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From:   Stephane Eranian <eranian@google.com>
To:     linux-kernel@vger.kernel.org
Cc:     acme@redhat.com, jolsa@redhat.com, peterz@infradead.org,
        mingo@elte.hu, ak@linux.intel.com, kan.liang@intel.com
Subject: [PATCH] perf tools: handle TOPOLOGY headers with no CPU
Date:   Sat, 19 Jan 2019 00:12:39 -0800
Message-Id: <1547885559-1657-1-git-send-email-eranian@google.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@google.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