[PATCH v2][malloc] Use relaxed atomics for malloc have_fastchunks

[Chris Metcalf]

On 10/17/2017 7:08 PM, Joseph Myers wrote:
> I think this breaks the build for tilepro.  You're using atomic 
> operations
> on a bool field, and tilepro only supports atomic operations on 4-byte
> objects and gives errors for other sizes.  Generic code should only use
> atomics on int-size / pointer-size objects unless it knows the particular
> architecture supports atomics of other sizes (e.g. through
> __HAVE_64B_ATOMICS).

To be fair, we could also synthesize subword atomics for tilepro with 
compare
and swap on the surrounding word, so it's not technically impossible to add
this support. And (as Wilco already demonstrated) it's trivial to fix the
caller to work around this problem.

However, it's also true that tilepro is no longer an actively-maintained 
platform;
the tilegx platform has pretty well supplanted it in practice. Perhaps 
it is time
to look at obsoleting tilepro so that its presence in the tree doesn't 
block
forward progress for other architectures.  I'm not aware of any existing 
tilepro
customers that are looking to use newer versions of glibc.
-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
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