* [vfs/tty] possible circular locking dependency detected
@ 2008-05-12 18:32 Marcin Slusarz
2008-05-14 1:47 ` Andrew Morton
0 siblings, 1 reply; 4+ messages in thread
From: Marcin Slusarz @ 2008-05-12 18:32 UTC (permalink / raw)
To: LKML; +Cc: Alan Cox, Alexander Viro
May 11 08:52:08 [kernel] [ 21.052750] Clocksource tsc unstable (delta = -109466779 ns)
May 11 09:42:27 [kernel] [ 1104.496819] rarian-sk-get-c[5630]: segfault at 0 ip 7f478556caf0 sp 7fff8e3fe338 error 4 in libc-2.6.1.so[7f47854f9000+136000]
May 11 10:59:48 [kernel] [ 2494.165792]
May 11 10:59:48 [kernel] [ 2494.165794] =======================================================
May 11 10:59:48 [kernel] [ 2494.165801] [ INFO: possible circular locking dependency detected ]
May 11 10:59:48 [kernel] [ 2494.165805] 2.6.26-rc1-00007-g91b3a7a #217
May 11 10:59:48 [kernel] [ 2494.165807] -------------------------------------------------------
May 11 10:59:48 [kernel] [ 2494.165809] less/7053 is trying to acquire lock:
May 11 10:59:48 [kernel] [ 2494.165812] (tasklist_lock){..??}, at: [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
May 11 10:59:48 [kernel] [ 2494.165821]
May 11 10:59:48 [kernel] [ 2494.165822] but task is already holding lock:
May 11 10:59:48 [kernel] [ 2494.165824] (&tty->ctrl_lock){....}, at: [<ffffffff803d5f31>] tty_check_change+0x61/0x110
May 11 10:59:48 [kernel] [ 2494.165831]
May 11 10:59:48 [kernel] [ 2494.165832] which lock already depends on the new lock.
May 11 10:59:48 [kernel] [ 2494.165833]
May 11 10:59:48 [kernel] [ 2494.165835]
May 11 10:59:48 [kernel] [ 2494.165836] the existing dependency chain (in reverse order) is:
May 11 10:59:48 [kernel] [ 2494.165838]
May 11 10:59:48 [kernel] [ 2494.165839] -> #2 (&tty->ctrl_lock){....}:
May 11 10:59:48 [kernel] [ 2494.165843] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
May 11 10:59:48 [kernel] [ 2494.165851] [<ffffffff80253922>] lock_acquire+0x92/0xc0
May 11 10:59:48 [kernel] [ 2494.165858] [<ffffffff804deee0>] _spin_lock_irqsave+0x40/0x60
May 11 10:59:48 [kernel] [ 2494.165866] [<ffffffff803d31b5>] __proc_set_tty+0x35/0xe0
May 11 10:59:48 [kernel] [ 2494.165873] [<ffffffff803d76d4>] tty_ioctl+0xbf4/0xfe0
May 11 10:59:48 [kernel] [ 2494.165880] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
May 11 10:59:48 [kernel] [ 2494.165888] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
May 11 10:59:48 [kernel] [ 2494.165895] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
May 11 10:59:48 [kernel] [ 2494.165902] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
May 11 10:59:48 [kernel] [ 2494.165910] [<ffffffffffffffff>] 0xffffffffffffffff
May 11 10:59:48 [kernel] [ 2494.165924]
May 11 10:59:48 [kernel] [ 2494.165925] -> #1 (&sighand->siglock){++..}:
May 11 10:59:48 [kernel] [ 2494.165929] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
May 11 10:59:48 [kernel] [ 2494.165936] [<ffffffff80253922>] lock_acquire+0x92/0xc0
May 11 10:59:48 [kernel] [ 2494.165943] [<ffffffff804dec1f>] _spin_lock+0x2f/0x40
May 11 10:59:48 [kernel] [ 2494.165951] [<ffffffff8022d5a3>] copy_process+0x973/0x1210
