* [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).
@ 2012-11-21 21:12 Ilya Zykov
2012-11-21 21:30 ` Alan Cox
0 siblings, 1 reply; 3+ messages in thread
From: Ilya Zykov @ 2012-11-21 21:12 UTC (permalink / raw)
To: Andrew McGregor, Greg Kroah-Hartman, Alan Cox, linux-kernel,
linux-serial
Revert 'tty: fix "IRQ45: nobody cared"'
This revert commit 7b292b4bf9a9d6098440d85616d6ca4c608b8304
Function reset_buffer_flags() also invoked during the
ioctl(...,TCFLSH,..). At the time of request we can have full buffers
and throttled driver too. If we don't unthrottle driver, we can get
forever throttled driver, because after request, we will have
empty buffers and throttled driver and there is no place to unthrottle driver.
It simple reproduce with "pty" pair then one side sleep on tty->write_wait,
and other side do ioctl(...,TCFLSH,..). Then there is no place to do writers wake up.
About 'tty: fix "IRQ45: nobody cared"':
We don't call tty_unthrottle() if release last filp - ('tty->count == 0')
In other case it must be safely. Maybe we have bug in other place.
Signed-off-by: Ilya Zykov <ilya@ilyx.ru>
---
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 26f0d0e..a783d0e 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -184,6 +184,7 @@ static void reset_buffer_flags(struct tty_struct *tty)
tty->canon_head = tty->canon_data = tty->erasing = 0;
memset(&tty->read_flags, 0, sizeof tty->read_flags);
n_tty_set_room(tty);
+ check_unthrottle(tty);
}
/**
@@ -1585,7 +1586,6 @@ static int n_tty_open(struct tty_struct *tty)
return -ENOMEM;
}
reset_buffer_flags(tty);
- tty_unthrottle(tty);
tty->column = 0;
n_tty_set_termios(tty, NULL);
tty->minimum_to_wake = 1;
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).
2012-11-21 21:12 [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..) Ilya Zykov
@ 2012-11-21 21:30 ` Alan Cox
0 siblings, 0 replies; 3+ messages in thread
From: Alan Cox @ 2012-11-21 21:30 UTC (permalink / raw)
To: Ilya Zykov
Cc: Andrew McGregor, Greg Kroah-Hartman, Alan Cox, linux-kernel,
linux-serial
> Function reset_buffer_flags() also invoked during the
> ioctl(...,TCFLSH,..). At the time of request we can have full buffers
> and throttled driver too. If we don't unthrottle driver, we can get
> forever throttled driver, because after request, we will have
> empty buffers and throttled driver and there is no place to unthrottle driver.
> It simple reproduce with "pty" pair then one side sleep on tty->write_wait,
> and other side do ioctl(...,TCFLSH,..). Then there is no place to do writers wake up.
So instead of revertng it why not just fix it ? Just add an argument to
the reset_buffer_flags function to indicate if unthrottling is permitted.
Alan
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).
2012-11-27 19:32 ` Alan Cox
@ 2013-01-16 9:07 ` Ilya Zykov
0 siblings, 0 replies; 3+ messages in thread
From: Ilya Zykov @ 2013-01-16 9:07 UTC (permalink / raw)
To: Alan Cox; +Cc: Greg Kroah-Hartman, Alan Cox, linux-serial, linux-kernel
Regression 'tty: fix "IRQ45: nobody cared"'
Regression commit 7b292b4bf9a9d6098440d85616d6ca4c608b8304
Function reset_buffer_flags() also invoked during the ioctl(...,TCFLSH,..).
At the time of request we can have full buffers and throttled driver too.
If we don't unthrottle driver, we can get forever throttled driver, because,
after request, we will have empty buffers and throttled driver and
there is no place to unthrottle driver.
It simple reproduce with "pty" pair then one side sleep on tty->write_wait,
and other side do ioctl(...,TCFLSH,..). Then there is no place to do writers wake up.
Signed-off-by: Ilya Zykov <ilya@ilyx.ru>
---
drivers/tty/tty_ioctl.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 8481b29..cc0fc52 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -1096,12 +1096,16 @@ int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
ld = tty_ldisc_ref_wait(tty);
switch (arg) {
case TCIFLUSH:
- if (ld && ld->ops->flush_buffer)
+ if (ld && ld->ops->flush_buffer) {
ld->ops->flush_buffer(tty);
+ tty_unthrottle(tty);
+ }
break;
case TCIOFLUSH:
- if (ld && ld->ops->flush_buffer)
+ if (ld && ld->ops->flush_buffer) {
ld->ops->flush_buffer(tty);
+ tty_unthrottle(tty);
+ }
/* fall through */
case TCOFLUSH:
tty_driver_flush_buffer(tty);
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-01-16 9:07 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2012-11-21 21:12 [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..) Ilya Zykov
2012-11-21 21:30 ` Alan Cox
-- strict thread matches above, loose matches on Subject: below --
2012-11-27 6:14 [PATCH v4] " Ilya Zykov
2012-11-27 17:24 ` Greg Kroah-Hartman
2012-11-27 18:46 ` Ilya Zykov
2012-11-27 19:32 ` Alan Cox
2013-01-16 9:07 ` [PATCH] " Ilya Zykov
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).