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Date: Tue, 20 Apr 2010 06:14:20 -0700 From: Greg KH <gregkh@...e.de> To: Lai Jiangshan <laijs@...fujitsu.com> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, WANG Cong <xiyou.wangcong@...il.com>, Tejun Heo <tj@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [BUG] sysfs: don't use allocated key for lockdep On Tue, Apr 20, 2010 at 11:50:07AM +0800, Lai Jiangshan wrote: > Reported-by: Lai Jiangshan <laijs@...fujitsu.com> > > The commit 6992f5334995af474c2b58d010d08bc597f0f2fe > does wrong thing that use allocated key for lockdep_map. > > Lockdep requires keys that are static: > > lockdep_init_map() { > ...... > /* > * Sanity check, the lock-class key must be persistent: > */ > if (!static_obj(key)) { > printk("BUG: key %p not in .data!\n", key); > DEBUG_LOCKS_WARN_ON(1); > return; > } > lock->key = key; > ...... > } > > Could you please fix it. All in-kernel attributes should now be fixed, so what exactly is the remaining issue? > ---------------- > One other comment (not relate to this bug, but relate to the commit): > It is not a very good idea that use one lockdep class per sysfs attribute. > > First: we don't have too much lockdep class resource. > Second: lockdep validator is O(N*N) algorithm. > (N is the number of used lockdep class) > > So it is recommended that use only one class for a group of locks. > > For some nesting requirement, you can use > lock_acquire(...,subclass,...nest_lock,...) > > Or change the design. > -------------------- > > BUG: key ffff880042c68220 not in .data! > ------------[ cut here ]------------ > WARNING: at kernel/lockdep.c:2706 lockdep_init_map+0xe6/0x4fb() > Hardware name: Lenovo WQ T168/T468 G6 > Modules linked in: mptsas(+) mptscsih mptbase scsi_transport_sas ext4 jbd2 crc16 uhci_hcd ohci_hcd ehci_hcd > Pid: 1329, comm: modprobe Not tainted 2.6.34-rc3-22949-gbc8a97a-dirty #1 Please try 2.6.34-rc5 and let us know if this still shows up. thanks, greg k-h -- 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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