timerfd incompatibility on mips

From: Alexander Gordeev
Date: Thu Jan 27 2011 - 19:25:05 EST


I've just found a problem with TFD_NONBLOCK flag that can be passed to

<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.


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