[PATCH] Clean up BUSY_WAIT_NOP and atomic_delay.

[Torvald Riegel]

This patch combines BUSY_WAIT_NOP and atomic_delay into a new
atomic_spin_nop function and adjusts all clients.  The new function is
put into atomic.h because what is best done in a spin loop is
architecture-specific, and atomics must be used for spinning.  The
function name is meant to tell users that this has no effect on
synchronization semantics but is a performance aid for spinning.

Roland, this removes the NaCl definitions of spinning because they
should be primarily architecture-dependent.  I don't know whether you're
doing something really advanced with spinning yet that would be NaCl
specific, but then this would be future work anyway and would likely
involve a custom implementation of a whole spin loop and the
accompanying futex wait call.  If so, we can address this later.

Dave, can you check the sparc bits please?  I believe I just moved code
around, but I can't test this easily.

Tested on x86_64-linux.


2015-06-23  Torvald Riegel  <triegel@redhat.com>

	* sysdeps/unix/sysv/linux/i386/lowlevellock.h (BUSY_WAIT_NOP): Remove.
	* sysdeps/unix/sysv/linux/x86_64/lowlevellock.h (BUSY_WAIT_NOP):
	Likewise.
	* sysdeps/i386/i486/bits/atomic.h (atomic_delay): Rename to
	atomic_spin_nop.
	* sysdeps/x86_64/bits/atomic.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/lowlevellock.h (BUSY_WAIT_NOP): Rename
	to atomic_spin_nop and move ...
	* sysdeps/sparc/sparc32/sparcv9/bits/atomic.h (atomic_spin_nop):
	... here and ...
	* sysdeps/sparc/sparc64/bits/atomic.h: ... here.
	* nptl/pthread_mutex_lock.c (__pthread_mutex_lock): Use
	atomic_spin_nop instead of BUSY_WAIT_NOP.
	* nptl/pthread_mutex_timedlock.c (__pthread_mutex_timedlock):
	Likewise.
	* sysdeps/nacl/lll_timedwait_tid.c (__lll_timedwait_tid): Likewise.
	* sysdeps/nacl/lowlevellock.h (BUSY_WAIT_NOP): Remove.
	(lll_wait_tid): Use atomic_spin_nop instead of BUSY_WAIT_NOP.
	* nscd/nscd-client.h (__nscd_acquire_maplock): Use atomic_spin_nop
	instead of atomic_delay.
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