tools/power/cpupower: allow running without cpu0

Linux-3.7 added CONFIG_BOOTPARAM_HOTPLUG_CPU0,
allowing systems to offline cpu0.

But when cpu0 is offline, cpupower monitor will not display all
processor and Mperf information:

[root@intel-skylake-dh-03 cpupower]# ./cpupower monitor
WARNING: at least one cpu is offline
    |Idle_Stats
CPU | POLL | C1-S | C1E- | C3-S | C6-S | C7s- | C8-S
   4|  0.00|  0.00|  0.00|  0.00|  0.90|  0.00| 96.13
   1|  0.00|  0.00|  5.49|  0.00|  0.01|  0.00| 92.26
   5|  0.00|  0.00|  0.00|  0.00|  0.46|  0.00| 99.50
   2| 45.42|  0.00|  0.00|  0.00| 22.94|  0.00| 28.84
   6|  0.00| 37.54|  0.00|  0.00|  0.00|  0.00|  0.00
   3|  0.00|  0.00|  0.00|  0.00|  0.30|  0.00| 91.99
   7|  0.00|  0.00|  0.00|  0.00|  4.70|  0.00|  0.70

This patch replaces the hard-coded use of cpu0 in cpupower with the
current cpu, allowing it to run without a cpu0.

After the patch is applied,

[root@intel-skylake-dh-03 cpupower]# ./cpupower monitor
WARNING: at least one cpu is offline
    |Nehalem                    || Mperf              || Idle_Stats
CPU | C3   | C6   | PC3  | PC6  || C0   | Cx   | Freq || POLL | C1-S | C1E- | C3-S | C6-S | C7s- | C8-S
   4|  0.01|  1.27|  0.00|  0.00||  0.04| 99.96|  3957||  0.00|  0.00|  0.00|  0.00|  1.43|  0.00| 98.52
   1|  0.00| 98.82|  0.00|  0.00||  0.05| 99.95|  3361||  0.00|  0.00|  0.01|  0.00|  0.03|  0.00| 99.88
   5|  0.00| 98.82|  0.00|  0.00||  0.09| 99.91|  3917||  0.00|  0.00|  0.00|  0.00| 99.38|  0.00|  0.50
   2|  0.33|  0.00|  0.00|  0.00||  0.00|100.00|  3890||  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|100.00
   6|  0.33|  0.00|  0.00|  0.00||  0.01| 99.99|  3903||  0.00|  0.00|  0.00|  0.00|  0.00|  0.00| 99.99
   3|  0.01|  0.71|  0.00|  0.00||  0.06| 99.94|  3678||  0.00|  0.00|  0.00|  0.00|  0.80|  0.00| 99.13
   7|  0.01|  0.71|  0.00|  0.00||  0.03| 99.97|  3538||  0.00|  0.69| 11.70|  0.00|  0.00|  0.00| 87.57

There are some minor cleanups included in this patch.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Thomas Renninger <trenn@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/tools/power/cpupower/utils/cpupower.c b/tools/power/cpupower/utils/cpupower.c
index 9ea914378985..2dccf4998599 100644
--- a/tools/power/cpupower/utils/cpupower.c
+++ b/tools/power/cpupower/utils/cpupower.c
@@ -12,6 +12,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#include <sched.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/utsname.h>
@@ -31,6 +32,7 @@ static int cmd_help(int argc, const char **argv);
  */
 struct cpupower_cpu_info cpupower_cpu_info;
 int run_as_root;
+int base_cpu;
 /* Affected cpus chosen by -c/--cpu param */
 struct bitmask *cpus_chosen;
 
@@ -174,6 +176,7 @@ int main(int argc, const char *argv[])
 	unsigned int i, ret;
 	struct stat statbuf;
 	struct utsname uts;
+	char pathname[32];
 
 	cpus_chosen = bitmask_alloc(sysconf(_SC_NPROCESSORS_CONF));
 
@@ -198,17 +201,23 @@ int main(int argc, const char *argv[])
 		argv[0] = cmd = "help";
 	}
 
-	get_cpu_info(0, &cpupower_cpu_info);
+	base_cpu = sched_getcpu();
+	if (base_cpu < 0) {
+		fprintf(stderr, _("No valid cpus found.\n"));
+		return EXIT_FAILURE;
+	}
+
+	get_cpu_info(&cpupower_cpu_info);
 	run_as_root = !geteuid();
 	if (run_as_root) {
 		ret = uname(&uts);
+		sprintf(pathname, "/dev/cpu/%d/msr", base_cpu);
 		if (!ret && !strcmp(uts.machine, "x86_64") &&
-		    stat("/dev/cpu/0/msr", &statbuf) != 0) {
+		    stat(pathname, &statbuf) != 0) {
 			if (system("modprobe msr") == -1)
 	fprintf(stderr, _("MSR access not available.\n"));
 		}
 	}
-		
 
 	for (i = 0; i < ARRAY_SIZE(commands); i++) {
 		struct cmd_struct *p = commands + i;