linux-kernel - [PATCH] perf tools: handle TOPOLOGY headers with no CPU

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Date:   Sat, 19 Jan 2019 00:12:39 -0800
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...hat.com, jolsa@...hat.com, peterz@...radead.org,
        mingo@...e.hu, ak@...ux.intel.com, kan.liang@...el.com
Subject: [PATCH] perf tools: handle TOPOLOGY headers with no CPU

This patch fixes an issue in cpumap.c when used with the
TOPOLOGY header. In some configurations, some NUMA nodes may
have no CPU (empty cpulist). Yet a cpumap map must be created
otherwise perf abort with an error. This patch handles this
case by creating a dummy map.

Before:
$ perf record -o - -e cycles noploop 2 | perf script -i -
0x6e8 [0x6c]: failed to process type: 80

After:
$ perf record -o - -e cycles noploop 2 | perf script -i -
noploop for 2 seconds

Signed-off-by: Stephane Eranian <eranian@...gle.com>
---
 tools/perf/util/cpumap.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
index 1ccbd3342069..383674f448fc 100644
--- a/tools/perf/util/cpumap.c
+++ b/tools/perf/util/cpumap.c
@@ -134,7 +134,12 @@ struct cpu_map *cpu_map__new(const char *cpu_list)
 	if (!cpu_list)
 		return cpu_map__read_all_cpu_map();
 
-	if (!isdigit(*cpu_list))
+	/*
+	 * must handle the case of empty cpumap to cover
+	 * TOPOLOGY header for NUMA nodes with no CPU
+	 * ( e.g., because of CPU hotplug)
+	 */
+	if (!isdigit(*cpu_list) && *cpu_list != '\0')
 		goto out;
 
 	while (isdigit(*cpu_list)) {
@@ -181,8 +186,10 @@ struct cpu_map *cpu_map__new(const char *cpu_list)
 
 	if (nr_cpus > 0)
 		cpus = cpu_map__trim_new(nr_cpus, tmp_cpus);
-	else
+	else if (*cpu_list != '\0')
 		cpus = cpu_map__default_new();
+	else
+		cpus = cpu_map__dummy_new();
 invalid:
 	free(tmp_cpus);
 out:
-- 
2.7.4