - } else if (change) size = 0; else @@ -448,7 +443,6 @@ static void flush_to_ldisc(struct work_struct *work) mutex_lock(&buf->lock); while (1) { - unsigned long flags; struct tty_buffer *head = buf->head; int count; @@ -456,19 +450,14 @@ static void flush_to_ldisc(struct work_struct *work) if (atomic_read(&buf->priority)) break; - spin_lock_irqsave(&buf->flush_lock, flags); count = head->commit - head->read; if (!count) { - if (head->next == NULL) { - spin_unlock_irqrestore(&buf->flush_lock, flags); + if (head->next == NULL) break; - } buf->head = head->next; - spin_unlock_irqrestore(&buf->flush_lock, flags); tty_buffer_free(port, head); continue; } - spin_unlock_irqrestore(&buf->flush_lock, flags); count = receive_buf(tty, head, count); if (!count) @@ -523,7 +512,6 @@ void tty_buffer_init(struct tty_port *port) struct tty_bufhead *buf = &port->buf; mutex_init(&buf->lock); - spin_lock_init(&buf->flush_lock); tty_buffer_reset(&buf->sentinel, 0); buf->head = &buf->sentinel; buf->tail = &buf->sentinel; diff --git a/include/linux/tty.h b/include/linux/tty.h index 036cccd80d9f..1c3316a47d7e 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -61,7 +61,6 @@ struct tty_bufhead { struct tty_buffer *head; /* Queue head */ struct work_struct work; struct mutex lock; - spinlock_t flush_lock; atomic_t priority; struct tty_buffer sentinel; struct llist_head free; /* Free queue head */ |