Re: epoll_wait returning EFAULT on Linux 3.2.78

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От Greg Stark
Тема Re: epoll_wait returning EFAULT on Linux 3.2.78
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Msg-id CAM-w4HMNG--h739AO61LjWY07qMenJJ-JCmUNmhNs4xBGcNpBg@mail.gmail.com
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Ответ на Re: epoll_wait returning EFAULT on Linux 3.2.78  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: epoll_wait returning EFAULT on Linux 3.2.78  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Thu, Jun 2, 2016 at 3:50 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> The man page for epoll_wait suggests that that implies a bad pointer
> value for the events array.  You're showing
>         epoll_ret_events = 0x9c0ad4
> which is not obviously bad, but it's also only 4-byte aligned.
> I notice that CreateWaitEventSet() is being remarkably cavalier
> about alignment requirements; maybe it ought to make some effort
> to ensure that epoll_ret_events is maxaligned.


That makes a certain amount of sense as This is Debian Sparc64 which
as I understand it has the kernel compiled in 64-bit mode but not most
of userland. I bet if I compile Postgres in 64-bit mode it'll turn up
as an alignment issue in userland before it even reaches the kernel.
Or maybe not, maybe it's just that __put_user is stricter about
alignment than really necessary.

-- 
greg



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