Re: timerfd incompatibility on mips

From: Davide Libenzi
Date: Thu Jan 27 2011 - 19:53:52 EST

On Fri, 28 Jan 2011, Alexander Gordeev wrote:

> Hi!
> I've just found a problem with TFD_NONBLOCK flag that can be passed to
> timerfd_create.
> <uclibc>/libc/sysdeps/linux/common/sys/timerfd.h which is installed
> to /usr/include/sys/timerfd.h defines TFD_NONBLOCK as 04000 ie 0x800.
> BTW glibc/eglibc headers do the same thing.
> <linux>/include/linux/timerfd.h declares it as O_NONBLOCK which is
> defined in fcntl.h. Usually O_NONBLOCK is 0x800 too but some
> architectures including MIPS it redefine it:
> arch/mips/include/asm/fcntl.h:#define O_NONBLOCK 0x0080
> arch/alpha/include/asm/fcntl.h:#define O_NONBLOCK 00004
> arch/sparc/include/asm/fcntl.h:#define O_NONBLOCK 0x4000
> arch/parisc/include/asm/fcntl.h:#define O_NONBLOCK 000200004
> My tests show that kernel thinks that TFD_NONBLOCK is 0x80 on MIPS. I
> get what I want when I pass 0x80 and EINVAL when I pass 0x800. I don't
> know why there are such uncertain things in Linux. Probably the problem
> should be fixed in the kernel.
> Right now one cannot use timerfd_create(..., TFD_NONBLOCK) on MIPS but
> can use timerfd_create(..., O_NONBLOCK) instead.

Ther kernel definition (include/linux/timerfd.h) maps it directly to
O_NONBLOCK, but I am noticing that glibc bolt in the value.
I don't think this is a kernel fix.

- Davide

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