diff options
Diffstat (limited to 'libbuild2/scheduler.cxx')
| -rw-r--r-- | libbuild2/scheduler.cxx | 31 |
1 files changed, 23 insertions, 8 deletions
diff --git a/libbuild2/scheduler.cxx b/libbuild2/scheduler.cxx index bdd703d..469ded7 100644 --- a/libbuild2/scheduler.cxx +++ b/libbuild2/scheduler.cxx @@ -362,8 +362,14 @@ namespace build2 size_t init_active, size_t max_threads, size_t queue_depth, - optional<size_t> max_stack) + optional<size_t> max_stack, + size_t orig_max_active) { + if (orig_max_active == 0) + orig_max_active = max_active; + else + assert (max_active <= orig_max_active); + // Lock the mutex to make sure our changes are visible in (other) active // threads. // @@ -375,16 +381,18 @@ namespace build2 // were asked to run serially. // if (max_threads == 0) - max_threads = (max_active == 1 ? 1 : - sizeof (void*) < 8 ? 8 : 32) * max_active; + max_threads = (orig_max_active == 1 + ? 1 + : (sizeof (void*) < 8 ? 8 : 32) * orig_max_active); assert (shutdown_ && init_active != 0 && init_active <= max_active && - max_active <= max_threads); + orig_max_active <= max_threads); active_ = init_active_ = init_active; - max_active_ = orig_max_active_ = max_active; + max_active_ = max_active; + orig_max_active_ = orig_max_active; max_threads_ = max_threads; // This value should be proportional to the amount of hardware concurrency @@ -398,7 +406,7 @@ namespace build2 // task_queue_depth_ = queue_depth != 0 ? queue_depth - : max_active * 8; + : orig_max_active_ * 8; queued_task_count_.store (0, memory_order_relaxed); @@ -421,6 +429,8 @@ namespace build2 shutdown_ = false; + // Delay thread startup if serial. + // if (max_active_ != 1) dead_thread_ = thread (deadlock_monitor, this); } @@ -429,7 +439,7 @@ namespace build2 tune (size_t max_active) { // Note that if we tune a parallel scheduler to run serially, we will - // still have the deadlock monitoring thread running. + // still have the deadlock monitoring thread loitering around. // With multiple initial active threads we will need to make changes to // max_active_ visible to other threads and which we currently say can be @@ -451,6 +461,11 @@ namespace build2 lock l (wait_idle ()); swap (max_active_, max_active); + + // Start the deadlock thread if its startup was delayed. + // + if (max_active_ != 1 && !dead_thread_.joinable ()) + dead_thread_ = thread (deadlock_monitor, this); } return max_active == orig_max_active_ ? 0 : max_active; @@ -519,7 +534,7 @@ namespace build2 // Wait for the deadlock monitor (the only remaining thread). // - if (orig_max_active_ != 1) // See tune() for why not max_active_. + if (dead_thread_.joinable ()) { l.unlock (); dead_condv_.notify_one (); |