Clarify terminolgy around cpu ids and array length

[lttng-ust.git] / src / common / smp.h

diff --git a/src/common/smp.h b/src/common/smp.h
index b6dd5707819af414a4c4a203e1e3d998ad983cf3..f908b6c6ef39c5e9f8868ec15b19a78f80b54d83 100644 (file)
--- a/src/common/smp.h
+++ b/src/common/smp.h
@@ -7,6 +7,8 @@
 #ifndef _UST_COMMON_SMP_H
 #define _UST_COMMON_SMP_H
 
+#define LTTNG_UST_CPUMASK_SIZE 4096
+
 /*
  * Get the CPU possible mask string from sysfs.
  *
@@ -28,27 +30,31 @@ int get_num_possible_cpus_fallback(void)
        __attribute__((visibility("hidden")));
 
 /*
- * Get the number of CPUs from the possible cpu mask.
+ * Get the highest CPU id from a CPU mask.
  *
  * pmask: the mask to parse.
  * len: the len of the mask excluding '\0'.
  *
- * Returns the number of possible CPUs from the mask or 0 on error.
+ * Returns the highest CPU id from the mask or -1 on error.
  */
-int get_num_possible_cpus_from_mask(const char *pmask, size_t len)
+int get_max_cpuid_from_mask(const char *pmask, size_t len)
        __attribute__((visibility("hidden")));
 
 /*
- * Returns the total number of CPUs in the system. If the cache is not yet
- * initialized, get the value from "/sys/devices/system/cpu/possible" or
- * fallback to sysconf and cache it.
+ * Returns the length of an array that could contain a per-CPU element for each
+ * possible CPU id for the lifetime of the process.
+ *
+ * We currently assume CPU ids are contiguous up the maximum CPU id.
+ *
+ * If the cache is not yet initialized, get the value from
+ * "/sys/devices/system/cpu/possible" or fallback to sysconf and cache it.
  *
  * If all methods fail, don't populate the cache and return 0.
  */
-int num_possible_cpus(void)
+int get_possible_cpus_array_len(void)
        __attribute__((visibility("hidden")));
 
 #define for_each_possible_cpu(cpu)             \
-       for ((cpu) = 0; (cpu) < num_possible_cpus(); (cpu)++)
+       for ((cpu) = 0; (cpu) < get_possible_cpus_array_len(); (cpu)++)
 
 #endif /* _UST_COMMON_SMP_H */