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Message-ID: <513A9BCA.9020402@lwfinger.net>
Date: Fri, 08 Mar 2013 20:17:46 -0600
From: Larry Finger <Larry.Finger@...inger.net>
To: LKML <linux-kernel@...r.kernel.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Russell King <linux@....linux.org.uk>
Subject: [3.9-rc1] Locking dependency problem
In kernel 3.9-rc1, I get the following lockdep warning. This kernel is from the
wireless-testing tree, but I have seen the same message from the mainline kernel.
[ 4199.401157]
[ 4199.401159] ======================================================
[ 4199.401160] [ INFO: possible circular locking dependency detected ]
[ 4199.401163] 3.9.0-rc1-wl+ #124 Tainted: G W
[ 4199.401164] -------------------------------------------------------
[ 4199.401167] kworker/0:3/2382 is trying to acquire lock:
[ 4199.401177] (&fb_info->lock){+.+.+.}, at: [<ffffffff8124c371>]
lock_fb_info+0x21/0x60
[ 4199.401177]
[ 4199.401177] but task is already holding lock:
[ 4199.401183] (console_lock){+.+.+.}, at: [<ffffffff812c487e>]
console_callback+0xe/0x130
[ 4199.401184]
[ 4199.401184] which lock already depends on the new lock.
[ 4199.401184]
[ 4199.401185]
[ 4199.401185] the existing dependency chain (in reverse order) is:
[ 4199.401187]
[ 4199.401187] -> #1 (console_lock){+.+.+.}:
[ 4199.401193] [<ffffffff810a49c8>] lock_acquire+0xa8/0x1f0
[ 4199.401197] [<ffffffff81041a87>] console_lock+0x77/0x80
[ 4199.401200] [<ffffffff8124e0a2>] register_framebuffer+0x1b2/0x300
[ 4199.401205] [<ffffffff818c0d9d>] vesafb_probe+0x6ec/0x76c
[ 4199.401208] [<ffffffff812e429e>] platform_drv_probe+0x3e/0x70
[ 4199.401211] [<ffffffff812e2215>] driver_probe_device+0x75/0x230
[ 4199.401213] [<ffffffff812e2473>] __driver_attach+0xa3/0xb0
[ 4199.401216] [<ffffffff812e0485>] bus_for_each_dev+0x55/0x90
[ 4199.401218] [<ffffffff812e1d69>] driver_attach+0x19/0x20
[ 4199.401220] [<ffffffff812e1899>] bus_add_driver+0x109/0x270
[ 4199.401223] [<ffffffff812e2b22>] driver_register+0x72/0x170
[ 4199.401226] [<ffffffff812e3b11>] platform_driver_register+0x41/0x50
[ 4199.401228] [<ffffffff812e3b36>] platform_driver_probe+0x16/0xa0
[ 4199.401231] [<ffffffff818c066e>] vesafb_init+0x215/0x258
[ 4199.401235] [<ffffffff81000302>] do_one_initcall+0x122/0x180
[ 4199.401239] [<ffffffff8189af4e>] kernel_init_freeable+0x103/0x192
[ 4199.401242] [<ffffffff814544e9>] kernel_init+0x9/0xf0
[ 4199.401247] [<ffffffff8146cfbc>] ret_from_fork+0x7c/0xb0
[ 4199.401250]
[ 4199.401250] -> #0 (&fb_info->lock){+.+.+.}:
[ 4199.401252] [<ffffffff810a3b89>] __lock_acquire+0x1479/0x1c70
[ 4199.401255] [<ffffffff810a49c8>] lock_acquire+0xa8/0x1f0
[ 4199.401257] [<ffffffff81469189>] mutex_lock_nested+0x69/0x370
[ 4199.401259] [<ffffffff8124c371>] lock_fb_info+0x21/0x60
[ 4199.401263] [<ffffffff812598db>] fbcon_blank+0x29b/0x2e0
[ 4199.401266] [<ffffffff812c1706>] do_blank_screen+0x1d6/0x280
[ 4199.401269] [<ffffffff812c48cf>] console_callback+0x5f/0x130
[ 4199.401273] [<ffffffff81064761>] process_one_work+0x1f1/0x660
[ 4199.401275] [<ffffffff81064f70>] worker_thread+0x110/0x380
[ 4199.401279] [<ffffffff8106a756>] kthread+0xd6/0xe0
