X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=c4e354e4b73d6bf15de78d610aadec8fb17e9fc2;hp=4864b1cb151f70e2e1fc1849e198c9abc24802a6;hb=dafd5b58642e70c3746fc90e467c35465eb65a00;hpb=eabba1119f45f2ac8a3a6248bd1c1d9868d7af5c

diff --git a/src/search.cpp b/src/search.cpp
index 4864b1cb..c4e354e4 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -409,7 +409,8 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
   read_evaluation_uci_options(pos.side_to_move());
   Threads.read_uci_options();
 
-  // If needed allocate pawn and material hash tables and adjust TT size
+  // Allocate pawn and material hash tables if number of active threads
+  // increased and set a new TT size if changed.
   Threads.init_hash_tables();
   TT.set_size(Options["Hash"].value<int>());
 
@@ -2142,7 +2143,7 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
 
   while (true)
   {
-      // Slave threads can exit as soon as AllThreadsShouldExit raises,
+      // Slave threads can exit as soon as allThreadsShouldExit flag raises,
       // master should exit as last one.
       if (allThreadsShouldExit)
       {
@@ -2151,7 +2152,7 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
           return;
       }
 
-      // If we are not thinking, wait for a condition to be signaled
+      // If we are not searching, wait for a condition to be signaled
       // instead of wasting CPU time polling for work.
       while (   threadID >= activeThreads
              || threads[threadID].state == Thread::INITIALIZING
@@ -2166,7 +2167,7 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
           // Grab the lock to avoid races with Thread::wake_up()
           lock_grab(&threads[threadID].sleepLock);
 
-          // If we are master and all slaves have finished do not go to sleep
+          // If we are master and all slaves have finished don't go to sleep
           for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
           allFinished = (i == activeThreads);
 
@@ -2176,7 +2177,10 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
               break;
           }
 
-          // Do sleep here after retesting sleep conditions
+          // Do sleep after retesting sleep conditions under lock protection, in
+          // particular we need to avoid a deadlock in case a master thread has,
+          // in the meanwhile, allocated us and sent the wake_up() call before we
+          // had the chance to grab the lock.
           if (threadID >= activeThreads || threads[threadID].state == Thread::AVAILABLE)
               cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock);
 
@@ -2191,7 +2195,6 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
           threads[threadID].state = Thread::SEARCHING;
 
           // Copy split point position and search stack and call search()
-          // with SplitPoint template parameter set to true.
           SearchStack ss[PLY_MAX_PLUS_2];
           SplitPoint* tsp = threads[threadID].splitPoint;
           Position pos(*tsp->pos, threadID);
@@ -2227,14 +2230,10 @@ void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
 
       if (allFinished)
       {
-          // Because sp->slaves[] is reset under lock protection,
+          // Because sp->is_slave[] is reset under lock protection,
           // be sure sp->lock has been released before to return.
           lock_grab(&(sp->lock));
           lock_release(&(sp->lock));
-
-          // In helpful master concept a master can help only a sub-tree, and
-          // because here is all finished is not possible master is booked.
-          assert(threads[threadID].state == Thread::AVAILABLE);
           return;
       }
   }