Extended testing of quad core configuration revealed that this fix was
insufficient. Specifically LTP open posix shm_op/23-1 would cause the
hardware livelock in llock/scond loop in update_cpu_load_active()

So remove this and make way for a proper workaround

This reverts commit a5c8b52a.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

A quad core SMP build could get into hardware livelock with concurrent
LLOCK/SCOND. Workaround that by adding a PREFETCHW which is serialized by
SCU (System Coherency Unit). It brings the cache line in Exclusive state
and makes others invalidate their lines. This gives enough time for
winner to complete the LLOCK/SCOND, before others can get the line back.

The prefetchw in the ll/sc loop is not nice but this is the only
software workaround for current version of RTL.

Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

 - arch_spin_lock/unlock were lacking the ACQUIRE/RELEASE barriers
   Since ARCv2 only provides load/load, store/store and all/all, we need
   the full barrier

 - LLOCK/SCOND based atomics, bitops, cmpxchg, which return modified
   values were lacking the explicit smp barriers.

 - Non LLOCK/SCOND varaints don't need the explicit barriers since that
   is implicity provided by the spin locks used to implement the
   critical section (the spin lock barriers in turn are also fixed in
   this commit as explained above

Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Fixes: f7d11e93 locking,arch,arc: Fold atomic_ops
Cc: <stable@kernel.vger.org> # 3.18
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Verified by doing make headers_install as none of these files are
exported to userspace

Many of the atomic op implementations are the same except for one
instruction; fold the lot into a few CPP macros and reduce LoC.

This also prepares for easy addition of new ops.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Link: http://lkml.kernel.org/r/20140508135851.886055622@infradead.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The arc mb() implementation is a compiler barrier(), therefore it all
doesn't matter one way or the other. Simply remove the existing
definitions and use whatever is generated by the defaults.
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-ua48a59wri3ybz1rz8i7uvbr@git.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Move the barriers functions that depend on the atomic implementation
into the atomic implementation.
Reviewed-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: Vineet Gupta <vgupta@synopsys.com> [for arch/arc bits]
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20131213150640.786183683@infradead.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

This covers the UP / SMP (with no hardware assist for atomic r-m-w) as
well as ARC700 LLOCK/SCOND insns based.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>