fixup! threads: avoid deadlock from recursive lock acquire

src/task.c

@@ -510,11 +510,13 @@ JL_DLLEXPORT void jl_switch(void)
         jl_error("cannot switch to task running on another thread");
     }
 
-    // Store old values on the stack
+    // Store old values on the stack and reset
     sig_atomic_t defer_signal = ptls->defer_signal;
     int8_t gc_state = jl_gc_unsafe_enter(ptls);
     size_t world_age = ptls->world_age;
     int finalizers_inhibited = ptls->finalizers_inhibited;
+    ptls->world_age = 0;
+    ptls->finalizers_inhibited = 0;
 
 #ifdef ENABLE_TIMINGS
     jl_timing_block_t *blk = ptls->timing_stack;
@@ -538,7 +540,9 @@ JL_DLLEXPORT void jl_switch(void)
 #endif
 
     // Pop old values back off the stack
-    assert(ct == ptls->current_task);
+    assert(ct == ptls->current_task &&
+           0 == ptls->world_age &&
+           0 == ptls->finalizers_inhibited);
     ptls->world_age = world_age;
     ptls->finalizers_inhibited = finalizers_inhibited;
 
@@ -801,6 +805,7 @@ STATIC_OR_JS void NOINLINE JL_NORETURN start_task(void)
     jl_ptls_t ptls = jl_get_ptls_states();
     jl_task_t *t = ptls->current_task;
     jl_value_t *res;
+    assert(ptls->finalizers_inhibited == 0);
 
 #ifdef MIGRATE_TASKS
     jl_task_t *pt = ptls->previous_task;