Messages in this thread | | | Date | Thu, 14 May 2009 07:18:01 +0530 | From | Balbir Singh <> | Subject | Re: [BUGFIX][PATCH] memcg: fix deadlock between lock_page_cgroupand mapping tree_lock |
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* Andrew Morton <akpm@linux-foundation.org> [2009-05-13 11:56:26]:
> On Wed, 13 May 2009 13:30:31 +0900 > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > > mapping->tree_lock can be aquired from interrupt context. > > Then, following dead lock can occur. > > > > Assume "A" as a page. > > > > CPU0: > > lock_page_cgroup(A) > > interrupted > > -> take mapping->tree_lock. > > CPU1: > > take mapping->tree_lock > > -> lock_page_cgroup(A) > > And we didn't find out about this because lock_page_cgroup() uses > bit_spin_lock(), and lockdep doesn't handle bit_spin_lock(). > > It would perhaps be useful if one of you guys were to add a spinlock to > struct page, convert lock_page_cgroup() to use that spinlock then run a > full set of tests under lockdep, see if it can shake out any other bugs. >
May be under DEBUG_VM we could do that. Good suggestion!
-- Balbir
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