kern/182999: commit references a PR

[dfilter service]

The following reply was made to PR kern/182999; it has been noted by GNATS.

From: ***@FreeBSD.ORG (dfilter service)
To: bug-***@FreeBSD.org
Cc:
Subject: Re: kern/182999: commit references a PR
Date: Mon, 20 Jan 2014 18:37:47 +0000 (UTC)

Author: marcel
Date: Mon Jan 20 18:37:35 2014
New Revision: 260914
URL: http://svnweb.freebsd.org/changeset/base/260914

Log:
In pmap_set_pte(), make sure to enforce ordering by inserting a memory
fence. Under system load, the CPU has been found to change the order
by which the stores are made visible. When the tag is made visible
before the other TLB values, other CPUs may use the invalid TLB values
and do bad things.

While here (i.e. not a fix) don't return errors from pmap_remove_vhpt()
to callers of pmap_remove_pte(). Those callers don't check the return
value and as such don't do what is needed to keep a consistent state.
More importantly, pmap_remove_vhpt() can't really have an error without
it indicating something unintended. Using KASSERT is therefore better.

PR: 182999, 183227

Modified:
head/sys/ia64/ia64/pmap.c

Modified: head/sys/ia64/ia64/pmap.c
==============================================================================
--- head/sys/ia64/ia64/pmap.c Mon Jan 20 18:15:06 2014 (r260913)
+++ head/sys/ia64/ia64/pmap.c Mon Jan 20 18:37:35 2014 (r260914)
@@ -1303,6 +1303,8 @@ pmap_set_pte(struct ia64_lpte *pte, vm_o

pte->itir = PAGE_SHIFT << 2;

+ ia64_mf();
+
pte->tag = ia64_ttag(va);
}

@@ -1321,8 +1323,8 @@ pmap_remove_pte(pmap_t pmap, struct ia64
* First remove from the VHPT.
*/
error = pmap_remove_vhpt(va);
- if (error)
- return (error);
+ KASSERT(error == 0, ("%s: pmap_remove_vhpt returned %d",
+ __func__, error));

pmap_invalidate_page(va);

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