Merge pull request #32114 from JuliaLang/jb/toomanytasks

avoid error when Task multiq is full

Author: JeffBezanson

base/task.jl

@@ -419,7 +419,12 @@ function enq_work(t::Task)
         push!(Workqueues[tid], t)
     else
         tid = 0
-        ccall(:jl_enqueue_task, Cvoid, (Any,), t)
+        if ccall(:jl_enqueue_task, Cint, (Any,), t) != 0
+            # if multiq is full, give to a random thread (TODO fix)
+            tid = mod(time_ns() % Int, Threads.nthreads()) + 1
+            ccall(:jl_set_task_tid, Cvoid, (Any, Cint), t, tid-1)
+            push!(Workqueues[tid], t)
+        end
     end
     ccall(:jl_wakeup_thread, Cvoid, (Int16,), (tid - 1) % Int16)
     return t

src/partr.c

@@ -46,10 +46,10 @@ typedef struct taskheap_tag {
 
 /* multiqueue parameters */
 static const int16_t heap_d = 8;
-static const int heap_c = 4;
+static const int heap_c = 16;
 
 /* size of each heap */
-static const int tasks_per_heap = 8192; // TODO: this should be smaller by default, but growable!
+static const int tasks_per_heap = 16384; // TODO: this should be smaller by default, but growable!
 
 /* the multiqueue's heaps */
 static taskheap_t *heaps;
@@ -117,7 +117,7 @@ static inline int multiq_insert(jl_task_t *task, int16_t priority)
 
     if (heaps[rn].ntasks >= tasks_per_heap) {
         jl_mutex_unlock_nogc(&heaps[rn].lock);
-        jl_error("multiq insertion failed, increase #tasks per heap");
+        // multiq insertion failed, increase #tasks per heap
         return -1;
     }
 
@@ -287,9 +287,11 @@ void jl_threadfun(void *arg)
 
 
 // enqueue the specified task for execution
-JL_DLLEXPORT void jl_enqueue_task(jl_task_t *task)
+JL_DLLEXPORT int jl_enqueue_task(jl_task_t *task)
 {
-    multiq_insert(task, task->prio);
+    if (multiq_insert(task, task->prio) == -1)
+        return 1;
+    return 0;
 }
 
 
@@ -372,17 +374,22 @@ JL_DLLEXPORT void jl_wakeup_thread(int16_t tid)
 }
 
 
+JL_DLLEXPORT void jl_set_task_tid(jl_task_t *task, int tid)
+{
+    // Try to acquire the lock on this task.
+    // If this fails, we'll check for that error later (in jl_switchto).
+    if (jl_atomic_load_acquire(&task->tid) != tid) {
+        jl_atomic_compare_exchange(&task->tid, -1, tid);
+    }
+}
+
 // get the next runnable task from the multiq
 static jl_task_t *get_next_task(jl_value_t *getsticky)
 {
     jl_task_t *task = (jl_task_t*)jl_apply(&getsticky, 1);
     if (jl_typeis(task, jl_task_type)) {
         int self = jl_get_ptls_states()->tid;
-        // try to acquire the lock on this task now
-        // we'll check this error later (in yieldto)
-        if (jl_atomic_load_acquire(&task->tid) != self) {
-            jl_atomic_compare_exchange(&task->tid, -1, self);
-        }
+        jl_set_task_tid(task, self);
         return task;
     }
 #ifdef JULIA_ENABLE_THREADING

src/task.c

@@ -151,14 +151,14 @@ void JL_NORETURN jl_finish_task(jl_task_t *t, jl_value_t *resultval JL_MAYBE_UNR
 {
     jl_ptls_t ptls = jl_get_ptls_states();
     JL_SIGATOMIC_BEGIN();
+    t->result = resultval;
+    jl_gc_wb(t, t->result);
     if (t->exception != jl_nothing)
-        t->state = failed_sym;
+        jl_atomic_store_release(&t->state, failed_sym);
     else
-        t->state = done_sym;
+        jl_atomic_store_release(&t->state, done_sym);
     if (t->copy_stack) // early free of stkbuf
         t->stkbuf = NULL;
-    t->result = resultval;
-    jl_gc_wb(t, t->result);
     // ensure that state is cleared
     ptls->in_finalizer = 0;
     ptls->in_pure_callback = 0;