Messages in this thread | | | Date | Wed, 13 Nov 2019 10:04:14 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: Help requested: futex(..., FUTEX_WAIT_PRIVATE, ...) returns EPERM |
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On Tue, 12 Nov 2019, Harris, Robert wrote:
> I am investigating an issue on 4.9.184 in which futex() returns EPERM > intermittently for > > futex(uaddr, FUTEX_WAIT_PRIVATE, val, &timeout, NULL, 0) > > The failure affects an application in an AWS lambda; traditional > debugging approaches vary from difficult to impossible. I cannot > reproduce the problem at will, instrument the kernel, install a new > kernel or get an application core dump. > > Understanding the circumstances under which EPERM can be returned for > FUTEX_WAIT_PRIVATE would be useful but it is not a documented failure > mode. I have spent some time looking through futex.c but have not > found anything yet. I would be grateful for a hint from someone more > knowledgeable.
sys_futex(FUTEX_WAIT_PRIVATE) does not return -EPERM. Only the PI variants do that.
Thanks,
tglx
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