[ 4199.401282] [<ffffffff8146cfbc>] ret_from_fork+0x7c/0xb0
[ 4199.401282]
[ 4199.401282] other info that might help us debug this:
[ 4199.401282]
[ 4199.401283] Possible unsafe locking scenario:
[ 4199.401283]
[ 4199.401284] CPU0 CPU1
[ 4199.401284] ---- ----
[ 4199.401286] lock(console_lock);
[ 4199.401287] lock(&fb_info->lock);
[ 4199.401288] lock(console_lock);
[ 4199.401290] lock(&fb_info->lock);
[ 4199.401290]
[ 4199.401290] *** DEADLOCK ***
[ 4199.401290]
[ 4199.401292] 3 locks held by kworker/0:3/2382:
[ 4199.401297] #0: (events){.+.+.+}, at: [<ffffffff810646f5>]
process_one_work+0x185/0x660
[ 4199.401301] #1: (console_work){+.+...}, at: [<ffffffff810646f5>]
process_one_work+0x185/0x660
[ 4199.401305] #2: (console_lock){+.+.+.}, at: [<ffffffff812c487e>]
console_callback+0xe/0x130
[ 4199.401306]
[ 4199.401306] stack backtrace:
[ 4199.401308] Pid: 2382, comm: kworker/0:3 Tainted: G W 3.9.0-rc1-wl+
#124
[ 4199.401309] Call Trace:
[ 4199.401312] [<ffffffff81464497>] print_circular_bug+0x28e/0x29f
[ 4199.401315] [<ffffffff8146c7f3>] ? retint_restore_args+0x13/0x13
[ 4199.401318] [<ffffffff810a3b89>] __lock_acquire+0x1479/0x1c70
[ 4199.401322] [<ffffffff812628db>] ? bitfill_aligned+0x8b/0x140
[ 4199.401324] [<ffffffff810a49c8>] lock_acquire+0xa8/0x1f0
[ 4199.401326] [<ffffffff8124c371>] ? lock_fb_info+0x21/0x60
[ 4199.401329] [<ffffffff81469189>] mutex_lock_nested+0x69/0x370
[ 4199.401331] [<ffffffff8124c371>] ? lock_fb_info+0x21/0x60
[ 4199.401333] [<ffffffff8125ca3c>] ? bit_clear+0xcc/0x100
[ 4199.401336] [<ffffffff8125620e>] ? fbcon_clear+0x1be/0x1f0
[ 4199.401338] [<ffffffff8124c371>] lock_fb_info+0x21/0x60
[ 4199.401341] [<ffffffff812598db>] fbcon_blank+0x29b/0x2e0
[ 4199.401343] [<ffffffff8146c17a>] ? _raw_spin_unlock_irqrestore+0x3a/0x80
[ 4199.401346] [<ffffffff810a54ed>] ? trace_hardirqs_on_caller+0x10d/0x1a0
[ 4199.401349] [<ffffffff810a558d>] ? trace_hardirqs_on+0xd/0x10
[ 4199.401354] [<ffffffff8105303a>] ? try_to_del_timer_sync+0x4a/0x60
[ 4199.401356] [<ffffffff8105310a>] ? del_timer_sync+0xba/0xf0
[ 4199.401359] [<ffffffff81053050>] ? try_to_del_timer_sync+0x60/0x60
[ 4199.401362] [<ffffffff812c1706>] do_blank_screen+0x1d6/0x280
[ 4199.401364] [<ffffffff812c48cf>] console_callback+0x5f/0x130
[ 4199.401367] [<ffffffff81064761>] process_one_work+0x1f1/0x660
[ 4199.401370] [<ffffffff810646f5>] ? process_one_work+0x185/0x660
[ 4199.401372] [<ffffffff81064f70>] worker_thread+0x110/0x380
[ 4199.401375] [<ffffffff810a558d>] ? trace_hardirqs_on+0xd/0x10
[ 4199.401377] [<ffffffff81064e60>] ? rescuer_thread+0x250/0x250
[ 4199.401379] [<ffffffff8106a756>] kthread+0xd6/0xe0
[ 4199.401382] [<ffffffff8146c1eb>] ? _raw_spin_unlock_irq+0x2b/0x50
[ 4199.401385] [<ffffffff8106a680>] ? __init_kthread_worker+0x70/0x70
[ 4199.401388] [<ffffffff8146cfbc>] ret_from_fork+0x7c/0xb0
[ 4199.401390] [<ffffffff8106a680>] ? __init_kthread_worker+0x70/0x70
This problem seems to be related to
http://www.mentby.com/russell-king-2/bug-circular-locking-dependency-detected.html.
Losing lockdep when the screen blanks is certainly a hindrance when trying to
debug new drivers.
Thanks,
Larry
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