Author: nwhitehorn
Date: Tue Nov 24 16:10:21 2015
New Revision: 291262
URL: https://svnweb.freebsd.org/changeset/base/291262
Log:
Use what we really mean (powerpc_lwsync()) rather than the Linux-compat
mb() here and provide some more documentation on what, exactly, makes this
code safe.
Requested by and discussed with: kib, alc
Modified:
head/sys/powerpc/aim/slb.c
Modified: head/sys/powerpc/aim/slb.c
==============================================================================
--- head/sys/powerpc/aim/slb.c Tue Nov 24 16:07:03 2015 (r291261)
+++ head/sys/powerpc/aim/slb.c Tue Nov 24 16:10:21 2015 (r291262)
@@ -140,7 +140,7 @@ make_new_leaf(uint64_t esid, uint64_t sl
* that a lockless searcher always sees a valid path through
* the tree.
*/
- mb();
+ powerpc_lwsync();
idx = esid2idx(esid, parent->ua_level);
parent->u.ua_child[idx] = child;
@@ -188,7 +188,7 @@ make_intermediate(uint64_t esid, struct
idx = esid2idx(child->ua_base, inter->ua_level);
inter->u.ua_child[idx] = child;
setbit(&inter->ua_alloc, idx);
- mb();
+ powerpc_lwsync();
/* Set up parent to point to intermediate node ... */
idx = esid2idx(inter->ua_base, parent->ua_level);
@@ -241,6 +241,12 @@ user_va_to_slb_entry(pmap_t pm, vm_offse
return ((ua->u.slb_entries[idx].slbe & SLBE_VALID) ?
&ua->u.slb_entries[idx] : NULL);
+ /*
+ * The following accesses are implicitly ordered under the POWER
+ * ISA by load dependencies (the store ordering is provided by
+ * the powerpc_lwsync() calls elsewhere) and so are run without
+ * barriers.
+ */
ua = ua->u.ua_child[idx];
if (ua == NULL ||
esid2base(esid, ua->ua_level) != ua->ua_base)
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