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Use what we really mean (powerpc_lwsync()) rather than the Linux-compat

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mb() here and provide some more documentation on what, exactly, makes this
code safe.

Requested by and discussed with:	kib, alc
This commit is contained in:
nwhitehorn 2015-11-24 16:10:21 +00:00
parent a02e9843fe
commit 745b5bcad4
1 changed files with 8 additions and 2 deletions

10
sys/powerpc/aim/slb.c

@ -140,7 +140,7 @@ make_new_leaf(uint64_t esid, uint64_t slbv, struct slbtnode *parent)
* 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 slbtnode *parent)
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_offset_t va)
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)