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    SubjectRe: Dead circle in epoll file descriptor causes soft lockup on kernel 3.2.12
    On Tue, Mar 27, 2012 at 10:05:10AM -0400, Jason Baron wrote:
    > On Tue, Mar 27, 2012 at 11:51:16AM +0400, Yurij M. Plotnikov wrote:
    > > Adding epoll file descriptors in each other in circle causes soft
    > > lockup on kernel 3.2.12 (I'm using Debian kernel
    > > 3.2.0-0.bpo.1-amd64). The following steps describe the problem:
    > >
    > > 1. epoll_create(1) -> 3
    > > 2. epoll_create(1) -> 4
    > > 3. socket(SOCK_STREAM) -> 5
    > > 4. bind(5, 0.0.0.0:0) -> 0
    > > 5. listen(5, 1) -> 0
    > > 6. epoll_ctl(3, ADD, 5, events = 0) -> 0
    > > 7. epoll_ctl(3, ADD, 4, events = EPOLLIN) -> 0
    > > 8. epoll_ctl(4, ADD, 3, events = EPOLLIN) -> -1(ELOOP)
    > > 9. close(3) -> 0
    > > 10. close(4) -> 0
    > > 11. close(5) -> 0
    > >
    > > After repetaing this sequence 2-3 times soft lockup appers. In
    > > attachment c program to reproduce this problem.
    > >
    >
    > Good catch. The patch below should fix this - please verify. Thanks.

    Verified. You patch solves our problem. Thank you very much for fast
    response.

    --
    Alexandra N. Kossovsky
    OKTET Labs (http://www.oktetlabs.ru/)


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