linux-kernel - [PATCH RFC 21/26] powerpc: Remove spin_unlock

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Message-Id: <1498780894-8253-21-git-send-email-paulmck@linux.vnet.ibm.com>
Date:   Thu, 29 Jun 2017 17:01:29 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
        oleg@...hat.com, akpm@...ux-foundation.org, mingo@...hat.com,
        dave@...olabs.net, manfred@...orfullife.com, tj@...nel.org,
        arnd@...db.de, linux-arch@...r.kernel.org, will.deacon@....com,
        peterz@...radead.org, stern@...land.harvard.edu,
        parri.andrea@...il.com, torvalds@...ux-foundation.org,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        <linuxppc-dev@...ts.ozlabs.org>
Subject: [PATCH RFC 21/26] powerpc: Remove spin_unlock_wait() arch-specific definitions

There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair.  This commit therefore removes the underlying arch-specific
arch_spin_unlock_wait().

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: <linuxppc-dev@...ts.ozlabs.org>
Cc: Will Deacon <will.deacon@....com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Andrea Parri <parri.andrea@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
---
 arch/powerpc/include/asm/spinlock.h | 33 ---------------------------------
 1 file changed, 33 deletions(-)

diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 8c1b913de6d7..d256e448ea49 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -170,39 +170,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
 	lock->slock = 0;
 }
 
-static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
-{
-	arch_spinlock_t lock_val;
-
-	smp_mb();
-
-	/*
-	 * Atomically load and store back the lock value (unchanged). This
-	 * ensures that our observation of the lock value is ordered with
-	 * respect to other lock operations.
-	 */
-	__asm__ __volatile__(
-"1:	" PPC_LWARX(%0, 0, %2, 0) "\n"
-"	stwcx. %0, 0, %2\n"
-"	bne- 1b\n"
-	: "=&r" (lock_val), "+m" (*lock)
-	: "r" (lock)
-	: "cr0", "xer");
-
-	if (arch_spin_value_unlocked(lock_val))
-		goto out;
-
-	while (lock->slock) {
-		HMT_low();
-		if (SHARED_PROCESSOR)
-			__spin_yield(lock);
-	}
-	HMT_medium();
-
-out:
-	smp_mb();
-}
-
 /*
  * Read-write spinlocks, allowing multiple readers
  * but only one writer.
-- 
2.5.2