Changeset becb85b9 for libcfa/src/concurrency

Timestamp:

Feb 4, 2022, 2:44:10 PM (2 years ago)

Author:

Thierry Delisle <tdelisle@…>

Branches:

ADT, ast-experimental, enum, forall-pointer-decay, master, pthread-emulation, qualifiedEnum

Children:

67e86ae6

Parents:

941e14a

Message:

Attempt to fix preemption deadlock.
No longer prevent preemption during cfaabi_check_preemption.
preemption_enabled() now does a roll forward if it blocked a preemption.

File:

• libcfa/src/concurrency/preemption.cfa (modified) (6 diffs)

libcfa/src/concurrency/preemption.cfa

@@ -251 +251 @@
         bool enabled = __cfaabi_tls.preemption_state.enabled;
 
+        // Check if there is a pending preemption
+        processor   * proc = __cfaabi_tls.this_processor;
+        bool pending = proc ? proc->pending_preemption : false;
+        if( enabled && pending ) proc->pending_preemption = false;
+
         // create a assembler label after
         // marked as clobber all to avoid movement
         __cfaasm_label(check, after);
+
+        // If we can preempt and there is a pending one
+        // this is a good time to yield
+        if( enabled && pending ) {
+                force_yield( __POLL_PREEMPTION );
+        }
         return enabled;
 }
@@ -282 +293 @@
         // marked as clobber all to avoid movement
         __cfaasm_label(get, after);
+
+        // This is used everywhere, to avoid cost, we DO NOT poll pending preemption
         return val;
 }
@@ -358 +371 @@
         if(!ready) { abort("Preemption should be ready"); }
 
-        __cfaasm_label(debug, before);
+        // __cfaasm_label(debug, before);
 
                 sigset_t oldset;
@@ -377 +390 @@
                 if(ret == 1) { abort("ERROR SIGTERM is disabled"); }
 
-        __cfaasm_label(debug, after);
+        // __cfaasm_label(debug, after);
 }
 
@@ -548 +561 @@
         __cfaasm_label( check  );
         __cfaasm_label( dsable );
-        __cfaasm_label( debug  );
+        // __cfaasm_label( debug  );
 
         // Check if preemption is safe
@@ -555 +568 @@
         if( __cfaasm_in( ip, check  ) ) { ready = false; goto EXIT; };
         if( __cfaasm_in( ip, dsable ) ) { ready = false; goto EXIT; };
-        if( __cfaasm_in( ip, debug  ) ) { ready = false; goto EXIT; };
+        // if( __cfaasm_in( ip, debug  ) ) { ready = false; goto EXIT; };
         if( !__cfaabi_tls.preemption_state.enabled) { ready = false; goto EXIT; };
         if( __cfaabi_tls.preemption_state.in_progress ) { ready = false; goto EXIT; };