Module Name: src
Committed By: thorpej
Date: Fri Mar 29 03:11:32 UTC 2019
Modified Files:
src/sys/arch/alpha/alpha: pmap.c
Log Message:
Fix a couple of latent MP issues in the Alpha pmap:
- In pmap_activate(), even though we manipulate the active mask
with atomic ops, the lev1map pointer needs to stay consistent,
so we do, in fact, have to take the pmap lock there.
- In pmap_emulate_reference(), some of the DEBUG checks done here
are race-prone, so don't do them. (Leave them #if 0'd out for
documentary purposes.)
To generate a diff of this commit:
cvs rdiff -u -r1.263 -r1.264 src/sys/arch/alpha/alpha/pmap.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/alpha/alpha/pmap.c
diff -u src/sys/arch/alpha/alpha/pmap.c:1.263 src/sys/arch/alpha/alpha/pmap.c:1.264
--- src/sys/arch/alpha/alpha/pmap.c:1.263 Fri Mar 1 04:29:20 2019
+++ src/sys/arch/alpha/alpha/pmap.c Fri Mar 29 03:11:32 2019
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.c,v 1.263 2019/03/01 04:29:20 mrg Exp $ */
+/* $NetBSD: pmap.c,v 1.264 2019/03/29 03:11:32 thorpej Exp $ */
/*-
* Copyright (c) 1998, 1999, 2000, 2001, 2007, 2008 The NetBSD Foundation, Inc.
@@ -140,7 +140,7 @@
#include <sys/cdefs.h> /* RCS ID & Copyright macro defns */
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.263 2019/03/01 04:29:20 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.264 2019/03/29 03:11:32 thorpej Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -2126,6 +2126,14 @@ pmap_activate(struct lwp *l)
printf("pmap_activate(%p)\n", l);
#endif
+ /*
+ * Lock the pmap across the work we do here; although the
+ * in-use mask is manipulated with an atomic op and the
+ * ASN info is per-cpu, the lev1map pointer needs to remain
+ * consistent across the entire call.
+ */
+ PMAP_LOCK(pmap);
+
/* Mark the pmap in use by this processor. */
atomic_or_ulong(&pmap->pm_cpus, (1UL << cpu_id));
@@ -2133,6 +2141,8 @@ pmap_activate(struct lwp *l)
pmap_asn_alloc(pmap, cpu_id);
PMAP_ACTIVATE(pmap, l, cpu_id);
+
+ PMAP_UNLOCK(pmap);
}
/*
@@ -2140,10 +2150,6 @@ pmap_activate(struct lwp *l)
*
* Mark that the pmap used by the specified process is no longer
* in use by the processor.
- *
- * The comment above pmap_activate() wrt. locking applies here,
- * as well. Note that we use only a single `atomic' operation,
- * so no locking is necessary.
*/
void
pmap_deactivate(struct lwp *l)
@@ -2156,7 +2162,8 @@ pmap_deactivate(struct lwp *l)
#endif
/*
- * Mark the pmap no longer in use by this processor.
+ * Mark the pmap no longer in use by this processor. Because
+ * this is all we're doing, no need to take the pmap lock.
*/
atomic_and_ulong(&pmap->pm_cpus, ~(1UL << cpu_number()));
}
@@ -2635,7 +2642,7 @@ pmap_emulate_reference(struct lwp *l, va
printf("*pte = 0x%lx\n", *pte);
}
#endif
-#ifdef DEBUG /* These checks are more expensive */
+#if 0/*DEBUG*/ /* These checks are, expensive, racy, and unreliable. */
if (!pmap_pte_v(pte))
panic("pmap_emulate_reference: invalid pte");
if (type == ALPHA_MMCSR_FOW) {
