X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fcommon%2Fgetenv.c;h=120225e6bc888104262856849ea9a51fcb71151d;hb=HEAD;hp=1909f4cf912bd8f80ebf51e6fc5dd88bb866607c;hpb=910dcd720731c190adbfb9bb50c67bb9c4235003;p=lttng-ust.git

diff --git a/src/common/getenv.c b/src/common/getenv.c
index 1909f4cf..120225e6 100644
--- a/src/common/getenv.c
+++ b/src/common/getenv.c
@@ -9,6 +9,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <sys/types.h>
+#include <pthread.h>
 #include <urcu/system.h>
 #include "common/logging.h"
 #include "common/macros.h"
@@ -25,20 +26,23 @@ struct lttng_env {
 	char *value;
 };
 
-static
-int lttng_ust_getenv_is_init = 0;
+/* lttng_ust_getenv_init_mutex provides mutual exclusion for initialization. */
+static pthread_mutex_t lttng_ust_getenv_init_mutex = PTHREAD_MUTEX_INITIALIZER;
+static int lttng_ust_getenv_is_init = 0;
 
 static struct lttng_env lttng_env[] = {
 	/*
-	 * LTTNG_UST_DEBUG is used directly by snprintf, because it
-	 * needs to be already set for ERR() used in
-	 * lttng_ust_getenv_init().
+	 * LTTNG_UST_DEBUG and LTTNG_UST_ABORT_ON_CRITICAL are used directly by
+	 * the internal logging, because they need to be already set for ERR()
+	 * used in lttng_ust_getenv_init().
 	 */
 	{ "LTTNG_UST_DEBUG", LTTNG_ENV_NOT_SECURE, NULL, },
+	{ "LTTNG_UST_ABORT_ON_CRITICAL", LTTNG_ENV_NOT_SECURE, NULL, },
 
 	/* Env. var. which can be used in setuid/setgid executables. */
 	{ "LTTNG_UST_WITHOUT_BADDR_STATEDUMP", LTTNG_ENV_NOT_SECURE, NULL, },
 	{ "LTTNG_UST_REGISTER_TIMEOUT", LTTNG_ENV_NOT_SECURE, NULL, },
+	{ "LTTNG_UST_MAP_POPULATE_POLICY", LTTNG_ENV_NOT_SECURE, NULL, },
 
 	/* Env. var. which are not fetched in setuid/setgid executables. */
 	{ "LTTNG_UST_CLOCK_PLUGIN", LTTNG_ENV_SECURE, NULL, },
@@ -46,6 +50,7 @@ static struct lttng_env lttng_env[] = {
 	{ "LTTNG_UST_ALLOW_BLOCKING", LTTNG_ENV_SECURE, NULL, },
 	{ "HOME", LTTNG_ENV_SECURE, NULL, },
 	{ "LTTNG_HOME", LTTNG_ENV_SECURE, NULL, },
+	{ "LTTNG_UST_APP_PATH", LTTNG_ENV_SECURE, NULL, },
 };
 
 static
@@ -64,8 +69,11 @@ char *lttng_ust_getenv(const char *name)
 	struct lttng_env *e;
 	bool found = false;
 
-	if (!CMM_LOAD_SHARED(lttng_ust_getenv_is_init))
-		abort();
+	/*
+	 * Perform lazy initialization of lttng_ust_getenv for early use
+	 * by library constructors.
+	 */
+	lttng_ust_getenv_init();
 
 	for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
 		e = &lttng_env[i];
@@ -85,8 +93,25 @@ void lttng_ust_getenv_init(void)
 {
 	size_t i;
 
-	if (CMM_LOAD_SHARED(lttng_ust_getenv_is_init))
+	/*
+	 * Return early if the init has already completed.
+	 */
+	if (CMM_LOAD_SHARED(lttng_ust_getenv_is_init)) {
+		/*
+		 * Load lttng_ust_getenv_is_init before reading environment cache.
+		 */
+		cmm_smp_rmb();
 		return;
+	}
+
+	pthread_mutex_lock(&lttng_ust_getenv_init_mutex);
+
+	/*
+	 * Check again if the init has completed in another thread now that we
+	 * have acquired the mutex.
+	 */
+	if (lttng_ust_getenv_is_init)
+		goto end_init;
 
 	for (i = 0; i < LTTNG_ARRAY_SIZE(lttng_env); i++) {
 		struct lttng_env *e = &lttng_env[i];
@@ -98,5 +123,12 @@ void lttng_ust_getenv_init(void)
 		}
 		e->value = getenv(e->key);
 	}
+
+	/*
+	 * Store environment cache before setting lttng_ust_getenv_is_init to 1.
+	 */
+	cmm_smp_wmb();
 	CMM_STORE_SHARED(lttng_ust_getenv_is_init, 1);
+end_init:
+	pthread_mutex_unlock(&lttng_ust_getenv_init_mutex);
 }