commit 6de699f68e6e2bffb44a1b943aca52d7d838d4d4
Author: Vince Weaver <vincent.weaver@maine.edu>
Date:   Thu Jan 10 14:54:42 2019 -0500

    perf_event: internally indicate we need fallback when rdpmc not available

diff --git a/src/components/perf_event/perf_helpers.h b/src/components/perf_event/perf_helpers.h
index 20dfbacd1..7f0ff6c95 100644
--- a/src/components/perf_event/perf_helpers.h
+++ b/src/components/perf_event/perf_helpers.h
@@ -138,6 +138,10 @@ static inline unsigned long long mmap_read_self(void *addr,
 
 			/* Only adjust if index is valid */
 			running+=delta;
+		} else {
+			/* Falling back because rdpmc not supported	*/
+			/* for this event.				*/
+			return 0xffffffffffffffffULL;
 		}
 
 		barrier();
commit a76b1580f035726b28b0e37afc75de760ceaf1e4
Author: Vince Weaver <vincent.weaver@maine.edu>
Date:   Thu Jan 10 15:36:03 2019 -0500

    perf_event: properly fall back to read() if rdpmc read attempt fails
    
    The code wasn't properly handling this.
    
    We now fall back to read() if *any* rdpmc call in an eventset fails.
    In theory it is possible to only fall back in a per-event fashion but
    that would make the code a lot more complex.

diff --git a/src/components/perf_event/perf_event.c b/src/components/perf_event/perf_event.c
index a3bd0b800..1f4bbcee7 100644
--- a/src/components/perf_event/perf_event.c
+++ b/src/components/perf_event/perf_event.c
@@ -1094,6 +1094,7 @@ _pe_rdpmc_read( hwd_context_t *ctx, hwd_control_state_t *ctl,
 	int i;
 	pe_control_t *pe_ctl = ( pe_control_t *) ctl;
 	unsigned long long count, enabled, running, adjusted;
+	int errors=0;
 
 	/* we must read each counter individually */
 	for ( i = 0; i < pe_ctl->num_events; i++ ) {
@@ -1101,7 +1102,9 @@ _pe_rdpmc_read( hwd_context_t *ctx, hwd_control_state_t *ctl,
 		count = mmap_read_self(pe_ctl->events[i].mmap_buf,
 						&enabled,&running);
 
-		/* TODO: more error checking? */
+		if (count==0xffffffffffffffffULL) {
+			errors++;
+		}
 
 		/* Handle multiplexing case */
 		if (enabled == running) {
@@ -1127,6 +1130,8 @@ _pe_rdpmc_read( hwd_context_t *ctx, hwd_control_state_t *ctl,
 
 	SUBDBG("EXIT: *events: %p\n", *events);
 
+	if (errors) return PAPI_ESYS;
+
 	return PAPI_OK;
 }
 
@@ -1253,10 +1258,16 @@ _pe_read( hwd_context_t *ctx, hwd_control_state_t *ctl,
 	int i, j, ret = -1;
 	pe_control_t *pe_ctl = ( pe_control_t *) ctl;
 	long long papi_pe_buffer[READ_BUFFER_SIZE];
+	int result;
 
 	/* Handle fast case */
+	/* FIXME: we fallback to slow reads if *any* event in eventset fails */
+	/*        in theory we could only fall back for the one event        */
+	/*        but that makes the code more complicated.                  */
 	if ((_perf_event_vector.cmp_info.fast_counter_read) && (!pe_ctl->inherit)) {
-		return _pe_rdpmc_read( ctx, ctl, events, flags);
+		result=_pe_rdpmc_read( ctx, ctl, events, flags);
+		/* if successful we are done, otherwise fall back to read */
+		if (result==PAPI_OK) return PAPI_OK;
 	}
 
 	/* Handle case where we are multiplexing */