On Tue, Apr 13, 2010 at 08:38:43PM +0530, Balbir Singh wrote: > * Vivek Goyal <vgoyal@xxxxxxxxxx> [2010-04-13 10:03:02]: > > > On Tue, Apr 13, 2010 at 09:57:18AM -0400, Vivek Goyal wrote: > > > On Tue, Apr 13, 2010 at 01:45:53PM +0900, KAMEZAWA Hiroyuki wrote: > > > > > > > Typed wrong email id last time and mail bounced. So here is another > > attempt. > > > > > [..] > > > > -2. Locking > > > > +2.6 Locking > > > > > > > > -The memory controller uses the following hierarchy > > > > + lock_page_cgroup()/unlock_page_cgroup() should not be called under > > > > + mapping->tree_lock. > > > > > > > > > > Because I never understood very well, I will ask. Why lock_page_cgroup() > > > should not be called under mapping->tree_lock? > > > > > The closest reference I can find to a conversation regarding this is > > http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-05/msg05158.html > Thanks Balbir. So basically idea is that page_cgroup_lock() does not disable interrupts hence can be interrupted. So don't do lock_page_cgroup() in interrupt context at all otherwise it can lead to various kind of deadlock scenarios. One of those scenarios is lock_page_cgroup() under mapping->tree_lock. That helps. Thanks Vivek > -- > Three Cheers, > Balbir -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>