Fix: race between lttng-ust getenv() and application setenv()

[lttng-ust.git] / liblttng-ust / lttng-ust-statedump.c

diff --git a/liblttng-ust/lttng-ust-statedump.c b/liblttng-ust/lttng-ust-statedump.c
index 2fb8f34d9b4f4e34d803813498187273441fc487..efa8a55aa675771c50ac57031c985f1787c70e21 100644 (file)
--- a/liblttng-ust/lttng-ust-statedump.c
+++ b/liblttng-ust/lttng-ust-statedump.c
@@ -34,6 +34,7 @@
 #include "lttng-tracer-core.h"
 #include "lttng-ust-statedump.h"
 #include "jhash.h"
+#include "getenv.h"
 
 #define TRACEPOINT_DEFINE
 #include "ust_lib.h"                           /* Only define. */
@@ -548,9 +549,15 @@ void lttng_ust_dl_update(void *ip)
 {
        struct dl_iterate_data data;
 
-       if (getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
+       if (lttng_getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
                return;
 
+       /*
+        * Fixup lttng-ust TLS when called from dlopen/dlclose
+        * instrumentation.
+        */
+       lttng_ust_fixup_tls();
+
        data.exec_found = 0;
        data.first = true;
        data.cancel = false;
@@ -576,7 +583,7 @@ void lttng_ust_dl_update(void *ip)
 static
 int do_baddr_statedump(void *owner)
 {
-       if (getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
+       if (lttng_getenv("LTTNG_UST_WITHOUT_BADDR_STATEDUMP"))
                return 0;
        lttng_ust_dl_update(LTTNG_UST_CALLER_IP());
        ust_dl_table_statedump(owner);
@@ -590,12 +597,22 @@ int do_baddr_statedump(void *owner)
  * session, statedumps from different processes may be
  * interleaved. The vpid context should be used to identify which
  * events belong to which process.
+ *
+ * Grab the ust_lock outside of the RCU read-side lock because we
+ * perform synchronize_rcu with the ust_lock held, which can trigger
+ * deadlocks otherwise.
  */
 int do_lttng_ust_statedump(void *owner)
 {
+       ust_lock_nocheck();
        trace_statedump_start(owner);
+       ust_unlock();
+
        do_baddr_statedump(owner);
+
+       ust_lock_nocheck();
        trace_statedump_end(owner);
+       ust_unlock();
 
        return 0;
 }