rt: Don't kill tasks while they are in a callback from C

Author: brson

Diff for: src/rt/rust_builtin.cpp

@@ -576,7 +576,7 @@ port_recv(uintptr_t *dptr, rust_port *port,
 
         // If this task has been killed then we're not going to bother
         // blocking, we have to unwind.
-        if (task->killed) {
+        if (task->must_fail_from_being_killed()) {
             *killed = true;
             return;
         }

Diff for: src/rt/rust_task.cpp

@@ -84,11 +84,12 @@ rust_task::rust_task(rust_task_thread *thread, rust_task_list *state,
     local_region(&thread->srv->local_region),
     boxed(&local_region),
     unwinding(false),
-    killed(false),
     propagate_failure(true),
     dynastack(this),
     cc_counter(0),
     total_stack_sz(0),
+    killed(false),
+    reentered_rust_stack(false),
     c_stack(NULL),
     next_c_sp(0),
     next_rust_sp(0)
@@ -240,17 +241,22 @@ void rust_task::start()
     transition(&thread->newborn_tasks, &thread->running_tasks);
 }
 
+bool
+rust_task::must_fail_from_being_killed() {
+    return killed && !reentered_rust_stack;
+}
+
 // Only run this on the rust stack
 void
 rust_task::yield(bool *killed) {
-    if (this->killed) {
+    if (must_fail_from_being_killed()) {
         *killed = true;
     }
 
     // Return to the scheduler.
     ctx.next->swap(ctx);
 
-    if (this->killed) {
+    if (must_fail_from_being_killed()) {
         *killed = true;
     }
 }

Diff for: src/rt/rust_task.h

@@ -37,6 +37,7 @@ typedef unsigned long task_result;
 #define tr_failure 1
 
 struct spawn_args;
+struct cleanup_args;
 
 // std::lib::task::task_notification
 //
@@ -88,8 +89,6 @@ rust_task : public kernel_owned<rust_task>, rust_cond
     // We use this to suppress the "killed" flag during calls to yield.
     bool unwinding;
 
-    // Indicates that the task was killed and needs to unwind
-    bool killed;
     bool propagate_failure;
 
     lock_and_signal lock;
@@ -107,6 +106,11 @@ rust_task : public kernel_owned<rust_task>, rust_cond
 
 private:
 
+    // Indicates that the task was killed and needs to unwind
+    bool killed;
+    // Indicates that we've called back into Rust from C
+    bool reentered_rust_stack;
+
     // The stack used for running C code, borrowed from the scheduler thread
     stk_seg *c_stack;
     uintptr_t next_c_sp;
@@ -123,6 +127,7 @@ rust_task : public kernel_owned<rust_task>, rust_cond
     void return_c_stack();
 
     friend void task_start_wrapper(spawn_args *a);
+    friend void cleanup_task(cleanup_args *a);
 
 public:
 
@@ -162,6 +167,10 @@ rust_task : public kernel_owned<rust_task>, rust_cond
     // Fail this task (assuming caller-on-stack is different task).
     void kill();
 
+    // Indicates that we've been killed and now is an apropriate
+    // time to fail as a result
+    bool must_fail_from_being_killed();
+
     // Fail self, assuming caller-on-stack is this task.
     void fail();
     void conclude_failure();
@@ -262,6 +271,9 @@ rust_task::call_on_rust_stack(void *args, void *fn_ptr) {
     // I(thread, !on_rust_stack());
     I(thread, next_rust_sp);
 
+    bool had_reentered_rust_stack = reentered_rust_stack;
+    reentered_rust_stack = true;
+
     uintptr_t prev_c_sp = next_c_sp;
     next_c_sp = get_sp();
 
@@ -270,6 +282,7 @@ rust_task::call_on_rust_stack(void *args, void *fn_ptr) {
     __morestack(args, fn_ptr, sp);
 
     next_c_sp = prev_c_sp;
+    reentered_rust_stack = had_reentered_rust_stack;
 }
 
 inline void

Diff for: src/test/run-fail/crust-fail.rs

@@ -0,0 +1,31 @@
+// error-pattern:explicit failure
+// Testing that runtime failure doesn't cause callbacks to abort abnormally.
+// Instead the failure will be delivered after the callbacks return.
+
+native mod rustrt {
+    fn rust_dbg_call(cb: *u8,
+                     data: ctypes::uintptr_t) -> ctypes::uintptr_t;
+}
+
+crust fn cb(data: ctypes::uintptr_t) -> ctypes::uintptr_t {
+    if data == 1u {
+        data
+    } else {
+        count(data - 1u) + count(data - 1u)
+    }
+}
+
+fn count(n: uint) -> uint {
+    task::yield();
+    rustrt::rust_dbg_call(cb, n)
+}
+
+fn main() {
+    iter::repeat(10u) {||
+        task::spawn {||
+            let result = count(5u);
+            #debug("result = %?", result);
+            fail;
+        };
+    }
+}