tuning: Avoid crash in PerformancePowerProfile

The current code do not check if the scaling_governor is present before
using it, leading to a crash.

To improve this part of the code, this commit is:
- considering the current_governor instead of the available ones to
  decide if the tuning should be done
- adding a check before actually reading the scaling governor file and
  ignore the function if no file found

This commit fixes issue #25.

Signed-off-by: Erwan Velu <[email protected]>

hwbench/tuning/power_profile.py

@@ -10,15 +10,13 @@ def __init__(self, out_dir):
         self.out_dir = out_dir
         self.skip_tuning = False
 
-        available_governors = (
-            pathlib.Path("/sys/devices/system/cpu/cpuidle/available_governors")
+        current_governor = (
+            pathlib.Path("/sys/devices/system/cpu/cpuidle/current_governor")
             .read_text("ascii")
             .strip()
             .split()
         )
-        self.skip_tuning |= (
-            len(available_governors) == 1 and available_governors[0] == "menu"
-        )
+        self.skip_tuning |= current_governor == "menu"
 
     def run(self) -> None:
         log = tunninglog()
@@ -29,8 +27,15 @@ def run(self) -> None:
         for rootpath, dirnames, filenames in os.walk("/sys/devices/system/cpu"):
             for dirname in dirnames:
                 if pattern.match(dirname):
-                    cpudir = pathlib.Path(rootpath) / dirname
-                    file = cpudir / "cpufreq/scaling_governor"
+                    file = pathlib.Path(rootpath).joinpath(
+                        dirname, "cpufreq", "scaling_governor"
+                    )
+                    # Ignore this tuning if no scaling_governor available
+                    if not file.exists():
+                        log.info(
+                            f"skip PerformancePowerProfile for {dirname} as no scaling governor detected"
+                        )
+                        continue
                     previous = file.read_text(encoding="utf-8").rstrip()
                     # please read https://www.kernel.org/doc/html/latest/admin-guide/pm/cpufreq.html
                     # for more explanation