Revert "fix a race in jobsystem"

This reverts commit 2feb0ad325.

libs/utils/src/JobSystem.cpp

@@ -323,6 +323,11 @@ bool JobSystem::execute(JobSystem::ThreadState& state) noexcept {
     if (job) {
         assert(job->runningJobCount.load(std::memory_order_relaxed) >= 1);
 
+        UTILS_UNUSED_IN_RELEASE
+        uint32_t activeJobs = mActiveJobs.fetch_sub(1, std::memory_order_relaxed);
+        assert(activeJobs); // whoops, we were already at 0
+        HEAVY_SYSTRACE_VALUE32("JobSystem::activeJobs", activeJobs - 1);
+
         if (UTILS_LIKELY(job->function)) {
             HEAVY_SYSTRACE_NAME("job->function");
             job->function(job->storage, *this, job);
@@ -441,8 +446,18 @@ void JobSystem::run(Job*& job) noexcept {
 
     ThreadState& state(getState());
 
+    // increase the active job count before we add the job to the queue, because otherwise
+    // the job could run and finish before the counter is incremented, which would trigger
+    // an assert() in execute(). Either way, it's not "wrong", but the assert() is useful.
+    uint32_t activeJobs = mActiveJobs.fetch_add(1, std::memory_order_relaxed);
+
     put(state.workQueue, job);
 
+    HEAVY_SYSTRACE_VALUE32("JobSystem::activeJobs", activeJobs + 1);
+
+    // wake-up a thread if needed...
+    wakeOne();
+
     // after run() returns, the job is virtually invalid (it'll die on its own)
     job = nullptr;
 }