On Wed, Mar 22, 2017 at 07:08:46PM -0700, l...@pengaru.com wrote:
> Hello list,
>
> After approximately one day day of running 4.11.0-rc3 with 7e54d9d reverted to
> enable regular use, this happened upon destroying an xterm:
>
> [80817.525112] BUG: unable to handle kernel paging request at 0000000000002260
> [80817.525239] IP: n_tty_receive_buf_common+0x68/0xab0
> [80817.525312] PGD 0
>
> [80817.525387] Oops: 0000 [#1] PREEMPT SMP
> [80817.525452] CPU: 0 PID: 9532 Comm: kworker/u4:3 Not tainted
> 4.11.0-rc3-00001-gc56a355 #53
> [80817.525564] Hardware name: LENOVO 7668CTO/7668CTO, BIOS 7NETC2WW (2.22 )
> 03/22/2011
> [80817.525673] Workqueue: events_unbound flush_to_ldisc
> [80817.525752] task: ffff967d91d80000 task.stack: ffff9add81f40000
> [80817.525839] RIP: 0010:n_tty_receive_buf_common+0x68/0xab0
> [80817.525917] RSP: 0018:ffff9add81f43d38 EFLAGS: 00010297
> [80817.525992] RAX: 0000000000000000 RBX: ffff967d91c98c00 RCX:
> 0000000000000001
> [80817.526035] RDX: ffff967e73bba58d RSI: ffff967e73bba48d RDI:
> ffff967d91c98cc0
> [80817.526035] RBP: ffff9add81f43dd0 R08: 0000000000000001 R09:
> 0000000000000000
> [80817.526035] R10: 00004980cbe001e0 R11: 0000000000000000 R12:
> ffff967d87aacf20
> [80817.526035] R13: ffff967e73bba58d R14: 0000000000000001 R15:
> ffff967e74aa8008
> [80817.526035] FS: 0000000000000000(0000) GS:ffff967e7bc00000(0000)
> knlGS:0000000000000000
> [80817.526035] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [80817.526035] CR2: 0000000000002260 CR3: 0000000099009000 CR4:
> 00000000000006f0
> [80817.526035] Call Trace:
> [80817.526035] ? update_curr+0xbb/0x1a0
> [80817.526035] n_tty_receive_buf2+0xf/0x20
> [80817.526035] tty_ldisc_receive_buf+0x1d/0x50
> [80817.526035] tty_port_default_receive_buf+0x40/0x60
> [80817.526035] flush_to_ldisc+0x94/0xa0
> [80817.526035] process_one_work+0x13b/0x3e0
> [80817.526035] worker_thread+0x64/0x4a0
> [80817.526035] kthread+0x10f/0x150
> [80817.526035] ? process_one_work+0x3e0/0x3e0
> [80817.526035] ? __kthread_create_on_node+0x150/0x150
> [80817.526035] ret_from_fork+0x29/0x40
> [80817.526035] Code: 85 70 ff ff ff e8 59 75 57 00 48 8d 83 00 02 00 00 c7 45
> c8 00 00 00 00 48 89 45 98 48 8d 83 28 02 00 00 48 89 45 90 48 8b 45 b8 <48>
> 8b b0 60 22 00 00 48 8b 08 89 f0 29 c8 f6 83 10 01 00 00 08
> [80817.526035] RIP: n_tty_receive_buf_common+0x68/0xab0 RSP: ffff9add81f43d38
> [80817.526035] CR2: 0000000000002260
> [80817.526035] ---[ end trace 640aec4765d350f2 ]---
>
>
> That xterm process is stuck, and I am unable to start any new xterms,
> switching to virtual consoles proves useless, presumably there's an important
> lock held.
>
<snip>
At a casual glance of the v4.10..v4.11-rc3 changes affecting drivers/tty, the
commit c3485e looks suspicious to me, these hunks in particular:
@@ -465,16 +465,6 @@ static void flush_to_ldisc(struct work_struct *work)
{
struct tty_port *port = container_of(work, struct tty_port, buf.work);
struct tty_bufhead *buf = &port->buf;
- struct tty_struct *tty;
- struct tty_ldisc *disc;
-
- tty = READ_ONCE(port->itty);
- if (tty == NULL)
- return;
-
- disc = tty_ldisc_ref(tty);
- if (disc == NULL)
- return;
mutex_lock(&buf->lock);
@@ -504,7 +494,7 @@ static void flush_to_ldisc(struct work_struct *work)
continue;
}
- count = receive_buf(disc, head, count);
+ count = receive_buf(port, head, count);
if (!count)
break;
head->read += count;
@@ -512,7 +502,6 @@ static void flush_to_ldisc(struct work_struct *work)
mutex_unlock(&buf->lock);
- tty_ldisc_deref(disc);
}
/**
<snip>
I'm not familiar with this code at all, but port->buf is part of port, and if
the port is destroyed as part of the tty, then perhaps port->buf (and
port->buf->lock) may become invalid on us without these:
- tty = READ_ONCE(port->itty);
- if (tty == NULL)
- return;
-
- disc = tty_ldisc_ref(tty);
- if (disc == NULL)
- return;
Added Rob Herring, author of c3485ee to CC list.
Regards,
Vito Caputo