May 11 10:59:48 [kernel] [ 2494.165959] [<ffffffff8022df12>] do_fork+0x82/0x2f0
May 11 10:59:48 [kernel] [ 2494.165967] [<ffffffff8020bfe1>] kernel_thread+0x81/0xde
May 11 10:59:48 [kernel] [ 2494.165974] [<ffffffff8020c048>] child_rip+0xa/0x12
May 11 10:59:48 [kernel] [ 2494.165981] [<ffffffffffffffff>] 0xffffffffffffffff
May 11 10:59:48 [kernel] [ 2494.166038]
May 11 10:59:48 [kernel] [ 2494.166039] -> #0 (tasklist_lock){..??}:
May 11 10:59:48 [kernel] [ 2494.166043] [<ffffffff802535ab>] __lock_acquire+0xd9b/0x1080
May 11 10:59:48 [kernel] [ 2494.166050] [<ffffffff80253922>] lock_acquire+0x92/0xc0
May 11 10:59:48 [kernel] [ 2494.166057] [<ffffffff804dede2>] _read_lock+0x32/0x50
May 11 10:59:48 [kernel] [ 2494.166063] [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
May 11 10:59:48 [kernel] [ 2494.166071] [<ffffffff803d5f80>] tty_check_change+0xb0/0x110
May 11 10:59:48 [kernel] [ 2494.166078] [<ffffffff803dac5f>] set_termios+0x1f/0x4c0
May 11 10:59:48 [kernel] [ 2494.166085] [<ffffffff803db379>] tty_mode_ioctl+0x279/0x3e0
May 11 10:59:48 [kernel] [ 2494.166092] [<ffffffff803db51d>] n_tty_ioctl+0x3d/0x260
May 11 10:59:48 [kernel] [ 2494.166100] [<ffffffff803d6c34>] tty_ioctl+0x154/0xfe0
May 11 10:59:48 [kernel] [ 2494.166107] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
May 11 10:59:48 [kernel] [ 2494.166114] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
May 11 10:59:48 [kernel] [ 2494.166121] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
May 11 10:59:48 [kernel] [ 2494.166128] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
May 11 10:59:48 [kernel] [ 2494.166135] [<ffffffffffffffff>] 0xffffffffffffffff
May 11 10:59:48 [kernel] [ 2494.166142]
May 11 10:59:48 [kernel] [ 2494.166143] other info that might help us debug this:
May 11 10:59:48 [kernel] [ 2494.166144]
May 11 10:59:48 [kernel] [ 2494.166146] 1 lock held by less/7053:
May 11 10:59:48 [kernel] [ 2494.166148] #0: (&tty->ctrl_lock){....}, at: [<ffffffff803d5f31>] tty_check_change+0x61/0x110
May 11 10:59:48 [kernel] [ 2494.166155]
May 11 10:59:48 [kernel] [ 2494.166156] stack backtrace:
May 11 10:59:48 [kernel] [ 2494.166159] Pid: 7053, comm: less Not tainted 2.6.26-rc1-00007-g91b3a7a #217
May 11 10:59:48 [kernel] [ 2494.166161]
May 11 10:59:48 [kernel] [ 2494.166162] Call Trace:
May 11 10:59:48 [kernel] [ 2494.166168] [<ffffffff80251223>] print_circular_bug_tail+0x83/0x90
May 11 10:59:48 [kernel] [ 2494.166172] [<ffffffff80250889>] ? print_circular_bug_entry+0x49/0x60
May 11 10:59:48 [kernel] [ 2494.166178] [<ffffffff802535ab>] __lock_acquire+0xd9b/0x1080
May 11 10:59:48 [kernel] [ 2494.166184] [<ffffffff80232e95>] ? is_current_pgrp_orphaned+0x15/0x50
May 11 10:59:48 [kernel] [ 2494.166189] [<ffffffff80253922>] lock_acquire+0x92/0xc0
May 11 10:59:48 [kernel] [ 2494.166206] [<ffffffff803d5f80>] tty_check_change+0xb0/0x110
May 11 10:59:48 [kernel] [ 2494.166211] [<ffffffff803dac5f>] set_termios+0x1f/0x4c0
May 11 10:59:48 [kernel] [ 2494.166216] [<ffffffff803d3423>] ? tty_ldisc_try+0x23/0x60
May 11 10:59:48 [kernel] [ 2494.166220] [<ffffffff803d3444>] ? tty_ldisc_try+0x44/0x60
