Re: PI mutex support for pthread_cond_* now in nptl

[Torvald Riegel <triegel@redhat.com>]

On Tue, 2013-02-19 at 17:18 +0000, Joseph S. Myers wrote:
> On Tue, 19 Feb 2013, Richard Henderson wrote:
> 
> > Any chance we can move these macros into a generic linux header?
> > Given that we're using INTERNAL_SYSCALL macros, the definitions ought to be
> > the same for all targets.
> 
> Generally most of lowlevellock.h should probably be shared between 
> architectures.  (If some architectures don't implement a particular 
> feature as of a particular kernel version, that's a matter for 
> kernel-features.h and __ASSUME_* conditionals.)

On a related note: What are the reasons to have arch-specific assembler
versions of many of the synchronization operations?  I would be
surprised if they'd provide a significant performance advantage; has
anyone recent measurements for this?

It seems to me that it would be useful to consolidate the different
versions that exist for the synchronization operations into shared C
code as long as this doesn't make a significant performance difference.
They are all based on atomic operations and futex operations, both of
which we have in C code (especially if we have compilers that support
the C11 memory model).  Or are there other reasons for keeping different
versions that I'm not aware of?


Torvald