cpufreq-scaling-detect: describe cpufreq offline CPU error

jty2 · jty2 · commit f46ade750a83 · 2025-07-31T16:32:13.000-05:00
When cpufreq /sys files are accessed for an offline CPU, errors
about getline() returning -1 are printed.  Describe this in a comment.

Change-Id: I2c6ab8638310aec185b995bcac4b99ffed7a66d1
Signed-off-by: James Yang &lt;james.yang@arm.com&gt;
diff --git a/benchmarks/lockhammer/src/cpufreq-scaling-detect.c b/benchmarks/lockhammer/src/cpufreq-scaling-detect.c
@@ -106,6 +106,10 @@ static char * get_proc_file_first_line (const char * filename) {
         return line;
     }
 
+    // An offline CPU still has the cpufreq pseudo file present with read
+    // permissions, but "Device or resource busy" when accessed, so getline
+    // returns -1.
+
     fprintf(stderr, "unexpectedly getline() returned -1 from reading %s\n", filename);
 
     free(line);

Original file line number	Diff line number	Diff line change
`@@ -106,6 +106,10 @@ static char * get_proc_file_first_line (const char * filename) {`
`106`	`106`	`return line;`
`107`	`107`	`}`
`108`	`108`
	`109`	`+ // An offline CPU still has the cpufreq pseudo file present with read`
	`110`	`+ // permissions, but "Device or resource busy" when accessed, so getline`
	`111`	`+ // returns -1.`
	`112`	`+`
`109`	`113`	`fprintf(stderr, "unexpectedly getline() returned -1 from reading %s\n", filename);`
`110`	`114`
`111`	`115`	`free(line);`