May 11 10:59:48 [kernel] [ 2494.166224] [<ffffffff804df2c5>] ? _spin_unlock_irqrestore+0x65/0x80
May 11 10:59:48 [kernel] [ 2494.166230] [<ffffffff803db379>] tty_mode_ioctl+0x279/0x3e0
May 11 10:59:48 [kernel] [ 2494.166234] [<ffffffff803d3444>] ? tty_ldisc_try+0x44/0x60
May 11 10:59:48 [kernel] [ 2494.166239] [<ffffffff803db51d>] n_tty_ioctl+0x3d/0x260
May 11 10:59:48 [kernel] [ 2494.166244] [<ffffffff803d6c34>] tty_ioctl+0x154/0xfe0
May 11 10:59:48 [kernel] [ 2494.166249] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
May 11 10:59:48 [kernel] [ 2494.166256] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
May 11 10:59:48 [kernel] [ 2494.166263] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
May 11 10:59:48 [kernel] [ 2494.166269] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
May 11 10:59:48 [kernel] [ 2494.166274] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
May 11 10:59:48 [kernel] [ 2494.166280] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
May 11 10:59:48 [kernel] [ 2494.166286] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
May 11 10:59:48 [kernel] [ 2494.166292]
It was on 2.6.26-rc1 + some patches (afa26be86b65a7183ceac29bdf1f51d6fc6932f0)
I think it had something to do with a hang of my yakuake (KDE terminal emulator) session.
But I'm not sure (I noticed this warning much later)
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [vfs/tty] possible circular locking dependency detected
2008-05-12 18:32 [vfs/tty] possible circular locking dependency detected Marcin Slusarz
@ 2008-05-14 1:47 ` Andrew Morton
2008-05-14 15:39 ` Oleg Nesterov
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Morton @ 2008-05-14 1:47 UTC (permalink / raw)
To: Marcin Slusarz; +Cc: LKML, Alan Cox, Alexander Viro, Oleg Nesterov
On Mon, 12 May 2008 20:32:59 +0200 Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> May 11 08:52:08 [kernel] [ 21.052750] Clocksource tsc unstable (delta = -109466779 ns)
> May 11 09:42:27 [kernel] [ 1104.496819] rarian-sk-get-c[5630]: segfault at 0 ip 7f478556caf0 sp 7fff8e3fe338 error 4 in libc-2.6.1.so[7f47854f9000+136000]
> May 11 10:59:48 [kernel] [ 2494.165792]
> May 11 10:59:48 [kernel] [ 2494.165794] =======================================================
> May 11 10:59:48 [kernel] [ 2494.165801] [ INFO: possible circular locking dependency detected ]
> May 11 10:59:48 [kernel] [ 2494.165805] 2.6.26-rc1-00007-g91b3a7a #217
> May 11 10:59:48 [kernel] [ 2494.165807] -------------------------------------------------------
> May 11 10:59:48 [kernel] [ 2494.165809] less/7053 is trying to acquire lock:
> May 11 10:59:48 [kernel] [ 2494.165812] (tasklist_lock){..??}, at: [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
> May 11 10:59:48 [kernel] [ 2494.165821]
> May 11 10:59:48 [kernel] [ 2494.165822] but task is already holding lock:
> May 11 10:59:48 [kernel] [ 2494.165824] (&tty->ctrl_lock){....}, at: [<ffffffff803d5f31>] tty_check_change+0x61/0x110
> May 11 10:59:48 [kernel] [ 2494.165831]
> May 11 10:59:48 [kernel] [ 2494.165832] which lock already depends on the new lock.
