Correct robust mutex / PI futex kernel assumptions (bug 9894)

[David Miller]

From: "Joseph S. Myers" <joseph@codesourcery.com>
Date: Tue, 25 Mar 2014 12:19:12 +0000

> On Tue, 25 Mar 2014, David Miller wrote:
> 
>> > and futex_32.h just uses the asm-generic version, which just returns 
>> > -ENOSYS.  Are you saying that if glibc is built for 32-bit plus V9/V8plus, 
>> > then the kernel that glibc binary runs under must have been built with 
>> > defined(__sparc__) && defined(__arch64__) true?  If so, what is the 
>> > relevant cpp condition in userspace for "glibc can assume a kernel with 
>> > functional futex_atomic_cmpxchg_inatomic"?
>> 
>> A 32-bit binary compiled for v9 can only execute on 64-bit kernels.
> 
> Thanks for the explanation.  What's the right preprocessor conditional for 
> requiring a 64-bit kernel (to replace the "defined __arch64__" in my 
> patch)?

There isn't.  You really have to base it upon the config triplet, by
placing the header file in question under a sparc32/v9 subdirectory.

You could include atomic.h and do tests on __sparc32_atomic_do_lock like
lowlevellock.h does, but that's really ugly.