Author: Armin Rigo <[email protected]>
Branch: stm-thread-2
Changeset: r61321:effc55eb6a11
Date: 2013-02-16 15:43 +0100
http://bitbucket.org/pypy/pypy/changeset/effc55eb6a11/
Log: Probably fix stm_PtrEq, to never cause transaction aborts.
diff --git a/rpython/translator/stm/src_stm/et.c
b/rpython/translator/stm/src_stm/et.c
--- a/rpython/translator/stm/src_stm/et.c
+++ b/rpython/translator/stm/src_stm/et.c
@@ -676,22 +676,95 @@
/************************************************************/
-inline static gcptr GlobalizeForComparison(struct tx_descriptor *d, gcptr P)
+inline static _Bool _PtrEq_Globals(gcptr G1, gcptr G2)
{
- if (P != NULL && (P->h_tid & (GCFLAG_GLOBAL | GCFLAG_LOCAL_COPY)))
+ /* This is a bit lengthy, but (probably) efficient: the idea is to
+ check if G1 and G2 are pointers in the same chained list of globals
+ or not. Assumes no partial sharing in the chained lists. Works by
+ trying to search forward with S1, starting from G1, if it reaches
+ G2; and conversely with S2, starting from G2, if it reaches G1. */
+ gcptr S1 = G1, S2 = G2;
+ volatile revision_t *vp;
+ revision_t v;
+
+ while (1)
{
- if (P->h_tid & GCFLAG_GLOBAL)
- P = LatestGlobalRevision(d, P, NULL, 0);
- else
- P = (gcptr)P->h_revision; // LOCAL_COPY: return the original global obj
+ if (S2 == G1)
+ return 1;
+
+ /* move forward S1 */
+ vp = (volatile revision_t *)&S1->h_revision;
+ v = *vp;
+ if (v & 1) // "is not a pointer", i.e.
+ goto s1_end; // "doesn't have a more recent revision"
+ S1 = (gcptr)v;
+
+ if (S1 == G2)
+ return 1;
+
+ /* move forward S2 */
+ vp = (volatile revision_t *)&S2->h_revision;
+ v = *vp;
+ if (v & 1) // "is not a pointer", i.e.
+ goto s2_end; // "doesn't have a more recent revision"
+ S2 = (gcptr)v;
}
- return P;
+
+ s1_end:
+ while (1)
+ {
+ /* move forward S2 */
+ vp = (volatile revision_t *)&S2->h_revision;
+ v = *vp;
+ if (v & 1) // "is not a pointer", i.e.
+ return 0; // "doesn't have a more recent revision"
+ S2 = (gcptr)v;
+
+ if (S2 == G1)
+ return 1;
+ }
+
+ s2_end:
+ while (1)
+ {
+ /* move forward S1 */
+ vp = (volatile revision_t *)&S1->h_revision;
+ v = *vp;
+ if (v & 1) // "is not a pointer", i.e.
+ return 0; // "doesn't have a more recent revision"
+ S1 = (gcptr)v;
+
+ if (S1 == G2)
+ return 1;
+ }
}
_Bool stm_PtrEq(gcptr P1, gcptr P2)
{
- struct tx_descriptor *d = thread_descriptor;
- return GlobalizeForComparison(d, P1) == GlobalizeForComparison(d, P2);
+ if (P1 == P2)
+ return 1;
+ else if (P1 == NULL || P2 == NULL) /* and not P1 == P2 == NULL */
+ return 0;
+
+ if (P1->h_tid & GCFLAG_GLOBAL)
+ {
+ if (P2->h_tid & GCFLAG_GLOBAL)
+ return _PtrEq_Globals(P1, P2);
+ else if (P2->h_tid & GCFLAG_LOCAL_COPY)
+ return _PtrEq_Globals(P1, (gcptr)P2->h_revision);
+ else
+ return 0; /* P1 is global, P2 is new */
+ }
+ /* P1 is local, i.e. either new or a local copy */
+ if (P2->h_tid & GCFLAG_GLOBAL)
+ {
+ if (P1->h_tid & GCFLAG_LOCAL_COPY)
+ return _PtrEq_Globals((gcptr)P1->h_revision, P2);
+ else
+ return 0; /* P1 is new, P2 is global */
+ }
+ /* P1 and P2 are both locals (and P1 != P2) */
+ return 0;
}
/************************************************************/
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