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Date: Wed, 10 Mar 2010 01:05:35 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Jens Axboe <jens.axboe@oracle.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, Greg KH <gregkh@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Steven Rostedt <rostedt@goodmis.org>, Paul Mackerras <paulus@samba.org>,
       Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>,
       Li Zefan <lizf@cn.fujitsu.com>, Lai Jiangshan <laijs@cn.fujitsu.com>,
       Masami Hiramatsu <mhiramat@redhat.com>
Subject: Re: [PATCH 1/3] lockdep: Move lock events under lockdep recursion
	protection
Message-ID: <20100310000533.GF5058@nowhere>
References: <1267599302-2886-1-git-send-regression-fweisbec@gmail.com> <1267599302-2886-2-git-send-regression-fweisbec@gmail.com> <20100309083410.GD5768@kernel.dk> <20100309083536.GE5768@kernel.dk>
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On Tue, Mar 09, 2010 at 09:35:37AM +0100, Jens Axboe wrote:
> Which, btw, throws a new lockdep warning fest:
> 
> [   42.247718] scsi7 : ioc0: LSISAS1068E B3, FwRev=011b0300h, Ports=1, MaxQ=483, IRQ=26
> [   42.281125] BUG: key ffff880c7cb75250 not in .data!
> [   42.288346] ------------[ cut here ]------------
> [   42.294490] WARNING: at kernel/lockdep.c:2706 lockdep_init_map+0x545/0x5f0()
> [   42.304013] Hardware name: QSSC-S4R
> [   42.309674] Modules linked in: hid_apple usbhid ehci_hcd uhci_hcd usbcore nls_base mptsas(+) mptscsih mptbase scsi_transport_sas igb sg sr_mod cdrom
> [   42.332072] Pid: 5197, comm: modprobe Not tainted 2.6.34-rc1 #176
> [   42.340597] Call Trace:
> [   42.345335]  [<ffffffff8107fb8d>] ? is_module_address+0x2d/0x60
> [   42.353670]  [<ffffffff81074aa5>] ? lockdep_init_map+0x545/0x5f0
> [   42.362154]  [<ffffffff81044648>] warn_slowpath_common+0x78/0xd0
> [   42.371913]  [<ffffffff810446af>] warn_slowpath_null+0xf/0x20
> [   42.380109]  [<ffffffff81074aa5>] lockdep_init_map+0x545/0x5f0



This doesn't look related to my patch, it also happen in -rc1 right?



> [   42.388402]  [<ffffffff81156636>] ? sysfs_new_dirent+0x76/0x120


This calls:

#define sysfs_dirent_init_lockdep(sd)				\
do {								\
	struct attribute *attr = sd->s_attr.attr;		\
	struct lock_class_key *key = attr->key;			\
	if (!key)						\
		key = &attr->skey;				\
								\
	lockdep_init_map(&sd->dep_map, "s_active", key, 0);	\
} while(0)


Looks like the struct lock_class_key is dynamically allocated
and lockdep doesn't like that.