> May 11 10:59:48 [kernel] [ 2494.165833]
> May 11 10:59:48 [kernel] [ 2494.165835]
> May 11 10:59:48 [kernel] [ 2494.165836] the existing dependency chain (in reverse order) is:
> May 11 10:59:48 [kernel] [ 2494.165838]
> May 11 10:59:48 [kernel] [ 2494.165839] -> #2 (&tty->ctrl_lock){....}:
> May 11 10:59:48 [kernel] [ 2494.165843] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
> May 11 10:59:48 [kernel] [ 2494.165851] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> May 11 10:59:48 [kernel] [ 2494.165858] [<ffffffff804deee0>] _spin_lock_irqsave+0x40/0x60
> May 11 10:59:48 [kernel] [ 2494.165866] [<ffffffff803d31b5>] __proc_set_tty+0x35/0xe0
> May 11 10:59:48 [kernel] [ 2494.165873] [<ffffffff803d76d4>] tty_ioctl+0xbf4/0xfe0
> May 11 10:59:48 [kernel] [ 2494.165880] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
> May 11 10:59:48 [kernel] [ 2494.165888] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
> May 11 10:59:48 [kernel] [ 2494.165895] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
> May 11 10:59:48 [kernel] [ 2494.165902] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
> May 11 10:59:48 [kernel] [ 2494.165910] [<ffffffffffffffff>] 0xffffffffffffffff
> May 11 10:59:48 [kernel] [ 2494.165924]
> May 11 10:59:48 [kernel] [ 2494.165925] -> #1 (&sighand->siglock){++..}:
> May 11 10:59:48 [kernel] [ 2494.165929] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
> May 11 10:59:48 [kernel] [ 2494.165936] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> May 11 10:59:48 [kernel] [ 2494.165943] [<ffffffff804dec1f>] _spin_lock+0x2f/0x40
> May 11 10:59:48 [kernel] [ 2494.165951] [<ffffffff8022d5a3>] copy_process+0x973/0x1210
> May 11 10:59:48 [kernel] [ 2494.165959] [<ffffffff8022df12>] do_fork+0x82/0x2f0
> May 11 10:59:48 [kernel] [ 2494.165967] [<ffffffff8020bfe1>] kernel_thread+0x81/0xde
> May 11 10:59:48 [kernel] [ 2494.165974] [<ffffffff8020c048>] child_rip+0xa/0x12
> May 11 10:59:48 [kernel] [ 2494.165981] [<ffffffffffffffff>] 0xffffffffffffffff
> May 11 10:59:48 [kernel] [ 2494.166038]
> May 11 10:59:48 [kernel] [ 2494.166039] -> #0 (tasklist_lock){..??}:
> May 11 10:59:48 [kernel] [ 2494.166043] [<ffffffff802535ab>] __lock_acquire+0xd9b/0x1080
> May 11 10:59:48 [kernel] [ 2494.166050] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> May 11 10:59:48 [kernel] [ 2494.166057] [<ffffffff804dede2>] _read_lock+0x32/0x50
> May 11 10:59:48 [kernel] [ 2494.166063] [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
> May 11 10:59:48 [kernel] [ 2494.166071] [<ffffffff803d5f80>] tty_check_change+0xb0/0x110
> May 11 10:59:48 [kernel] [ 2494.166078] [<ffffffff803dac5f>] set_termios+0x1f/0x4c0
> May 11 10:59:48 [kernel] [ 2494.166085] [<ffffffff803db379>] tty_mode_ioctl+0x279/0x3e0
> May 11 10:59:48 [kernel] [ 2494.166092] [<ffffffff803db51d>] n_tty_ioctl+0x3d/0x260
> May 11 10:59:48 [kernel] [ 2494.166100] [<ffffffff803d6c34>] tty_ioctl+0x154/0xfe0
> May 11 10:59:48 [kernel] [ 2494.166107] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
> May 11 10:59:48 [kernel] [ 2494.166114] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
