https://github.com/torvalds/linux
Revision dd34739c03f2f9a79403d33419c2e61e11b4c403 authored by Linus Torvalds on 18 June 2011, 02:05:36 UTC, committed by Linus Torvalds on 18 June 2011, 02:24:11 UTC
Hugh Dickins points out that lockdep (correctly) spots a potential deadlock on the anon_vma lock, because we now do a GFP_KERNEL allocation of anon_vma_chain while doing anon_vma_clone(). The problem is that page reclaim will want to take the anon_vma lock of any anonymous pages that it will try to reclaim. So re-organize the code in anon_vma_clone() slightly: first do just a GFP_NOWAIT allocation, which will usually work fine. But if that fails, let's just drop the lock and re-do the allocation, now with GFP_KERNEL. End result: not only do we avoid the locking problem, this also ends up getting better concurrency in case the allocation does need to block. Tim Chen reports that with all these anon_vma locking tweaks, we're now almost back up to the spinlock performance. Reported-and-tested-by: Hugh Dickins <hughd@google.com> Tested-by: Tim Chen <tim.c.chen@linux.intel.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andi Kleen <ak@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tip revision: dd34739c03f2f9a79403d33419c2e61e11b4c403 authored by Linus Torvalds on 18 June 2011, 02:05:36 UTC
mm: avoid anon_vma_chain allocation under anon_vma lock
mm: avoid anon_vma_chain allocation under anon_vma lock
Tip revision: dd34739
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