tools/power turbostat: prevent infinite loop on migration error path

Turbostat assumed if it can't migrate to a CPU, then the CPU
must have gone off-line and turbostat should re-initialize
with the new topology.

But if turbostat can not migrate because it is restricted by
a cpuset, then it will fail to migrate even after re-initialization,
resulting in an infinite loop.

Spit out a warning when we can't migrate
and endure only 2 re-initialize cycles in a row
before giving up and exiting.

Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 10 insertions, 1 deletions

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 3c063a00f3bf..77e76b11382f 100644
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -656,8 +656,10 @@ int get_counters(struct thread_data *t, struct core_data *c, struct pkg_data *p)
 {
         int cpu = t->cpu_id;
 
-        if (cpu_migrate(cpu))
+        if (cpu_migrate(cpu)) {
+                fprintf(stderr, "Could not migrate to CPU %d\n", cpu);
                 return -1;
+        }
 
         t->tsc = rdtsc();       /* we are running on local CPU of interest */
 
@@ -1088,15 +1090,22 @@ int mark_cpu_present(int cpu)
 void turbostat_loop()
 {
         int retval;
+        int restarted = 0;
 
 restart:
+        restarted++;
+
         retval = for_all_cpus(get_counters, EVEN_COUNTERS);
         if (retval < -1) {
                 exit(retval);
         } else if (retval == -1) {
+                if (restarted > 1) {
+                        exit(retval);
+                }
                 re_initialize();
                 goto restart;
         }
+        restarted = 0;
         gettimeofday(&tv_even, (struct timezone *)NULL);
 
         while (1) {