Move to kernel style SPDX license identifiers

[lttng-ust.git] / libringbuffer / smp.c

diff --git a/libringbuffer/smp.c b/libringbuffer/smp.c
index 9e7114be8a40f3349b8a8942131f440ce0514311..39bd5559094e75b6305e96f13e8002312f7861c5 100644 (file)
--- a/libringbuffer/smp.c
+++ b/libringbuffer/smp.c
@@ -1,24 +1,10 @@
 /*
- * libringbuffer/smp.c
+ * SPDX-License-Identifier: LGPL-2.1-only
  *
  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
  */
 
-#define _GNU_SOURCE
 #define _LGPL_SOURCE
 #include <unistd.h>
 #include <pthread.h>
@@ -26,6 +12,7 @@
 
 int __num_possible_cpus;
 
+#if (defined(__GLIBC__) || defined( __UCLIBC__))
 void _get_num_possible_cpus(void)
 {
        int result;
@@ -43,3 +30,67 @@ void _get_num_possible_cpus(void)
                return;
        __num_possible_cpus = result;
 }
+
+#else
+
+/*
+ * The MUSL libc implementation of the _SC_NPROCESSORS_CONF sysconf does not
+ * return the number of configured CPUs in the system but relies on the cpu
+ * affinity mask of the current task.
+ *
+ * So instead we use a strategy similar to GLIBC's, counting the cpu
+ * directories in "/sys/devices/system/cpu" and fallback on the value from
+ * sysconf if it fails.
+ */
+
+#include <dirent.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#define __max(a,b) ((a)>(b)?(a):(b))
+
+void _get_num_possible_cpus(void)
+{
+       int result, count = 0;
+       DIR *cpudir;
+       struct dirent *entry;
+
+       cpudir = opendir("/sys/devices/system/cpu");
+       if (cpudir == NULL)
+               goto end;
+
+       /*
+        * Count the number of directories named "cpu" followed by and
+        * integer. This is the same strategy as glibc uses.
+        */
+       while ((entry = readdir(cpudir))) {
+               if (entry->d_type == DT_DIR &&
+                       strncmp(entry->d_name, "cpu", 3) == 0) {
+
+                       char *endptr;
+                       unsigned long cpu_num;
+
+                       cpu_num = strtoul(entry->d_name + 3, &endptr, 10);
+                       if ((cpu_num < ULONG_MAX) && (endptr != entry->d_name + 3)
+                                       && (*endptr == '\0')) {
+                               count++;
+                       }
+               }
+       }
+
+end:
+       /*
+        * Get the sysconf value as a fallback. Keep the highest number.
+        */
+       result = __max(sysconf(_SC_NPROCESSORS_CONF), count);
+
+       /*
+        * If both methods failed, don't store the value.
+        */
+       if (result < 1)
+               return;
+       __num_possible_cpus = result;
+}
+#endif