Re: [PATCH] Document Linux's memory barriers

• To: Paul Mackerras <[email protected]>
• Subject: Re: [PATCH] Document Linux's memory barriers
• From: Nick Piggin <[email protected]>
• Date: Wed, 08 Mar 2006 18:41:30 +1100
• Cc: David Howells <[email protected]>, [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
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• In-reply-to: <[email protected]>
• References: <[email protected]> <[email protected]>
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Paul Mackerras wrote:

David Howells writes:

+     The way to deal with this is to insert an I/O memory barrier between the
+     two accesses:
+
+	*ADR = ctl_reg_3;
+	mb();
+	reg = *DATA;

Ummm, this implies mb() is "an I/O memory barrier".  I can see people
getting confused if they read this and then see mb() being used when
no I/O is being done.

Isn't it? Why wouldn't you just use smp_mb() if no IO is being done?

--
SUSE Labs, Novell Inc.

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• References:
  • [PATCH] Document Linux's memory barriers
    • From: David Howells <[email protected]>
  • Re: [PATCH] Document Linux's memory barriers
    • From: Paul Mackerras <[email protected]>

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