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    SubjectRe: [PATCHv3 6/6] tty/ldsem: Decrement wait_readers on timeouted down_read()
    On Tue, Sep 11, 2018 at 02:48:21AM +0100, Dmitry Safonov wrote:
    > It seems like when ldsem_down_read() fails with timeout, it misses
    > update for sem->wait_readers. By that reason, when writer finally
    > releases write end of the semaphore __ldsem_wake_readers() does adjust
    > sem->count with wrong value:
    > sem->wait_readers * (LDSEM_ACTIVE_BIAS - LDSEM_WAIT_BIAS)
    >
    > I.e, if update comes with 1 missed wait_readers decrement, sem->count
    > will be 0x100000001 which means that there is active reader and it'll
    > make any further writer to fail in acquiring the semaphore.
    >
    > It looks like, this is a dead-code, because ldsem_down_read() is never
    > called with timeout different than MAX_SCHEDULE_TIMEOUT, so it might be
    > worth to delete timeout parameter and error path fall-back..

    You might want to think about ditching that ldsem thing entirely, and
    use a regular rwsem ?

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