From: Peter Zijlstra <peterz@infradead•org>
To: Michael Ellerman <mpe@ellerman•id.au>
Cc: linuxppc-dev@lists•ozlabs.org,
Linux Kernel Mailing List <linux-kernel@vger•kernel.org>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Paul Mackerras <paulus@samba•org>,
"Paul E. McKenney" <paulmck@linux•vnet.ibm.com>,
Will Deacon <will.deacon@arm•com>,
Boqun Feng <boqun.feng@gmail•com>
Subject: Re: [PATCH v3] powerpc: spinlock: Fix spin_unlock_wait()
Date: Mon, 6 Jun 2016 16:46:59 +0200 [thread overview]
Message-ID: <20160606144659.GG30909@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1465215445.2658.4.camel@ellerman.id.au>
On Mon, Jun 06, 2016 at 10:17:25PM +1000, Michael Ellerman wrote:
> On Mon, 2016-06-06 at 13:56 +0200, Peter Zijlstra wrote:
> > On Mon, Jun 06, 2016 at 09:42:20PM +1000, Michael Ellerman wrote:
> > > +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 (!arch_spin_value_unlocked(*lock)) {
> > > + HMT_low();
> > > + if (SHARED_PROCESSOR)
> > > + __spin_yield(lock);
> > > + }
> > > + HMT_medium();
> > > +
> > > +out:
> > > + smp_mb();
> > > +}
> >
> > Why the move to in-line this implementation? It looks like a fairly big
> > function.
>
> I agree it's not pretty.
>
> I'm not beholden to v3 though if you hate it.
I don't mind; its just that I am in a similar boat with qspinlock and
chose the other option. So I just figured I'd ask :-)
next prev parent reply other threads:[~2016-06-06 14:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 11:42 [PATCH v3] powerpc: spinlock: Fix spin_unlock_wait() Michael Ellerman
2016-06-06 11:56 ` Peter Zijlstra
2016-06-06 12:17 ` Michael Ellerman
2016-06-06 14:46 ` Peter Zijlstra [this message]
2016-06-08 11:20 ` Michael Ellerman
2016-06-08 12:35 ` Peter Zijlstra
2016-06-08 13:49 ` Michael Ellerman
2016-06-08 13:59 ` Peter Zijlstra
2016-06-09 12:23 ` Michael Ellerman
2016-06-09 17:25 ` Boqun Feng
2016-06-10 3:06 ` Boqun Feng
2016-06-09 17:50 ` Peter Zijlstra
2016-06-10 0:57 ` Michael Ellerman
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