diff options
| author | Alan Cox <alan@redhat.com> | 2007-07-15 23:39:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-16 09:05:41 -0700 |
| commit | 9c1729db3e6d738f872bcb090212af00473bf666 (patch) | |
| tree | be68b99784607953fb50d9330d34c2728215be57 /drivers/char/n_hdlc.c | |
| parent | c9c64155f5a81b4b41e98f9fb9c464a565c1bf72 (diff) | |
| download | lwn-9c1729db3e6d738f872bcb090212af00473bf666.tar.gz lwn-9c1729db3e6d738f872bcb090212af00473bf666.zip | |
Prevent an O_NDELAY writer from blocking when a tty write is blocked by the tty atomic writer mutex
Without this a tty write could block if a previous blocking tty write was
in progress on the same tty and blocked by a line discipline or hardware
event. Originally found and reported by Dave Johnson.
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Dave Johnson <djohnson+linux-kernel@sw.starentnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/char/n_hdlc.c')
| -rw-r--r-- | drivers/char/n_hdlc.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/char/n_hdlc.c b/drivers/char/n_hdlc.c index 337a87f86a3b..37f7d3403040 100644 --- a/drivers/char/n_hdlc.c +++ b/drivers/char/n_hdlc.c @@ -780,13 +780,14 @@ static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp, poll_wait(filp, &tty->write_wait, wait); /* set bits for operations that won't block */ - if(n_hdlc->rx_buf_list.head) + if (n_hdlc->rx_buf_list.head) mask |= POLLIN | POLLRDNORM; /* readable */ if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) mask |= POLLHUP; - if(tty_hung_up_p(filp)) + if (tty_hung_up_p(filp)) mask |= POLLHUP; - if(n_hdlc->tx_free_buf_list.head) + if (!tty_is_writelocked(tty) && + n_hdlc->tx_free_buf_list.head) mask |= POLLOUT | POLLWRNORM; /* writable */ } return mask; @@ -861,7 +862,7 @@ static void n_hdlc_buf_put(struct n_hdlc_buf_list *list, spin_lock_irqsave(&list->spinlock,flags); buf->link=NULL; - if(list->tail) + if (list->tail) list->tail->link = buf; else list->head = buf; |