Messages in this thread | | | Date | Fri, 6 Jun 2014 16:07:32 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] Revert lockdep check in raw_seqcount_begin |
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On Thu, Jun 05, 2014 at 11:31:01AM -0400, Trond Myklebust wrote: > This commit reverts the addition of lockdep checking to raw_seqcount_begin > for the following reasons: > > 1) It violates the naming convention that raw_* functions should not > do lockdep checks (a convention that is also followed by the other > raw_*_seqcount_begin functions). > 2) raw_seqcount_begin does not spin, so it can only be part of an ABBA > deadlock in very special circumstances (for instance if a lock > is held across the entire raw_seqcount_begin()+read_seqcount_retry() > loop while also being taken inside the write_seqcount protected area). > 3) It is causing false positives with some existing callers, and there > is no non-lockdep alternative for those callers to use. > > None of the three existing callers (__d_lookup_rcu, netdev_get_name, and > the NFS state code) appear to use the function in a manner that is ABBA > deadlock prone. > > Fixes: 1ca7d67cf5d5: seqcount: Add lockdep functionality to seqcount/seqlock > Cc: John Stultz <john.stultz@linaro.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Link: http://lkml.kernel.org/r/CAHQdGtRR6SvEhXiqWo24hoUh9AU9cL82Z8Z-d8-7u951F_d+5g@mail.gmail.com > Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Thanks Trond!
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