From: Arnaldo Carvalho de Melo <[email protected]>

That was reproduced via ftrace as described in this cset comment log,
need to investigate further.

Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
 tools/perf/builtin-trace.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index c907e7e..c3caabb 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -298,7 +298,22 @@ static struct syscall *trace__syscall_info(struct trace 
*trace,
        int id = perf_evsel__intval(evsel, sample, "id");
 
        if (id < 0) {
-               fprintf(trace->output, "Invalid syscall %d id, skipping...\n", 
id);
+
+               /*
+                * XXX: Noticed on x86_64, reproduced as far back as 3.0.36, 
haven't tried
+                * before that, leaving at a higher verbosity level till that is
+                * explained. Reproduced with plain ftrace with:
+                *
+                * echo 1 > /t/events/raw_syscalls/sys_exit/enable
+                * grep "NR -1 " /t/trace_pipe
+                *
+                * After generating some load on the machine.
+                */
+               if (verbose > 1) {
+                       static u64 n;
+                       fprintf(trace->output, "Invalid syscall %d id, skipping 
(%s, %" PRIu64 ") ...\n",
+                               id, perf_evsel__name(evsel), ++n);
+               }
                return NULL;
        }
 
-- 
1.8.1.4

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