From: Russell King <rmk@dyn-67.arm.linux.org.uk>
Date: Tue, 8 May 2007 19:03:09 +0000 (+0100)
Subject: [ARM] Fix ASID version switch
X-Git-Tag: v2.6.22-rc1~144^2^3~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8678c1f04277daaa914abb107fb9fe71298d916d;p=pandora-kernel.git

[ARM] Fix ASID version switch

Close a hole in the ASID version switch, particularly the following
scenario:

CPU0 MM PID			CPU1 MM PID
	idle
				  A	pid(A)
				  A	idle(lazy tlb)
		* new asid version triggered by B *
  B	pid(B)
  A	pid(A)
		* MM A gets new asid version *
  A	idle(lazy tlb)
				  A	pid(A)
		* CPU1 doesn't see the new ASID *

The result is that CPU1 continues running with the hardware set
for the original (stale) ASID value, but mm->context.id contains
the new ASID value.  The result is that the next MM fault on CPU1
updates the page table entries, but flush_tlb_page() fails due to
wrong ASID.

There is a related case with a threaded application is allocated
a new ASID on one CPU while another of its threads is running on
some different CPU.  This scenario is not fixed by this commit.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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