Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 8 Sep 2003 18:33:04 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] Re: today's futex changes |
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On Mon, 8 Sep 2003, Rusty Russell wrote: > OK, I've updated my patch on top of this. Mainly cosmetic, please > review. > > Name: Minor Tweaks To Jamie Lokier's Futex Patch > Author: Rusty Russell > Status: Booted on 2.6.0-test4-bk9 > Depends: Misc/futex-hugh.patch.gz > > D: Minor changes to Jamie's excellent futex patch. > D: 1) Remove obsolete comment above hash array decl. > D: 2) Semantics of futex on read-only pages unclear: require write perm. > D: 3) Clarify comment about TASK_INTERRUPTIBLE. > D: 4) Andrew Morton says spurious wakeup is a bug. Catch it. > D: 5) Use Jenkins hash.
Most of it (the futex_wait tweaks) looked fine to me - though I look forward to the first report of that BUG().
Part 2, requiring VM_WRITE and removing the comment on VM_MAYSHARE, seems a regression to me. Perhaps I misinterpreted Linus' action in taking Jamie's patch: I took that to mean he relented a little on his hardline position about VM_SHARED, and now accepts that in this context VM_MAYSHARE is more appropriate (easier to document). I know I argued that readonly futices are pointless, but I thought Jamie gave a good picture of how a readonly view could still be used. I'd rather that part were a separate patch, so Linus can merge or not as he wishes.
In part 5, the Jenkins hashing, I was puzzled by the "/4" in + (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
both.ptr would be a multiple of 32 (? seems to be that way on PIII and P4, though I gave up trying to work out quite how slab.c aligns), and both.word would be a multiple of 1 in the shared.pgoff case, or a multiple of PAGE_SIZE in the private.uaddr case (private.uaddr = uaddr >> PAGE_SHIFT might make more sense). Whereas both.offset would be a multiple of 4. I don't suppose Mr Jenkins will mind, but I did find the "/4" puzzling in that context.
Hugh
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