Deactivate when blocked on load phase mutex

This turned out to be important when building in multiple contexts that share
the scheduler (e.g., main and module/recipe build context). In this case we
need an accurate active thread count in order to decide when to start an extra
helper thread past max_active.

1 files changed, 12 insertions, 2 deletions

diff --git a/libbuild2/context.cxx b/libbuild2/context.cxx
index 09ab15d..b4ba5df 100644
--- a/libbuild2/context.cxx
+++ b/libbuild2/context.cxx
@@ -664,7 +664,12 @@ namespace build2
     //
     if (p == run_phase::load)
     {
-      lm_.lock ();
+      if (!lm_.try_lock ())
+      {
+        ctx_.sched.deactivate (false /* external */);
+        lm_.lock ();
+        ctx_.sched.activate (false /* external */);
+      }
       r = !fail_; // Re-query.
     }
 
@@ -773,7 +778,12 @@ namespace build2
 
     if (n == run_phase::load)
     {
-      lm_.lock ();
+      if (!lm_.try_lock ())
+      {
+        ctx_.sched.deactivate (false /* external */);
+        lm_.lock ();
+        ctx_.sched.activate (false /* external */);
+      }
       r = !fail_; // Re-query.
     }