> May 11 10:59:48 [kernel] [ 2494.166121] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
> May 11 10:59:48 [kernel] [ 2494.166128] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
> May 11 10:59:48 [kernel] [ 2494.166135] [<ffffffffffffffff>] 0xffffffffffffffff
> May 11 10:59:48 [kernel] [ 2494.166142]
> May 11 10:59:48 [kernel] [ 2494.166143] other info that might help us debug this:
> May 11 10:59:48 [kernel] [ 2494.166144]
> May 11 10:59:48 [kernel] [ 2494.166146] 1 lock held by less/7053:
> May 11 10:59:48 [kernel] [ 2494.166148] #0: (&tty->ctrl_lock){....}, at: [<ffffffff803d5f31>] tty_check_change+0x61/0x110
> May 11 10:59:48 [kernel] [ 2494.166155]
> May 11 10:59:48 [kernel] [ 2494.166156] stack backtrace:
> May 11 10:59:48 [kernel] [ 2494.166159] Pid: 7053, comm: less Not tainted 2.6.26-rc1-00007-g91b3a7a #217
> May 11 10:59:48 [kernel] [ 2494.166161]
> May 11 10:59:48 [kernel] [ 2494.166162] Call Trace:
> May 11 10:59:48 [kernel] [ 2494.166168] [<ffffffff80251223>] print_circular_bug_tail+0x83/0x90
> May 11 10:59:48 [kernel] [ 2494.166172] [<ffffffff80250889>] ? print_circular_bug_entry+0x49/0x60
> May 11 10:59:48 [kernel] [ 2494.166178] [<ffffffff802535ab>] __lock_acquire+0xd9b/0x1080
> May 11 10:59:48 [kernel] [ 2494.166184] [<ffffffff80232e95>] ? is_current_pgrp_orphaned+0x15/0x50
> May 11 10:59:48 [kernel] [ 2494.166189] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> May 11 10:59:48 [kernel] [ 2494.166206] [<ffffffff803d5f80>] tty_check_change+0xb0/0x110
> May 11 10:59:48 [kernel] [ 2494.166211] [<ffffffff803dac5f>] set_termios+0x1f/0x4c0
> May 11 10:59:48 [kernel] [ 2494.166216] [<ffffffff803d3423>] ? tty_ldisc_try+0x23/0x60
> May 11 10:59:48 [kernel] [ 2494.166220] [<ffffffff803d3444>] ? tty_ldisc_try+0x44/0x60
> May 11 10:59:48 [kernel] [ 2494.166224] [<ffffffff804df2c5>] ? _spin_unlock_irqrestore+0x65/0x80
> May 11 10:59:48 [kernel] [ 2494.166230] [<ffffffff803db379>] tty_mode_ioctl+0x279/0x3e0
> May 11 10:59:48 [kernel] [ 2494.166234] [<ffffffff803d3444>] ? tty_ldisc_try+0x44/0x60
> May 11 10:59:48 [kernel] [ 2494.166239] [<ffffffff803db51d>] n_tty_ioctl+0x3d/0x260
> May 11 10:59:48 [kernel] [ 2494.166244] [<ffffffff803d6c34>] tty_ioctl+0x154/0xfe0
> May 11 10:59:48 [kernel] [ 2494.166249] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
> May 11 10:59:48 [kernel] [ 2494.166256] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
> May 11 10:59:48 [kernel] [ 2494.166263] [<ffffffff80252baa>] ? __lock_acquire+0x39a/0x1080
> May 11 10:59:48 [kernel] [ 2494.166269] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
> May 11 10:59:48 [kernel] [ 2494.166274] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
> May 11 10:59:48 [kernel] [ 2494.166280] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
> May 11 10:59:48 [kernel] [ 2494.166286] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
> May 11 10:59:48 [kernel] [ 2494.166292]
>
> It was on 2.6.26-rc1 + some patches (afa26be86b65a7183ceac29bdf1f51d6fc6932f0)
> I think it had something to do with a hang of my yakuake (KDE terminal emulator) session.
