X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=libringbuffer%2Fsmp.c;h=39bd5559094e75b6305e96f13e8002312f7861c5;hb=f574bfb4d81b26d3cfc0243868d138e33470a950;hp=ffc7a52a180a42af05270979e222b2558a6c288c;hpb=eb2b066ff35dcafa727fae7e8853a9750233063e;p=lttng-ust.git

diff --git a/libringbuffer/smp.c b/libringbuffer/smp.c
index ffc7a52a..39bd5559 100644
--- a/libringbuffer/smp.c
+++ b/libringbuffer/smp.c
@@ -1,30 +1,18 @@
 /*
- * 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>
 #include "smp.h"
 
 int __num_possible_cpus;
 
+#if (defined(__GLIBC__) || defined( __UCLIBC__))
 void _get_num_possible_cpus(void)
 {
 	int result;
@@ -42,3 +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