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    SubjectRe: [PATCH stable-rc queue/4.9 1/1] futex: Provide distinct return value when owner is exiting
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    On 2021/2/22 18:16, Greg KH wrote:
    > On Mon, Feb 22, 2021 at 03:03:28PM +0800, Xiaoming Ni wrote:
    >> From: Thomas Gleixner<tglx@linutronix.de>
    >>
    >> commit ac31c7ff8624409ba3c4901df9237a616c187a5d upstream.
    > This commit is already in the 4.9 tree. If the backport was incorrect,
    > say that here, and describe what went wrong and why this commit fixes
    > it.
    >
    > Also state what commit this fixes as well, otherwise this changelog just
    > looks like it is being applied again to the tree, which doesn't make
    > much sense.
    >
    > thanks,
    >
    > greg k-h
    > .

    I wrote a cover for it. but forgot to adjust the title of the cover:

    https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@huawei.com/


    I found a dead code in the queue/4.9 branch of the stable-rc repository.

    2021-02-03:
    commit c27f392040e2f6 ("futex: Provide distinct return value when
    owner is exiting")
    The function handle_exit_race does not exist. Therefore, the
    change in handle_exit_race() is ignored in the patch round.

    2021-02-22:
    commit e55cb811e612 ("futex: Cure exit race")
    Define the handle_exit_race() function,
    but no branch in the function returns EBUSY.
    As a result, dead code occurs in the attach_to_pi_owner():

    int ret = handle_exit_race(uaddr, uval, p);
    ...
    if (ret == -EBUSY)
    *exiting = p; /* dead code */

    To fix the dead code, modify the commit e55cb811e612 ("futex: Cure exit
    race"),
    or install a patch to incorporate the changes in handle_exit_race().

    I am unfamiliar with the processing of the stable-rc queue branch,
    and I cannot find the patch mail of the current branch in
    https://lore.kernel.org/lkml/?q=%22futex%3A+Cure+exit+race%22
    Therefore, I re-integrated commit ac31c7ff8624 ("futex: Provide distinct
    return value when owner is exiting").
    And wrote a cover (but forgot to adjust the title of the cover):

    https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@huawei.com/

    Thanks
    Xiaoming Ni


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