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[RFC][PATCH 5/5] powerpc: Remove SYNC from _switch

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Now that the scheduler's rq->lock is RCsc and thus provides full
transitivity between scheduling actions. And since we cannot migrate
current, a task needs a switch-out and a switch-in in order to
migrate, in which case the RCsc provides all the ordering we need.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/powerpc/kernel/entry_64.S |    8 --------
 1 file changed, 8 deletions(-)

--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -488,14 +488,6 @@ _GLOBAL(_switch)
 	std	r23,_CCR(r1)
 	std	r1,KSP(r3)	/* Set old stack pointer */
 
-#ifdef CONFIG_SMP
-	/* We need a sync somewhere here to make sure that if the
-	 * previous task gets rescheduled on another CPU, it sees all
-	 * stores it has performed on this one.
-	 */
-	sync
-#endif /* CONFIG_SMP */
-
 	/*
 	 * If we optimise away the clear of the reservation in system
 	 * calls because we know the CPU tracks the address of the

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[RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 2/5] locking: Introduce smp_mb__after_spinlock(). Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
    Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Will Deacon <will.deacon@arm.com> - 2017-06-09 16:50 +0200
      Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending() Peter Zijlstra <peterz@infradead.org> - 2017-06-09 20:50 +0200
  [RFC][PATCH 3/5] overlayfs: Remove smp_mb__before_spinlock() usage Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 4/5] locking: Remove smp_mb__before_spinlock() Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
  [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-07 18:30 +0200
    Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 02:40 +0200
      Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 09:00 +0200
        Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 09:40 +0200
          Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 10:00 +0200
            Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 10:30 +0200
            Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Michael Ellerman <mpe@ellerman.id.au> - 2017-06-08 12:00 +0200
              Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 12:10 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 14:50 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Nicholas Piggin <npiggin@gmail.com> - 2017-06-08 15:20 +0200
                Re: [RFC][PATCH 5/5] powerpc: Remove SYNC from _switch Peter Zijlstra <peterz@infradead.org> - 2017-06-08 15:50 +0200
  Re: [RFC][PATCH 0/5] Getting rid of smp_mb__before_spinlock Will Deacon <will.deacon@arm.com> - 2017-06-09 17:00 +0200

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