X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-context-perf-counters.c;h=a7e1b63f4ab02f5666fbbe3c5c4a23b8dcda5a19;hb=4f58f54fdc949a00a05743ecf6d95144192c2ce2;hp=0b8f9fa2ee27bd1646d3785bc58668ea069063f7;hpb=380a81f4797534d6eadbba24ae80ed50a8e672f8;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-context-perf-counters.c b/liblttng-ust/lttng-context-perf-counters.c
index 0b8f9fa2..a7e1b63f 100644
--- a/liblttng-ust/lttng-context-perf-counters.c
+++ b/liblttng-ust/lttng-context-perf-counters.c
@@ -113,11 +113,17 @@ uint64_t read_perf_counter(
 		cmm_barrier();
 
 		idx = pc->index;
-		if (idx)
-			count = pc->offset + rdpmc(idx - 1);
-		else
+		if (idx) {
+			int64_t pmcval;
+
+			pmcval = rdpmc(idx - 1);
+			/* Sign-extend the pmc register result. */
+			pmcval <<= 64 - pc->pmc_width;
+			pmcval >>= 64 - pc->pmc_width;
+			count = pc->offset + pmcval;
+		} else {
 			count = 0;
-
+		}
 		cmm_barrier();
 	} while (CMM_LOAD_SHARED(pc->lock) != seq);