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

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Message-Id: <20170705235738.GK2393@linux.vnet.ibm.com>
Date:   Wed, 5 Jul 2017 16:57:38 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        parri.andrea@...il.com, dave@...olabs.net,
        manfred@...orfullife.com, arnd@...db.de, peterz@...radead.org,
        netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        will.deacon@....com, oleg@...hat.com, mingo@...hat.com,
        netfilter-devel@...r.kernel.org, tj@...nel.org,
        stern@...land.harvard.edu, akpm@...ux-foundation.org,
        torvalds@...ux-foundation.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH RFC 21/26] powerpc: Remove spin_unlock_wait()
 arch-specific definitions

On Sun, Jul 02, 2017 at 11:58:07AM +0800, Boqun Feng wrote:
> On Thu, Jun 29, 2017 at 05:01:29PM -0700, Paul E. McKenney wrote:
> > 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>
> 
> Acked-by: Boqun Feng <boqun.feng@...il.com>

And finally applied in preparation for v2 of the patch series.

Thank you!!!

							Thanx, Paul

> Regards,
> Boqun
> 
> > ---
> >  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
> >