Messages in this thread | | | Date | Mon, 02 Jun 2014 10:41:16 -0400 | From | Peter Hurley <> | Subject | Re: tty/vt: Lockdep splat when Magic Sysrq SAK invoked |
| |
Hi Calvin,
On 06/21/2013 06:37 PM, Calvin Owens wrote: > Hello all, > > I get the following lockdep splat when I invoke the "ALT+SYSRQ+K" > combination on the keyboard. It usually happens the first time, but > doing it repeatedly always triggers it.
I know this is a year old but I believe this is fixed.
Could you confirm that you no longer can reproduce a lockdep report invoking SAK on 3.12+?
Regards, Peter Hurley
> [ 175.523980] SysRq : SAK > [ 175.524066] SAK: killed process 1629 (agetty): task_session(p)==tty->session > [ 178.213640] SysRq : SAK > [ 178.213745] SAK: killed process 1648 (agetty): task_session(p)==tty->session > [ 179.154891] SysRq : SAK > [ 179.154981] SAK: killed process 1649 (agetty): task_session(p)==tty->session > [ 180.409357] SysRq : SAK > [ 180.409429] SAK: killed process 1650 (agetty): task_session(p)==tty->session > [ 181.102312] SysRq : SAK > [ 181.102400] SAK: killed process 1651 (agetty): task_session(p)==tty->session > [ 181.866974] SysRq : SAK > [ 181.867057] SAK: killed process 1652 (agetty): task_session(p)==tty->session > [ 182.929591] SysRq : SAK > [ 182.929665] SAK: killed process 1653 (agetty): task_session(p)==tty->session > [ 184.221174] ====================================================== > [ 184.221174] [ INFO: possible circular locking dependency detected ] > [ 184.221175] 3.10.0-rc6-newinteloldnohz-00136-gf71194a #3 Not tainted > [ 184.221176] ------------------------------------------------------- > [ 184.221177] kworker/0:1/78 is trying to acquire lock: > [ 184.221182] (console_lock){+.+.+.}, at: [<ffffffff812f25a0>] do_con_write.part.25+0x40/0x1ed0 > [ 184.221182] > but task is already holding lock: > [ 184.221185] (&ldata->echo_lock){+.+...}, at: [<ffffffff812dd422>] process_echoes+0x62/0x310 > [ 184.221185] > which lock already depends on the new lock. > > [ 184.221186] > the existing dependency chain (in reverse order) is: > [ 184.221187] > -> #1 (&ldata->echo_lock){+.+...}: > [ 184.221190] [<ffffffff81095987>] lock_acquire+0x57/0x70 > [ 184.221193] [<ffffffff816bbaa2>] mutex_lock_nested+0x62/0x400 > [ 184.221194] [<ffffffff812deb73>] reset_buffer_flags+0x53/0x120 > [ 184.221195] [<ffffffff812dec58>] n_tty_flush_buffer+0x18/0x40 > [ 184.221197] [<ffffffff812e2a91>] tty_ldisc_flush+0x31/0x50 > [ 184.221198] [<ffffffff812da047>] __do_SAK+0x27/0x2b0 > [ 184.221199] [<ffffffff812e7feb>] vc_SAK+0x2b/0x40 > [ 184.221201] [<ffffffff8105fa4a>] process_one_work+0x1ca/0x480 > [ 184.221203] [<ffffffff8106015b>] worker_thread+0x11b/0x370 > [ 184.221204] [<ffffffff810682f6>] kthread+0xd6/0xe0 > [ 184.221205] [<ffffffff816c0a6c>] ret_from_fork+0x7c/0xb0 > [ 184.221206] > -> #0 (console_lock){+.+.+.}: > [ 184.221208] [<ffffffff810951d8>] __lock_acquire+0x1ae8/0x1d50 > [ 184.221209] [<ffffffff81095987>] lock_acquire+0x57/0x70 > [ 184.221211] [<ffffffff810432af>] console_lock+0x6f/0x80 > [ 184.221212] [<ffffffff812f25a0>] do_con_write.part.25+0x40/0x1ed0 > [ 184.221213] [<ffffffff812f4464>] con_put_char+0x34/0x40 > [ 184.221214] [<ffffffff812da7bf>] tty_put_char+0x1f/0x40 > [ 184.221215] [<ffffffff812dd1bd>] do_output_char+0x7d/0x210 > [ 184.221217] [<ffffffff812dd537>] process_echoes+0x177/0x310 > [ 184.221218] [<ffffffff812dfac2>] n_tty_receive_buf+0xa12/0x1570 > [ 184.221219] [<ffffffff812e3716>] flush_to_ldisc+0x116/0x160 > [ 184.221220] [<ffffffff8105fa4a>] process_one_work+0x1ca/0x480 > [ 184.221221] [<ffffffff8106015b>] worker_thread+0x11b/0x370 > [ 184.221222] [<ffffffff810682f6>] kthread+0xd6/0xe0 > [ 184.221223] [<ffffffff816c0a6c>] ret_from_fork+0x7c/0xb0 > [ 184.221223] > other info that might help us debug this: > > [ 184.221223] Possible unsafe locking scenario: > > [ 184.221224] CPU0 CPU1 > [ 184.221224] ---- ---- > [ 184.221224] lock(&ldata->echo_lock); > [ 184.221225] lock(console_lock); > [ 184.221226] lock(&ldata->echo_lock); > [ 184.221226] lock(console_lock); > [ 184.221226] > *** DEADLOCK *** > > [ 184.221227] 4 locks held by kworker/0:1/78: > [ 184.221229] #0: (events){.+.+.+}, at: [<ffffffff8105f9ed>] process_one_work+0x16d/0x480 > [ 184.221231] #1: ((&buf->work)){+.+...}, at: [<ffffffff8105f9ed>] process_one_work+0x16d/0x480 > [ 184.221233] #2: (&ldata->output_lock){+.+...}, at: [<ffffffff812dd40d>] process_echoes+0x4d/0x310 > [ 184.221234] #3: (&ldata->echo_lock){+.+...}, at: [<ffffffff812dd422>] process_echoes+0x62/0x310 > [ 184.221235] > stack backtrace: > [ 184.221236] CPU: 0 PID: 78 Comm: kworker/0:1 Not tainted 3.10.0-rc6-newinteloldnohz-00136-gf71194a #3 > [ 184.221237] Hardware name: ASUSTeK COMPUTER INC. K55A/K55A, BIOS K55A.404 08/20/2012 > [ 184.221238] Workqueue: events flush_to_ldisc > [ 184.221241] ffffffff8259f260 ffff8801199038c8 ffffffff816b77ab ffff880119903918 > [ 184.221242] ffffffff816b4dd7 0000000000000001 ffff8801199039a0 ffff88011a34e970 > [ 184.221243] ffff88011a34eff8 ffff88011a34e970 ffff88011a34f020 ffffffff8259f260 > [ 184.221244] Call Trace: > [ 184.221245] [<ffffffff816b77ab>] dump_stack+0x19/0x1b > [ 184.221248] [<ffffffff816b4dd7>] print_circular_bug+0x1fb/0x20c > [ 184.221249] [<ffffffff810951d8>] __lock_acquire+0x1ae8/0x1d50 > [ 184.221251] [<ffffffff81095987>] lock_acquire+0x57/0x70 > [ 184.221252] [<ffffffff812f25a0>] ? do_con_write.part.25+0x40/0x1ed0 > [ 184.221253] [<ffffffff810432af>] console_lock+0x6f/0x80 > [ 184.221254] [<ffffffff812f25a0>] ? do_con_write.part.25+0x40/0x1ed0 > [ 184.221255] [<ffffffff812f25a0>] do_con_write.part.25+0x40/0x1ed0 > [ 184.221257] [<ffffffff816bbd36>] ? mutex_lock_nested+0x2f6/0x400 > [ 184.221258] [<ffffffff8109216d>] ? trace_hardirqs_on_caller+0xfd/0x1c0 > [ 184.221259] [<ffffffff812f4464>] con_put_char+0x34/0x40 > [ 184.221261] [<ffffffff812da7bf>] tty_put_char+0x1f/0x40 > [ 184.221262] [<ffffffff812dd1bd>] do_output_char+0x7d/0x210 > [ 184.221263] [<ffffffff812dd537>] process_echoes+0x177/0x310 > [ 184.221265] [<ffffffff812dfac2>] n_tty_receive_buf+0xa12/0x1570 > [ 184.221266] [<ffffffff81091fb2>] ? mark_held_locks+0x72/0x130 > [ 184.221267] [<ffffffff816bf6f5>] ? _raw_spin_unlock_irqrestore+0x65/0x80 > [ 184.221269] [<ffffffff8109216d>] ? trace_hardirqs_on_caller+0xfd/0x1c0 > [ 184.221270] [<ffffffff812e3716>] flush_to_ldisc+0x116/0x160 > [ 184.221271] [<ffffffff8105fa4a>] process_one_work+0x1ca/0x480 > [ 184.221272] [<ffffffff8105f9ed>] ? process_one_work+0x16d/0x480 > [ 184.221273] [<ffffffff8106015b>] worker_thread+0x11b/0x370 > [ 184.221274] [<ffffffff81060040>] ? rescuer_thread+0x300/0x300 > [ 184.221275] [<ffffffff810682f6>] kthread+0xd6/0xe0 > [ 184.221276] [<ffffffff816bf73b>] ? _raw_spin_unlock_irq+0x2b/0x60 > [ 184.221277] [<ffffffff81068220>] ? __kthread_unpark+0x50/0x50 > [ 184.221278] [<ffffffff816c0a6c>] ret_from_fork+0x7c/0xb0 > [ 184.221279] [<ffffffff81068220>] ? __kthread_unpark+0x50/0x50
| |