Instrumented testing shows a tty can be hungup multiple times [1].
Although concurrent hangups are properly serialized, multiple
hangups for the same tty should be prevented.
If tty has already been HUPPED, abort hangup. Note it is not
necessary to cleanup file *redirect on subsequent hangups,
as only TIOCCONS can set that value and ioctls are disabled
after hangup.
Signed-off-by: Peter Hurley <[email protected]>
[1]
Test performed by simulating a concurrent async hangup via
tty_hangup() with a sync hangup via tty_vhangup(), while
__tty_hangup() was instrumented with:
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 26bb78c..fe8b061 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -629,6 +629,8 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
tty_lock(tty);
+ WARN_ON(test_bit(TTY_HUPPED, &tty->flags));
+
/* some functions below drop BTM, so we need this bit */
set_bit(TTY_HUPPING, &tty->flags);
Test result:
WARNING: at /home/peter/src/kernels/mainline/drivers/tty/tty_io.c:632 __tty_hangup+0x459/0x460()
Modules linked in: ip6table_filter ip6_tables ebtable_nat <...snip...>
CPU: 6 PID: 1197 Comm: kworker/6:2 Not tainted 3.10.0-0+rfcomm-xeon #0+rfcomm
Hardware name: Dell Inc. Precision WorkStation T5400 /0RW203, BIOS A11 04/30/2012
Workqueue: events do_tty_hangup
0000000000000009 ffff8802b16d7d18 ffffffff816b553e ffff8802b16d7d58
ffffffff810407e0 ffff880254f95c00 ffff880254f95c00 ffff8802bfd92b00
ffff8802bfd96b00 ffff880254f95e40 0000000000000180 ffff8802b16d7d68
Call Trace:
[<ffffffff816b553e>] dump_stack+0x19/0x1b
[<ffffffff810407e0>] warn_slowpath_common+0x70/0xa0
[<ffffffff8104082a>] warn_slowpath_null+0x1a/0x20
[<ffffffff813fb279>] __tty_hangup+0x459/0x460
[<ffffffff8107409c>] ? finish_task_switch+0xbc/0xe0
[<ffffffff813fb297>] do_tty_hangup+0x17/0x20
[<ffffffff8105fd6f>] process_one_work+0x16f/0x450
[<ffffffff8106007c>] process_scheduled_works+0x2c/0x40
[<ffffffff8106060a>] worker_thread+0x26a/0x380
[<ffffffff810603a0>] ? rescuer_thread+0x310/0x310
[<ffffffff810698a0>] kthread+0xc0/0xd0
[<ffffffff816b0000>] ? destroy_compound_page+0x65/0x92
[<ffffffff810697e0>] ? kthread_create_on_node+0x130/0x130
[<ffffffff816c495c>] ret_from_fork+0x7c/0xb0
[<ffffffff810697e0>] ? kthread_create_on_node+0x130/0x130
---[ end trace 98d9f01536cf411e ]---
---
drivers/tty/tty_io.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 26bb78c..a9355ce 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -629,6 +629,11 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
tty_lock(tty);
+ if (test_bit(TTY_HUPPED, &tty->flags)) {
+ tty_unlock(tty);
+ return;
+ }
+
/* some functions below drop BTM, so we need this bit */
set_bit(TTY_HUPPING, &tty->flags);
--
1.8.1.2
On Wed, Jul 31, 2013 at 02:05:45PM -0400, Peter Hurley wrote:
> Instrumented testing shows a tty can be hungup multiple times [1].
> Although concurrent hangups are properly serialized, multiple
> hangups for the same tty should be prevented.
>
> If tty has already been HUPPED, abort hangup. Note it is not
> necessary to cleanup file *redirect on subsequent hangups,
> as only TIOCCONS can set that value and ioctls are disabled
> after hangup.
>
> Signed-off-by: Peter Hurley <[email protected]>
>
> [1]
> Test performed by simulating a concurrent async hangup via
> tty_hangup() with a sync hangup via tty_vhangup(), while
> __tty_hangup() was instrumented with:
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 26bb78c..fe8b061 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -629,6 +629,8 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
>
> tty_lock(tty);
>
> + WARN_ON(test_bit(TTY_HUPPED, &tty->flags));
> +
> /* some functions below drop BTM, so we need this bit */
> set_bit(TTY_HUPPING, &tty->flags);
>
> Test result:
>
> WARNING: at /home/peter/src/kernels/mainline/drivers/tty/tty_io.c:632 __tty_hangup+0x459/0x460()
> Modules linked in: ip6table_filter ip6_tables ebtable_nat <...snip...>
> CPU: 6 PID: 1197 Comm: kworker/6:2 Not tainted 3.10.0-0+rfcomm-xeon #0+rfcomm
> Hardware name: Dell Inc. Precision WorkStation T5400 /0RW203, BIOS A11 04/30/2012
> Workqueue: events do_tty_hangup
> 0000000000000009 ffff8802b16d7d18 ffffffff816b553e ffff8802b16d7d58
> ffffffff810407e0 ffff880254f95c00 ffff880254f95c00 ffff8802bfd92b00
> ffff8802bfd96b00 ffff880254f95e40 0000000000000180 ffff8802b16d7d68
> Call Trace:
> [<ffffffff816b553e>] dump_stack+0x19/0x1b
> [<ffffffff810407e0>] warn_slowpath_common+0x70/0xa0
> [<ffffffff8104082a>] warn_slowpath_null+0x1a/0x20
> [<ffffffff813fb279>] __tty_hangup+0x459/0x460
> [<ffffffff8107409c>] ? finish_task_switch+0xbc/0xe0
> [<ffffffff813fb297>] do_tty_hangup+0x17/0x20
> [<ffffffff8105fd6f>] process_one_work+0x16f/0x450
> [<ffffffff8106007c>] process_scheduled_works+0x2c/0x40
> [<ffffffff8106060a>] worker_thread+0x26a/0x380
> [<ffffffff810603a0>] ? rescuer_thread+0x310/0x310
> [<ffffffff810698a0>] kthread+0xc0/0xd0
> [<ffffffff816b0000>] ? destroy_compound_page+0x65/0x92
> [<ffffffff810697e0>] ? kthread_create_on_node+0x130/0x130
> [<ffffffff816c495c>] ret_from_fork+0x7c/0xb0
> [<ffffffff810697e0>] ? kthread_create_on_node+0x130/0x130
> ---[ end trace 98d9f01536cf411e ]---
> ---
> drivers/tty/tty_io.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
> index 26bb78c..a9355ce 100644
> --- a/drivers/tty/tty_io.c
> +++ b/drivers/tty/tty_io.c
> @@ -629,6 +629,11 @@ static void __tty_hangup(struct tty_struct *tty, int exit_session)
>
> tty_lock(tty);
>
> + if (test_bit(TTY_HUPPED, &tty->flags)) {
> + tty_unlock(tty);
> + return;
> + }
> +
> /* some functions below drop BTM, so we need this bit */
> set_bit(TTY_HUPPING, &tty->flags);
A diff inside the changelog entry of a diff is going to cause havoc :)
I'll go edit this to make it not complain...
thanks,
greg k-h
On 08/01/2013 11:46 PM, Greg Kroah-Hartman wrote:
> A diff inside the changelog entry of a diff is going to cause havoc :)
Right, sorry :) Won't happen again.
> I'll go edit this to make it not complain...
Thanks,
Peter Hurley