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Subject: Re: [PATCH 1/2] amd76x_pm: C2 powersaving for AMD K7
From: Arjan van de Ven <arjan@infradead.org>
To: Joerg Sommrey <jo@sommrey.de>
Cc: Linux kernel mailing list <linux-kernel@vger.kernel.org>
In-Reply-To: <20060108190337.GA22780@sommrey.de>
References: <20060108190337.GA22780@sommrey.de>
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Date: Sun, 08 Jan 2006 20:10:10 +0100
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On Sun, 2006-01-08 at 20:03 +0100, Joerg Sommrey wrote:
> + * Locking is done using atomic_t variables, no spin locks needed.

but... there seems to be a race now:
+               smp_mb();
+               if (unlikely(atomic_read(&amd76x_stat.num_idle)
+                                       == num_online)) {
+                       /* Invoke C2 */
+                       prs->C2_cnt++;
+                       inb(amd76x_pm_cfg.C2_reg);
+                       break;
+               }


also.. atomic_t + manual interrupt disabling isn't by definition better
than a spinlock... when people say "spinlocks are expensive" they imply
that atomics are also expensive...