Fix race condition in update_stat()

diff --git a/src/linux.c b/src/linux.c
index 12b0104..daaeb73 100644 (file)
--- a/src/linux.c
+++ b/src/linux.c
@@ -63,6 +63,7 @@
 #endif
 #include <linux/route.h>
 #include <math.h>
+#include <pthread.h>
 
 /* The following ifdefs were adapted from gkrellm */
 #include <linux/major.h>
@@ -672,14 +673,20 @@ void update_stat(void)
        const char *stat_template = NULL;
        unsigned int malloc_cpu_size = 0;
        extern void* global_cpu;
+
+       static pthread_mutex_t last_stat_update_mutex = PTHREAD_MUTEX_INITIALIZER;
        static double last_stat_update = 0.0;
 
        /* since we use wrappers for this function, the update machinery
         * can't eliminate double invocations of this function. Check for
         * them here, otherwise cpu_usage counters are freaking out. */
-       if (last_stat_update == current_update_time)
+       pthread_mutex_lock(&last_stat_update_mutex);
+       if (last_stat_update == current_update_time) {
+               pthread_mutex_unlock(&last_stat_update_mutex);
                return;
+       }
        last_stat_update = current_update_time;
+       pthread_mutex_unlock(&last_stat_update_mutex);
 
        /* add check for !info.cpu_usage since that mem is freed on a SIGUSR1 */
        if (!cpu_setup || !info.cpu_usage) {