linux-kernel - [PATCH] turbostat: Use sched_getcpu() instead of hardcoded cpu 0

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Message-Id: <20200629192657.34045-1-prarit@redhat.com>
Date:   Mon, 29 Jun 2020 15:26:57 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Prarit Bhargava <prarit@...hat.com>, Len Brown <lenb@...nel.org>,
        linux-pm@...r.kernel.org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH] turbostat: Use sched_getcpu() instead of hardcoded cpu 0

Disabling cpu 0 results in an error

turbostat: /sys/devices/system/cpu/cpu0/topology/thread_siblings: open failed: No such file or directory

Use sched_getcpu() instead of a hardcoded cpu 0 to get the max cpu number.

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: Len Brown <lenb@...nel.org>
Cc: linux-pm@...r.kernel.org
Cc: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
---
 tools/power/x86/turbostat/turbostat.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 33b370865d16..2d3a3012f2f8 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -2769,12 +2769,19 @@ void re_initialize(void)
 void set_max_cpu_num(void)
 {
 	FILE *filep;
+	int base_cpu;
 	unsigned long dummy;
+	char pathname[64];
 
+	base_cpu = sched_getcpu();
+	if (base_cpu < 0)
+		err(1, "cannot find calling cpu ID");
+	sprintf(pathname,
+		"/sys/devices/system/cpu/cpu%d/topology/thread_siblings",
+		base_cpu);
+
+	filep = fopen_or_die(pathname, "r");
 	topo.max_cpu_num = 0;
-	filep = fopen_or_die(
-			"/sys/devices/system/cpu/cpu0/topology/thread_siblings",
-			"r");
 	while (fscanf(filep, "%lx,", &dummy) == 1)
 		topo.max_cpu_num += BITMASK_SIZE;
 	fclose(filep);
-- 
2.21.3