[SIGAR-102] check kernel version rather than /proc/diskstats to detect nptl

src/os/linux/linux_sigar.c

@@ -23,6 +23,7 @@
 #include <sys/param.h>
 #include <sys/stat.h>
 #include <sys/times.h>
+#include <sys/utsname.h>
 
 #include "sigar.h"
 #include "sigar_private.h"
@@ -45,9 +46,6 @@
 #define PROC_PARTITIONS PROC_FS_ROOT "partitions"
 #define PROC_DISKSTATS  PROC_FS_ROOT "diskstats"
 
-/* Native POSIX Thread Library 2.6+ kernel */
-#define SIGAR_HAS_NPTL (sigar->iostat == IOSTAT_DISKSTATS)
-
 /*
  * /proc/self/stat fields:
  * 1 - pid
@@ -157,7 +155,9 @@ static int sigar_boot_time_get(sigar_t *sigar)
 int sigar_os_open(sigar_t **sigar)
 {
     int i, status;
+    int kernel_rev, has_nptl;
     struct stat sb;
+    struct utsname name;
 
     *sigar = malloc(sizeof(**sigar));
 
@@ -199,6 +199,17 @@ int sigar_os_open(sigar_t **sigar)
     /* hook for using mirrored /proc/net/tcp file */
     (*sigar)->proc_net = getenv("SIGAR_PROC_NET");
 
+    uname(&name);
+    /* 2.X.y.z -> just need X (unless there is ever a kernel version 3!) */
+    kernel_rev = atoi(&name.release[2]);
+    if (kernel_rev >= 6) {
+        has_nptl = 1;
+    }
+    else {
+        has_nptl = getenv("SIGAR_HAS_NPTL") ? 1 : 0;
+    }
+    (*sigar)->has_nptl = has_nptl;
+
     return SIGAR_OK;
 }
 
@@ -585,7 +596,7 @@ int sigar_os_proc_list_get(sigar_t *sigar,
 {
     DIR *dirp = opendir(PROCP_FS_ROOT);
     struct dirent *ent, dbuf;
-    register const int threadbadhack = !SIGAR_HAS_NPTL;
+    register const int threadbadhack = !sigar->has_nptl;
 
     if (!dirp) {
         return errno;

src/os/linux/sigar_os.h

@@ -67,6 +67,8 @@ struct sigar_t {
     int lcpu;
     linux_iostat_e iostat;
     char *proc_net;
+    /* Native POSIX Thread Library 2.6+ kernel */
+    int has_nptl;
 };
 
 #define HAVE_STRERROR_R