erts: Fix locking order violation for allocation wrappers

Some query functions in erl_alloc_util.c lock the allocator mutex
and then use erts_printf that in turn may call the sys allocator
through the wrappers. To avoid breaking locking order these
query functions first "pre-locks" all allocator wrappers.

1 files changed, 51 insertions, 0 deletions

diff --git a/erts/emulator/beam/erl_alloc.c b/erts/emulator/beam/erl_alloc.c
index f0cc52e30f..c19a2647e4 100644
--- a/erts/emulator/beam/erl_alloc.c
+++ b/erts/emulator/beam/erl_alloc.c
@@ -570,6 +570,8 @@ erts_alloc_init(int *argc, char **argv, ErtsAllocInitOpts *eaiop)
     if (ncpu < 1)
 	ncpu = 1;
 
+    erts_tsd_key_create(&erts_allctr_prelock_tsd_key);
+
     erts_sys_alloc_init();
     erts_init_utils_mem();
 
@@ -3139,6 +3141,55 @@ erts_request_alloc_info(struct process *c_p,
     return 1;
 }
 
+/* 
+ * The allocator wrapper prelocking stuff below is about the locking order.
+ * It only affects wrappers (erl_mtrace.c and erl_instrument.c) that keep locks
+ * during alloc/realloc/free.
+ *
+ * Some query functions in erl_alloc_util.c lock the allocator mutex and then
+ * use erts_printf that in turn may call the sys allocator through the wrappers.
+ * To avoid breaking locking order these query functions first "pre-locks" all
+ * allocator wrappers.
+ */
+ErtsAllocatorWrapper_t *erts_allctr_wrappers;
+int erts_allctr_wrapper_prelocked = 0;
+erts_tsd_key_t erts_allctr_prelock_tsd_key;
+
+void erts_allctr_wrapper_prelock_init(ErtsAllocatorWrapper_t* wrapper)
+{
+    ASSERT(wrapper->lock && wrapper->unlock);
+    wrapper->next = erts_allctr_wrappers;
+    erts_allctr_wrappers = wrapper;
+}
+
+void erts_allctr_wrapper_pre_lock(void)
+{
+    if (erts_allctr_wrappers) {
+	ErtsAllocatorWrapper_t* wrapper = erts_allctr_wrappers;
+	for ( ; wrapper; wrapper = wrapper->next) {
+	    wrapper->lock();
+	}
+	ASSERT(!erts_allctr_wrapper_prelocked);
+	erts_allctr_wrapper_prelocked = 1;
+	erts_tsd_set(erts_allctr_prelock_tsd_key, (void*)1);
+    }
+}
+
+void erts_allctr_wrapper_pre_unlock(void)
+{
+    if (erts_allctr_wrappers) {
+	ErtsAllocatorWrapper_t* wrapper = erts_allctr_wrappers;
+	
+	erts_allctr_wrapper_prelocked = 0;
+	erts_tsd_set(erts_allctr_prelock_tsd_key, (void*)0);
+	for ( ; wrapper; wrapper = wrapper->next) {
+	    wrapper->unlock();
+	}
+    }
+}
+
+
+
 /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
  * Deprecated functions                                                    *
  *                                                                         *