> But I'm not sure (I noticed this warning much later)
Bummer.
I don't immediately see any reason why the ctrl_lock coverage in
tty_check_change() needs to be as broad as it is? But then it's one of
those super-secret-who-knows-what-it-does locks :( It seems to be
protecting ->session and ->pgrp.
This, perhaps...
--- a/drivers/char/tty_io.c~a
+++ a/drivers/char/tty_io.c
@@ -1215,10 +1215,11 @@ int tty_check_change(struct tty_struct *
if (!tty->pgrp) {
printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
- goto out;
+ goto out_unlock;
}
if (task_pgrp(current) == tty->pgrp)
- goto out;
+ goto out_unlock;
+ spin_unlock_irqrestore(&tty->ctrl_lock, flags);
if (is_ignored(SIGTTOU))
goto out;
if (is_current_pgrp_orphaned()) {
@@ -1229,6 +1230,8 @@ int tty_check_change(struct tty_struct *
set_thread_flag(TIF_SIGPENDING);
ret = -ERESTARTSYS;
out:
+ return ret;
+out_unlock:
spin_unlock_irqrestore(&tty->ctrl_lock, flags);
return ret;
}
_
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [vfs/tty] possible circular locking dependency detected
2008-05-14 1:47 ` Andrew Morton
@ 2008-05-14 15:39 ` Oleg Nesterov
2008-05-15 16:27 ` [PATCH] tty_check_change-avoid-taking-tasklist_lock-while-holding-tty-ctrl_lock-simplify Oleg Nesterov
0 siblings, 1 reply; 4+ messages in thread
From: Oleg Nesterov @ 2008-05-14 15:39 UTC (permalink / raw)
To: Andrew Morton
Cc: Marcin Slusarz, LKML, Alan Cox, Alexander Viro, Peter Zijlstra
On 05/13, Andrew Morton wrote:
>
> On Mon, 12 May 2008 20:32:59 +0200 Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
>
> > May 11 10:59:48 [kernel] [ 2494.165794] =======================================================
> > May 11 10:59:48 [kernel] [ 2494.165801] [ INFO: possible circular locking dependency detected ]
> > May 11 10:59:48 [kernel] [ 2494.165805] 2.6.26-rc1-00007-g91b3a7a #217
> > May 11 10:59:48 [kernel] [ 2494.165807] -------------------------------------------------------
> > May 11 10:59:48 [kernel] [ 2494.165809] less/7053 is trying to acquire lock:
> > May 11 10:59:48 [kernel] [ 2494.165812] (tasklist_lock){..??}, at: [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
> > May 11 10:59:48 [kernel] [ 2494.165821]
> > May 11 10:59:48 [kernel] [ 2494.165822] but task is already holding lock:
> > May 11 10:59:48 [kernel] [ 2494.165824] (&tty->ctrl_lock){....}, at: [<ffffffff803d5f31>] tty_check_change+0x61/0x110
> > May 11 10:59:48 [kernel] [ 2494.165831]
> > May 11 10:59:48 [kernel] [ 2494.165832] which lock already depends on the new lock.
