------------------------------------------------------------------------------ -- -- -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS -- -- -- -- S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S . -- -- S I N G L E _ E N T R Y -- -- -- -- B o d y -- -- -- -- Copyright (C) 1998-2013, AdaCore -- -- -- -- GNARL is free software; you can redistribute it and/or modify it under -- -- terms of the GNU General Public License as published by the Free Soft- -- -- ware Foundation; either version 3, or (at your option) any later ver- -- -- sion. GNARL is distributed in the hope that it will be useful, but WITH- -- -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- -- or FITNESS FOR A PARTICULAR PURPOSE. -- -- -- -- -- -- -- -- -- -- -- -- You should have received a copy of the GNU General Public License and -- -- a copy of the GCC Runtime Library Exception along with this program; -- -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- -- . -- -- -- -- GNARL was developed by the GNARL team at Florida State University. -- -- Extensive contributions were provided by Ada Core Technologies, Inc. -- -- -- ------------------------------------------------------------------------------ pragma Style_Checks (All_Checks); -- Turn off subprogram ordering check, since restricted GNARLI -- subprograms are gathered together at end. -- This package provides an optimized version of Protected_Objects.Operations -- and Protected_Objects.Entries making the following assumptions: -- -- PO have only one entry -- There is only one caller at a time (No_Entry_Queue) -- There is no dynamic priority support (No_Dynamic_Priorities) -- No Abort Statements -- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0) -- PO are at library level -- No Requeue -- None of the tasks will terminate (no need for finalization) -- -- This interface is intended to be used in the ravenscar and restricted -- profiles, the compiler is responsible for ensuring that the conditions -- mentioned above are respected, except for the No_Entry_Queue restriction -- that is checked dynamically in this package, since the check cannot be -- performed at compile time (see Protected_Single_Entry_Call, Service_Entry). pragma Polling (Off); -- Turn off polling, we do not want polling to take place during tasking -- operations. It can cause infinite loops and other problems. pragma Suppress (All_Checks); with System.Multiprocessors; with System.Task_Primitives.Operations; -- used for Self -- Get_Priority -- Set_Priority with System.Tasking.Protected_Objects.Multiprocessors; package body System.Tasking.Protected_Objects.Single_Entry is use System.Multiprocessors; package STPO renames System.Task_Primitives.Operations; package STPOM renames System.Tasking.Protected_Objects.Multiprocessors; Multiprocessor : constant Boolean := CPU'Range_Length /= 1; --------------------------------- -- Initialize_Protection_Entry -- --------------------------------- procedure Initialize_Protection_Entry (Object : Protection_Entry_Access; Ceiling_Priority : Integer; Compiler_Info : System.Address; Entry_Body : Entry_Body_Access) is begin Initialize_Protection (Object.Common'Access, Ceiling_Priority); Object.Compiler_Info := Compiler_Info; Object.Call_In_Progress := null; Object.Entry_Body := Entry_Body; Object.Entry_Queue := null; end Initialize_Protection_Entry; ---------------- -- Lock_Entry -- ---------------- procedure Lock_Entry (Object : Protection_Entry_Access) is begin Lock (Object.Common'Access); end Lock_Entry; ---------------------------- -- Protected_Single_Count -- ---------------------------- function Protected_Count_Entry (Object : Protection_Entry) return Natural is begin return Boolean'Pos (Object.Entry_Queue /= null); end Protected_Count_Entry; --------------------------------- -- Protected_Single_Entry_Call -- --------------------------------- procedure Protected_Single_Entry_Call (Object : Protection_Entry_Access; Uninterpreted_Data : System.Address) is Self_Id : constant Task_Id := STPO.Self; begin -- For this run time, pragma Detect_Blocking is always active, so we -- must raise Program_Error if this potentially blocking operation is -- called from a protected action. if Self_Id.Common.Protected_Action_Nesting > 0 then raise Program_Error; end if; Lock_Entry (Object); Self_Id.Entry_Call.Uninterpreted_Data := Uninterpreted_Data; if Object.Entry_Body.Barrier (Object.Compiler_Info, 1) then -- No other task can be executing an entry within this protected -- object. On a single processor implementation (such as this one), -- the ceiling priority protocol and the strictly preemptive priority -- scheduling policy guarantee that protected objects are always -- available when any task tries to use them (otherwise, either the -- currently executing task would not have had a high enough priority -- to be executing, or a blocking operation would have been called -- from within the entry body). pragma Assert (Object.Call_In_Progress = null); Object.Call_In_Progress := Self_Id.Entry_Call'Access; Object.Entry_Body.Action (Object.Compiler_Info, Self_Id.Entry_Call.Uninterpreted_Data, 1); Object.Call_In_Progress := null; -- Entry call is over Unlock_Entry (Object); else if Object.Entry_Queue /= null then -- This violates the No_Entry_Queue restriction, raise -- Program_Error. Unlock_Entry (Object); raise Program_Error; end if; -- There is a potential race condition between the Unlock_Entry and -- the Sleep below (the Wakeup may be called before the Sleep). This -- case is explicitly handled in the Sleep and Wakeup procedures: -- Sleep won't block if Wakeup has been called before. Object.Entry_Queue := Self_Id.Entry_Call'Access; Unlock_Entry (Object); -- Suspend until entry call has been completed. -- On exit, the call will not be queued. Self_Id.Common.State := Entry_Caller_Sleep; STPO.Sleep (Self_Id, Entry_Caller_Sleep); Self_Id.Common.State := Runnable; end if; end Protected_Single_Entry_Call; ----------------------------------- -- Protected_Single_Entry_Caller -- ----------------------------------- function Protected_Single_Entry_Caller (Object : Protection_Entry) return Task_Id is begin return Object.Call_In_Progress.Self; end Protected_Single_Entry_Caller; ------------------- -- Service_Entry -- ------------------- procedure Service_Entry (Object : Protection_Entry_Access) is Entry_Call : constant Entry_Call_Link := Object.Entry_Queue; Caller : Task_Id; begin if Entry_Call /= null and then Object.Entry_Body.Barrier (Object.Compiler_Info, 1) then Object.Entry_Queue := null; -- No other task can be executing an entry within this protected -- object. On a single processor implementation (such as this one), -- the ceiling priority protocol and the strictly preemptive -- priority scheduling policy guarantee that protected objects are -- always available when any task tries to use them (otherwise, -- either the currently executing task would not have had a high -- enough priority to be executing, or a blocking operation would -- have been called from within the entry body). pragma Assert (Object.Call_In_Progress = null); Object.Call_In_Progress := Entry_Call; Object.Entry_Body.Action (Object.Compiler_Info, Entry_Call.Uninterpreted_Data, 1); Object.Call_In_Progress := null; Caller := Entry_Call.Self; Unlock_Entry (Object); -- Signal the entry caller that the entry is completed if not Multiprocessor or else Caller.Common.Base_CPU = STPO.Self.Common.Base_CPU then -- Entry caller and servicing tasks are on the same CPU. -- We are allowed to directly wake up the task. STPO.Wakeup (Caller, Entry_Caller_Sleep); else -- The entry caller is on a different CPU. STPOM.Served (Entry_Call); end if; else -- Just unlock the entry Unlock_Entry (Object); end if; end Service_Entry; ------------------ -- Unlock_Entry -- ------------------ procedure Unlock_Entry (Object : Protection_Entry_Access) is begin Unlock (Object.Common'Access); end Unlock_Entry; end System.Tasking.Protected_Objects.Single_Entry;