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Date: Mon, 16 Nov 2015 16:43:00 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: kernel test robot <ying.huang@...ux.intel.com> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>, lkp@...org, LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>, "K. Y. Srinivasan" <kys@...rosoft.com>, Seth Jennings <sjenning@...hat.com>, Xie XiuQi <xiexiuqi@...wei.com>, Prarit Bhargava <prarit@...hat.com>, Baoquan He <bhe@...hat.com>, Jiri Kosina <jkosina@...e.cz>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, HATAYAMA Daisuke <d.hatayama@...fujitsu.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [lkp] [panic] [ BUG: bad unlock balance detected! ] On Mon, 16 Nov 2015 11:12:50 +0800 kernel test robot <ying.huang@...ux.intel.com> wrote: > FYI, we noticed the below changes on > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > commit 08d78658f393fefaa2e6507ea052c6f8ef4002a2 ("panic: release stale console lock to always get the logbuf printed out") > > ... > > [ 38.408623] ===================================== > [ 38.408623] [ BUG: bad unlock balance detected! ] > [ 38.408627] 4.3.0-08150-g08d7865 #1 Not tainted > [ 38.408627] ------------------------------------- > [ 38.408631] swapper/0/1 is trying to release lock (console_lock) at: > [ 38.408639] [<ffffffff811a3cb1>] panic+0x124/0x213 > [ 38.408640] but there are no more locks to release! > [ 38.408641] > [ 38.408641] other info that might help us debug this: > [ 38.408642] 2 locks held by swapper/0/1: > [ 38.408651] #0: (oom_lock){+.+...}, at: [<ffffffff811add45>] __alloc_pages_slowpath+0x5bd/0x68d > [ 38.408656] #1: (panic_lock){......}, at: [<ffffffff811a3bd9>] panic+0x4c/0x213 > [ 38.408657] > [ 38.408657] stack backtrace: > [ 38.408659] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.3.0-08150-g08d7865 #1 > [ 38.408660] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 > [ 38.408665] 0000000000000000 ffff8800132bba78 ffffffff8173760d ffff8800132b4040 > [ 38.408668] ffff8800132bbaa0 ffffffff8111328c 00000000ffffffff ffff8800132b4040 > [ 38.408670] ffffffff8406a080 ffff8800132bbb18 ffffffff8111626c ffffffff811139d1 > [ 38.408671] Call Trace: > [ 38.408678] [<ffffffff8173760d>] dump_stack+0x4b/0x63 > [ 38.408682] [<ffffffff8111328c>] print_unlock_imbalance_bug+0xc7/0xd0 Yup, we can't have this happen. Can we instead do this? if (is_console_locked()) console_unlock(); It's racy, but more accurate than what we have now? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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