> > May 11 10:59:48 [kernel] [ 2494.165833]
> > May 11 10:59:48 [kernel] [ 2494.165835]
> > May 11 10:59:48 [kernel] [ 2494.165836] the existing dependency chain (in reverse order) is:
> > May 11 10:59:48 [kernel] [ 2494.165838]
> > May 11 10:59:48 [kernel] [ 2494.165839] -> #2 (&tty->ctrl_lock){....}:
> > May 11 10:59:48 [kernel] [ 2494.165843] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
> > May 11 10:59:48 [kernel] [ 2494.165851] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> > May 11 10:59:48 [kernel] [ 2494.165858] [<ffffffff804deee0>] _spin_lock_irqsave+0x40/0x60
> > May 11 10:59:48 [kernel] [ 2494.165866] [<ffffffff803d31b5>] __proc_set_tty+0x35/0xe0
> > May 11 10:59:48 [kernel] [ 2494.165873] [<ffffffff803d76d4>] tty_ioctl+0xbf4/0xfe0
> > May 11 10:59:48 [kernel] [ 2494.165880] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
> > May 11 10:59:48 [kernel] [ 2494.165888] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
> > May 11 10:59:48 [kernel] [ 2494.165895] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
> > May 11 10:59:48 [kernel] [ 2494.165902] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
> > May 11 10:59:48 [kernel] [ 2494.165910] [<ffffffffffffffff>] 0xffffffffffffffff
> > May 11 10:59:48 [kernel] [ 2494.165924]
> > May 11 10:59:48 [kernel] [ 2494.165925] -> #1 (&sighand->siglock){++..}:
> > May 11 10:59:48 [kernel] [ 2494.165929] [<ffffffff80253796>] __lock_acquire+0xf86/0x1080
> > May 11 10:59:48 [kernel] [ 2494.165936] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> > May 11 10:59:48 [kernel] [ 2494.165943] [<ffffffff804dec1f>] _spin_lock+0x2f/0x40
> > May 11 10:59:48 [kernel] [ 2494.165951] [<ffffffff8022d5a3>] copy_process+0x973/0x1210
> > May 11 10:59:48 [kernel] [ 2494.165959] [<ffffffff8022df12>] do_fork+0x82/0x2f0
> > May 11 10:59:48 [kernel] [ 2494.165967] [<ffffffff8020bfe1>] kernel_thread+0x81/0xde
> > May 11 10:59:48 [kernel] [ 2494.165974] [<ffffffff8020c048>] child_rip+0xa/0x12
> > May 11 10:59:48 [kernel] [ 2494.165981] [<ffffffffffffffff>] 0xffffffffffffffff
> > May 11 10:59:48 [kernel] [ 2494.166038]
> > May 11 10:59:48 [kernel] [ 2494.166039] -> #0 (tasklist_lock){..??}:
> > May 11 10:59:48 [kernel] [ 2494.166043] [<ffffffff802535ab>] __lock_acquire+0xd9b/0x1080
> > May 11 10:59:48 [kernel] [ 2494.166050] [<ffffffff80253922>] lock_acquire+0x92/0xc0
> > May 11 10:59:48 [kernel] [ 2494.166057] [<ffffffff804dede2>] _read_lock+0x32/0x50
> > May 11 10:59:48 [kernel] [ 2494.166063] [<ffffffff80232e95>] is_current_pgrp_orphaned+0x15/0x50
> > May 11 10:59:48 [kernel] [ 2494.166071] [<ffffffff803d5f80>] tty_check_change+0xb0/0x110
> > May 11 10:59:48 [kernel] [ 2494.166078] [<ffffffff803dac5f>] set_termios+0x1f/0x4c0
> > May 11 10:59:48 [kernel] [ 2494.166085] [<ffffffff803db379>] tty_mode_ioctl+0x279/0x3e0
> > May 11 10:59:48 [kernel] [ 2494.166092] [<ffffffff803db51d>] n_tty_ioctl+0x3d/0x260
> > May 11 10:59:48 [kernel] [ 2494.166100] [<ffffffff803d6c34>] tty_ioctl+0x154/0xfe0
> > May 11 10:59:48 [kernel] [ 2494.166107] [<ffffffff802a05e1>] vfs_ioctl+0x31/0x90
> > May 11 10:59:48 [kernel] [ 2494.166114] [<ffffffff802a06b3>] do_vfs_ioctl+0x73/0x2d0
> > May 11 10:59:48 [kernel] [ 2494.166121] [<ffffffff802a095a>] sys_ioctl+0x4a/0x80
> > May 11 10:59:48 [kernel] [ 2494.166128] [<ffffffff8020b5ab>] system_call_after_swapgs+0x7b/0x80
> > May 11 10:59:48 [kernel] [ 2494.166135] [<ffffffffffffffff>] 0xffffffffffffffff
Confused. I don't understand why do lockdep reports tasklist_lock vs ctrl_lock
conflict. What we seem to have is the problem with ->ctrl_lock vs ->siglock.
