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Re: [Qemu-devel] [PATCH 10/23] userfaultfd: add new syscall to provide m
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From: |
Linus Torvalds |
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Subject: |
Re: [Qemu-devel] [PATCH 10/23] userfaultfd: add new syscall to provide memory externalization |
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Date: |
Fri, 15 May 2015 11:22:09 -0700 |
On Fri, May 15, 2015 at 9:04 AM, Andrea Arcangeli <address@hidden> wrote:
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> To fix it I added this along a comment:
Ok, this looks good as a explanation/fix for the races (and also as an
example of my worry about waitqueue_active() use in general).
However, it now makes me suspect that the optimistic "let's check if
they are even active" may not be worth it any more. You're adding a
"smp_mb()" in order to avoid taking the real lock. Although I guess
there are two locks there (one for each wait-queue) so maybe it's
worth it.
Linus
- [Qemu-devel] [PATCH 02/23] userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key, (continued)
- [Qemu-devel] [PATCH 02/23] userfaultfd: waitqueue: add nr wake parameter to __wake_up_locked_key, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 08/23] userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 07/23] userfaultfd: call handle_userfault() for userfaultfd_missing() faults, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 13/23] userfaultfd: change the read API to return a uffd_msg, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 23/23] userfaultfd: UFFDIO_COPY and UFFDIO_ZEROPAGE, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 01/23] userfaultfd: linux/Documentation/vm/userfaultfd.txt, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 16/23] userfaultfd: allocate the userfaultfd_ctx cacheline aligned, Andrea Arcangeli, 2015/05/14
- [Qemu-devel] [PATCH 10/23] userfaultfd: add new syscall to provide memory externalization, Andrea Arcangeli, 2015/05/14
- Re: [Qemu-devel] [PATCH 00/23] userfaultfd v4, Pavel Emelyanov, 2015/05/18
- Re: [Qemu-devel] [PATCH 00/23] userfaultfd v4, Andrew Morton, 2015/05/19
- Re: [Qemu-devel] [PATCH 00/23] userfaultfd v4, Kirill Smelkov, 2015/05/21