Messages in this thread | | | From | Linus Torvalds <> | Date | Fri, 12 Nov 2010 15:52:55 -0800 | Subject | Re: [patches] seqlock: add barrier-less special cases for seqcounts |
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On Fri, Nov 12, 2010 at 3:06 PM, Nick Piggin <npiggin@kernel.dk> wrote: . ... > seq2 = read_seqlock_begin(&child->d_seq); > if (read_seqcount_retry(&dentry->d_seq, seq)) > /* bail out */
So the only issue is that this particular back-to-back sequence with these kinds of "take one seqlock and release the previous one" where you currently end up having basically one smp_rmb() at the end of "read_seqlock_begin()", only to be followed immediately by another one starting out the "read_seqcount_retry()"?
If so, I think we should make _that_ operation ("move from one seqlock to another") be the special one, because it smells like in general, using the special non-locking versions is going to be a very subtle interface.
Linus
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