fix: removed accidental VLA in _get_num_possible_cpus()

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

diff --git a/libringbuffer/smp.h b/libringbuffer/smp.h
index 034058e9ee54ea032420fa8153636071f83cf3cf..0db9e8418852129eeddea55c87bb24f644023638 100644 (file)
--- a/libringbuffer/smp.h
+++ b/libringbuffer/smp.h
@@ -4,9 +4,21 @@
 /*
  * libringbuffer/smp.h
  *
- * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * 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
  */
 
 #include "getcpu.h"
@@ -18,13 +30,55 @@
 #define PER_CPU_MEM_SIZE       4096
 
 extern int __num_possible_cpus;
+
+#define LTTNG_UST_CPUMASK_SIZE 4096
+
+/*
+ * Get the CPU possible mask string from sysfs.
+ *
+ * buf: the buffer where the mask will be read.
+ * max_bytes: the maximum number of bytes to write in the buffer.
+ *
+ * Returns the number of bytes read or -1 on error.
+ */
+int get_possible_cpu_mask_from_sysfs(char *buf, size_t max_bytes)
+       __attribute__((visibility("hidden")));
+
+/*
+ * Get the number of possible CPUs in the system from either
+ * sysconf(_SC_NPROCESSORS_CONF) or some other mechanism depending on the libc.
+ *
+ * Returns the number of possible CPUs in the system or 0 on error.
+ */
+int get_num_possible_cpus_fallback(void)
+       __attribute__((visibility("hidden")));
+
+/*
+ * Get the number of CPUs from the possible 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.
+ */
+int get_num_possible_cpus_from_mask(const char *pmask, size_t len)
+       __attribute__((visibility("hidden")));
+
 extern void _get_num_possible_cpus(void);
 
+/*
+ * 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.
+ *
+ * If all methods fail, don't populate the cache and return 0.
+ */
 static inline
 int num_possible_cpus(void)
 {
-       if (!__num_possible_cpus)
+       if (caa_unlikely(!__num_possible_cpus))
                _get_num_possible_cpus();
+
        return __num_possible_cpus;
 }