tty_check_change()->kill_pgrp() takes ->siglock under ->ctrl_lock, while
usually we take them in reverse order, proc_set_tty() for example.
The patch looks correct anyway, but perhaps tty_check_change() doesn't need
->ctrl_lock at all? We don't dereference tty->pgrp.
Oleg.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] tty_check_change-avoid-taking-tasklist_lock-while-holding-tty-ctrl_lock-simplify
2008-05-14 15:39 ` Oleg Nesterov
@ 2008-05-15 16:27 ` Oleg Nesterov
0 siblings, 0 replies; 4+ messages in thread
From: Oleg Nesterov @ 2008-05-15 16:27 UTC (permalink / raw)
To: Andrew Morton
Cc: Marcin Slusarz, LKML, Alan Cox, Alexander Viro, Peter Zijlstra
On 05/14, Oleg Nesterov wrote:
>
> The patch looks correct anyway, but perhaps tty_check_change() doesn't need
> ->ctrl_lock at all? We don't dereference tty->pgrp.
IOW, I think the patch below makes sense.
With the previous patch tty->ctrl_lock buys nothing, it only protects the
"task_pgrp(current) == tty->pgrp" check, but tty->pgrp can be changed right
after spin_unlock_irqrestore(tty->ctrl_lock) anyway.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
--- HL/drivers/char/tty_io.c~TTY 2008-05-15 19:09:35.000000000 +0400
+++ HL/drivers/char/tty_io.c 2008-05-15 19:11:57.000000000 +0400
@@ -1199,27 +1199,21 @@ EXPORT_SYMBOL_GPL(tty_find_polling_drive
* If we try to write to, or set the state of, a terminal and we're
* not in the foreground, send a SIGTTOU. If the signal is blocked or
* ignored, go ahead and perform the operation. (POSIX 7.2)
- *
- * Locking: ctrl_lock
*/
int tty_check_change(struct tty_struct *tty)
{
- unsigned long flags;
int ret = 0;
if (current->signal->tty != tty)
return 0;
- spin_lock_irqsave(&tty->ctrl_lock, flags);
-
if (!tty->pgrp) {
printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
- goto out_unlock;
+ goto out;
}
if (task_pgrp(current) == tty->pgrp)
- goto out_unlock;
- spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+ goto out;
if (is_ignored(SIGTTOU))
goto out;
if (is_current_pgrp_orphaned()) {
@@ -1231,9 +1225,6 @@ int tty_check_change(struct tty_struct *
ret = -ERESTARTSYS;
out:
return ret;
-out_unlock:
- spin_unlock_irqrestore(&tty->ctrl_lock, flags);
- return ret;
}
EXPORT_SYMBOL(tty_check_change);
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-05-15 16:26 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2008-05-12 18:32 [vfs/tty] possible circular locking dependency detected Marcin Slusarz
2008-05-14 1:47 ` Andrew Morton
2008-05-14 15:39 ` Oleg Nesterov
2008-05-15 16:27 ` [PATCH] tty_check_change-avoid-taking-tasklist_lock-while-holding-tty-ctrl_lock-simplify Oleg Nesterov
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