linux-kernel - Re: timerfd incompatibility on mips

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Date:	Thu, 27 Jan 2011 16:53:39 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Alexander Gordeev <lasaine@....cs.msu.su>
cc:	uClibc <uclibc@...ibc.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: timerfd incompatibility on mips

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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