MINOR: task/debug: explicitly support passing a null caller to wakeup functions

This is used for tracing and profiling. By permitting to have a NULL
caller, we allow a caller to explicitly pass zero to state that the
current caller must not be replaced. This will soon be used by
wake_expired_tasks() to avoid replacing a caller in the expire loop.

diff --git a/include/haproxy/task.h b/include/haproxy/task.h
index 1f544be1704e15343fa6c86f3bb88816f46eb294..592d9c1e5082a805373d40e6e0c9d01bf424c371 100644 (file)
--- a/include/haproxy/task.h
+++ b/include/haproxy/task.h
@@ -209,11 +209,13 @@ static inline void _task_wakeup(struct task *t, unsigned int f, const struct ha_
        state = _HA_ATOMIC_OR_FETCH(&t->state, f);
        while (!(state & (TASK_RUNNING | TASK_QUEUED))) {
                if (_HA_ATOMIC_CAS(&t->state, &state, state | TASK_QUEUED)) {
-                       caller = HA_ATOMIC_XCHG(&t->caller, caller);
-                       BUG_ON((ulong)caller & 1);
+                       if (likely(caller)) {
+                               caller = HA_ATOMIC_XCHG(&t->caller, caller);
+                               BUG_ON((ulong)caller & 1);
 #ifdef DEBUG_TASK
-                       HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
+                               HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
 #endif
+                       }
                        __task_wakeup(t);
                        break;
                }
@@ -247,11 +249,13 @@ static inline void _task_drop_running(struct task *t, unsigned int f, const stru
        }
 
        if ((new_state & ~state) & TASK_QUEUED) {
-               caller = HA_ATOMIC_XCHG(&t->caller, caller);
-               BUG_ON((ulong)caller & 1);
+               if (likely(caller)) {
+                       caller = HA_ATOMIC_XCHG(&t->caller, caller);
+                       BUG_ON((ulong)caller & 1);
 #ifdef DEBUG_TASK
-               HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
+                       HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
 #endif
+               }
                __task_wakeup(t);
        }
 }
@@ -370,11 +374,14 @@ static inline void _tasklet_wakeup_on(struct tasklet *tl, int thr, const struct
        } while (!_HA_ATOMIC_CAS(&tl->state, &state, state | TASK_IN_LIST));
 
        /* at this point we're the first ones to add this task to the list */
-       caller = HA_ATOMIC_XCHG(&tl->caller, caller);
-       BUG_ON((ulong)caller & 1);
+       if (likely(caller)) {
+               caller = HA_ATOMIC_XCHG(&tl->caller, caller);
+               BUG_ON((ulong)caller & 1);
 #ifdef DEBUG_TASK
-       HA_ATOMIC_STORE(&tl->debug.prev_caller, caller);
+               HA_ATOMIC_STORE(&tl->debug.prev_caller, caller);
 #endif
+       }
+
        if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_TASK_PROFILING)
                tl->wake_date = now_mono_time();
        __tasklet_wakeup_on(tl, thr);
@@ -424,11 +431,14 @@ static inline void _task_instant_wakeup(struct task *t, unsigned int f, const st
        BUG_ON_HOT(task_in_rq(t));
 
        /* at this point we're the first ones to add this task to the list */
-       caller = HA_ATOMIC_XCHG(&t->caller, caller);
-       BUG_ON((ulong)caller & 1);
+       if (likely(caller)) {
+               caller = HA_ATOMIC_XCHG(&t->caller, caller);
+               BUG_ON((ulong)caller & 1);
 #ifdef DEBUG_TASK
-       HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
+               HA_ATOMIC_STORE(&t->debug.prev_caller, caller);
 #endif
+       }
+
        if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_TASK_PROFILING)
                t->wake_date = now_mono_time();
        __tasklet_wakeup_on((struct tasklet *)t, thr);
@@ -458,11 +468,14 @@ static inline struct list *_tasklet_wakeup_after(struct list *head, struct taskl
        } while (!_HA_ATOMIC_CAS(&tl->state, &state, state | TASK_IN_LIST));
 
        /* at this point we're the first one to add this task to the list */
-       caller = HA_ATOMIC_XCHG(&tl->caller, caller);
-       BUG_ON((ulong)caller & 1);
+       if (likely(caller)) {
+               caller = HA_ATOMIC_XCHG(&tl->caller, caller);
+               BUG_ON((ulong)caller & 1);
 #ifdef DEBUG_TASK
-       HA_ATOMIC_STORE(&tl->debug.prev_caller, caller);
+               HA_ATOMIC_STORE(&tl->debug.prev_caller, caller);
 #endif
+       }
+
        if (th_ctx->flags & TH_FL_TASK_PROFILING)
                tl->wake_date = now_mono_time();
        return __tasklet_wakeup_after(head, tl);