Messages in this thread |  | | Date | Fri, 1 Nov 2013 11:15:14 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 1/4] mm/rmap: per anon_vma lock |
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On Fri, Nov 01, 2013 at 06:07:07PM +0800, Yuanhan Liu wrote: > > I also want to point out that lately we've seen several changes sent > > out that relax locking with no accompanying explanation of why the > > relaxed locking would be safe. Please don't do that - having a lot of > > performance data is worthless if you can't explain why the new locking > > is safe. > > Agreed. > > > And I'm not asking to prove a negative ('lack of any possible > > races') there, but at least in this case one could dig out why the > > root anon vma locking was introduced and if they think that this > > reason doesn't apply anymore, explain why... > > It was introduced by commit 2b575eb6(And, BTW, I'm sorry that this commit log > about bb4aa39676f is wrong) > > commit 2b575eb64f7a9c701fb4bfdb12388ac547f6c2b6 > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Tue May 24 17:12:11 2011 -0700 > > mm: convert anon_vma->lock to a mutex > > Straightforward conversion of anon_vma->lock to a mutex. > > As you can see, Peter didn't tell why before. Honestly speaking, that > was my originaly concern as well. I tried to find some possible races; > I guess I may miss something.
Bullshit; I didn't change the locking. I only changed the lock primitive from a spinlock to a mutex. The anon_vma->root->lock is completely unrelated to this change.
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