linux-kernel - RE: [RFC 1/2] lib, Make gen_pool memory allocator lockless

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Date:	Wed, 9 Feb 2011 11:03:35 -0800
From:	"Luck, Tony" <tony.luck@...el.com>
To:	"Huang, Ying" <ying.huang@...el.com>, Len Brown <lenb@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: RE: [RFC 1/2] lib, Make gen_pool memory allocator lockless

+static int set_bits_ll(unsigned long *addr, unsigned long mask_to_set)
+{
+	unsigned long val, nval;
+
+	nval = *addr;
+	do {
+		val = nval;
+		if (val & mask_to_set)
+			return -EBUSY;
+	} while ((nval = cmpxchg(addr, val, val | mask_to_set)) != val);
+
+	return 0;
+}

Spin loops like this should have a call to cpu_relax(), shouldn't they?

-Tony
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