[LTP] [PATCH] cpufreq_intel: Check for per-CPU online file presence before reading

[Wake Liu]

From: Grzegorz Jaszczyk <jaszczyk@google.com>

In setup(), the test assumes that all secondary CPUs (cpu1..cpuN-1)
expose '/sys/devices/system/cpu/cpu<N>/online' and attempts to read
their status using SAFE_FILE_SCANF().

However, on systems where CPU hotplugging is disabled (e.g. kernels
built without CONFIG_HOTPLUG_CPU or platforms where CPUs are not
hotpluggable), the per-CPU 'online' sysfs attributes are not created.
Calling SAFE_FILE_SCANF() on a non-existent file results in ENOENT
and breaks test setup with TBROK.

Check for the existence of the per-CPU 'online' file with access()
first. If the file exists, read the status via SAFE_FILE_SCANF(); if
it does not exist, assume the CPU is not hotpluggable and is
permanently online.

Signed-off-by: Grzegorz Jaszczyk <jaszczyk@google.com>
Signed-off-by: Wake Liu <wakel@google.com>
---
 testcases/kernel/power_management/cpufreq_intel.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/power_management/cpufreq_intel.c b/testcases/kernel/power_management/cpufreq_intel.c
index 11896258e..a2a3f3475 100644
--- a/testcases/kernel/power_management/cpufreq_intel.c
+++ b/testcases/kernel/power_management/cpufreq_intel.c
@@ -94,8 +94,16 @@ static void setup(void)
 		int tmp;
 
 		snprintf(path, sizeof(path), "/sys/devices/system/cpu/cpu%d/online", i);
-		SAFE_FILE_SCANF(path, "%d", &tmp);
-		online[i] = (bool)tmp;
+		if (access(path, F_OK) == 0) {
+			SAFE_FILE_SCANF(path, "%d", &tmp);
+			online[i] = (bool)tmp;
+		} else {
+			/*
+			 * If the 'online' file is missing, the CPU is not
+			 * hotpluggable and is permanently online.
+			 */
+			online[i] = true;
+		}
 	}
 
 	SAFE_FILE_PRINTF("/sys/devices/system/cpu/intel_pstate/status", "active");
-- 
2.55.0.897.gb25b4bd76c-goog