diff mbox series

[COMMITTED,10/31] ada: Remove some explicit yields in tasking run-time

Message ID 20240521073035.314024-10-poulhies@adacore.com
State New
Headers show
Series [COMMITTED,01/31] ada: Add new Mingw task priority mapping | expand

Commit Message

Marc Poulhiès May 21, 2024, 7:30 a.m. UTC 
From: Ronan Desplanques <desplanques@adacore.com>

This patch removes three occurrences where tasking run-time
subprograms yielded control shortly before conditional calls to Sleep,
in order to avoid these calls more often. It was intended as an
optimization on systems where calls to Sleep are costly and in
particular VMS.

A problem was that two of the yields contained data races that were
reported by thread sanitizing tools on some platforms, and that's the
motivation for removing them.

gcc/ada/

	* libgnarl/s-taenca.adb (Wait_For_Completion): Remove call to
	Yield.
	* libgnarl/s-tasren.adb (Timed_Selective_Wait, Wait_For_Call):
	Remove calls to Yield.

Tested on x86_64-pc-linux-gnu, committed on master.

---
 gcc/ada/libgnarl/s-taenca.adb | 12 ------------
 gcc/ada/libgnarl/s-tasren.adb | 24 ------------------------
 2 files changed, 36 deletions(-)
diff mbox series

Patch

diff --git a/gcc/ada/libgnarl/s-taenca.adb b/gcc/ada/libgnarl/s-taenca.adb
index cd9c53b19fe..1dc8ec518bd 100644
--- a/gcc/ada/libgnarl/s-taenca.adb
+++ b/gcc/ada/libgnarl/s-taenca.adb
@@ -410,18 +410,6 @@  package body System.Tasking.Entry_Calls is
 
       Self_Id.Common.State := Entry_Caller_Sleep;
 
-      --  Try to remove calls to Sleep in the loop below by letting the caller
-      --  a chance of getting ready immediately, using Unlock & Yield.
-      --  See similar action in Wait_For_Call & Timed_Selective_Wait.
-
-      STPO.Unlock (Self_Id);
-
-      if Entry_Call.State < Done then
-         STPO.Yield;
-      end if;
-
-      STPO.Write_Lock (Self_Id);
-
       loop
          Check_Pending_Actions_For_Entry_Call (Self_Id, Entry_Call);
 
diff --git a/gcc/ada/libgnarl/s-tasren.adb b/gcc/ada/libgnarl/s-tasren.adb
index d65b9f011b0..6face7ef8d4 100644
--- a/gcc/ada/libgnarl/s-tasren.adb
+++ b/gcc/ada/libgnarl/s-tasren.adb
@@ -1317,18 +1317,6 @@  package body System.Tasking.Rendezvous is
 
             Self_Id.Common.State := Acceptor_Delay_Sleep;
 
-            --  Try to remove calls to Sleep in the loop below by letting the
-            --  caller a chance of getting ready immediately, using Unlock
-            --  Yield. See similar action in Wait_For_Completion/Wait_For_Call.
-
-            Unlock (Self_Id);
-
-            if Self_Id.Open_Accepts /= null then
-               Yield;
-            end if;
-
-            Write_Lock (Self_Id);
-
             --  Check if this task has been aborted while the lock was released
 
             if Self_Id.Pending_ATC_Level < Self_Id.ATC_Nesting_Level then
@@ -1510,18 +1498,6 @@  package body System.Tasking.Rendezvous is
    begin
       Self_Id.Common.State := Acceptor_Sleep;
 
-      --  Try to remove calls to Sleep in the loop below by letting the caller
-      --  a chance of getting ready immediately, using Unlock & Yield.
-      --  See similar action in Wait_For_Completion & Timed_Selective_Wait.
-
-      Unlock (Self_Id);
-
-      if Self_Id.Open_Accepts /= null then
-         Yield;
-      end if;
-
-      Write_Lock (Self_Id);
-
       --  Check if this task has been aborted while the lock was released
 
       if Self_Id.Pending_ATC_Level < Self_Id.ATC_Nesting_Level then