[COMMITTED,14/30] ada: Tweak handling of thread ID on POSIX

diff --git a/gcc/ada/libgnarl/s-taprop__linux.adb b/gcc/ada/libgnarl/s-taprop__linux.adb
index 0c09817739c..0a51b3601c0 100644
--- a/gcc/ada/libgnarl/s-taprop__linux.adb
+++ b/gcc/ada/libgnarl/s-taprop__linux.adb
@@ -730,7 +730,6 @@  package body System.Task_Primitives.Operations is
          raise Invalid_CPU_Number;
       end if;
 
-      Self_ID.Common.LL.Thread := pthread_self;
       Self_ID.Common.LL.LWP := lwp_self;
 
       --  Set thread name to ease debugging. If the name of the task is
@@ -1004,14 +1003,14 @@  package body System.Task_Primitives.Operations is
       --  do not need to manipulate caller's signal mask at this point.
       --  All tasks in RTS will have All_Tasks_Mask initially.
 
-      --  Note: the use of Unrestricted_Access in the following call is needed
-      --  because otherwise we have an error of getting a access-to-volatile
-      --  value which points to a non-volatile object. But in this case it is
-      --  safe to do this, since we know we have no problems with aliasing and
-      --  Unrestricted_Access bypasses this check.
+      --  The write to T.Common.LL.Thread is not racy with regard to the
+      --  created thread because the created thread will not access it until
+      --  we release the RTS lock (or the current task's lock when
+      --  Restricted.Stages is used). One can verify that by inspecting the
+      --  Task_Wrapper procedures.
 
       Result := pthread_create
-        (T.Common.LL.Thread'Unrestricted_Access,
+        (T.Common.LL.Thread'Access,
          Thread_Attr'Access,
          Thread_Body_Access (Wrapper),
          To_Address (T));
@@ -1385,6 +1384,7 @@  package body System.Task_Primitives.Operations is
 
    begin
       Environment_Task_Id := Environment_Task;
+      Environment_Task.Common.LL.Thread := pthread_self;
 
       Interrupt_Management.Initialize;
 
diff --git a/gcc/ada/libgnarl/s-taprop__posix.adb b/gcc/ada/libgnarl/s-taprop__posix.adb
index 7ed52ea2d82..fb70aaf4976 100644
--- a/gcc/ada/libgnarl/s-taprop__posix.adb
+++ b/gcc/ada/libgnarl/s-taprop__posix.adb
@@ -636,7 +636,6 @@  package body System.Task_Primitives.Operations is
 
    procedure Enter_Task (Self_ID : Task_Id) is
    begin
-      Self_ID.Common.LL.Thread := pthread_self;
       Self_ID.Common.LL.LWP := lwp_self;
 
       Specific.Set (Self_ID);
@@ -841,14 +840,14 @@  package body System.Task_Primitives.Operations is
       --  do not need to manipulate caller's signal mask at this point.
       --  All tasks in RTS will have All_Tasks_Mask initially.
 
-      --  Note: the use of Unrestricted_Access in the following call is needed
-      --  because otherwise we have an error of getting a access-to-volatile
-      --  value which points to a non-volatile object. But in this case it is
-      --  safe to do this, since we know we have no problems with aliasing and
-      --  Unrestricted_Access bypasses this check.
+      --  The write to T.Common.LL.Thread is not racy with regard to the
+      --  created thread because the created thread will not access it until
+      --  we release the RTS lock (or the current task's lock when
+      --  Restricted.Stages is used). One can verify that by inspecting the
+      --  Task_Wrapper procedures.
 
       Result := pthread_create
-        (T.Common.LL.Thread'Unrestricted_Access,
+        (T.Common.LL.Thread'Access,
          Attributes'Access,
          Thread_Body_Access (Wrapper),
          To_Address (T));
@@ -1260,6 +1259,7 @@  package body System.Task_Primitives.Operations is
 
    begin
       Environment_Task_Id := Environment_Task;
+      Environment_Task.Common.LL.Thread := pthread_self;
 
       Interrupt_Management.Initialize;
 
diff --git a/gcc/ada/libgnarl/s-taprop__qnx.adb b/gcc/ada/libgnarl/s-taprop__qnx.adb
index 108180d0617..f475c05c562 100644
--- a/gcc/ada/libgnarl/s-taprop__qnx.adb
+++ b/gcc/ada/libgnarl/s-taprop__qnx.adb
@@ -654,7 +654,6 @@  package body System.Task_Primitives.Operations is
 
    procedure Enter_Task (Self_ID : Task_Id) is
    begin
-      Self_ID.Common.LL.Thread := pthread_self;
       Self_ID.Common.LL.LWP := lwp_self;
 
       Specific.Set (Self_ID);
@@ -846,14 +845,14 @@  package body System.Task_Primitives.Operations is
       --  do not need to manipulate caller's signal mask at this point.
       --  All tasks in RTS will have All_Tasks_Mask initially.
 
-      --  Note: the use of Unrestricted_Access in the following call is needed
-      --  because otherwise we have an error of getting a access-to-volatile
-      --  value which points to a non-volatile object. But in this case it is
-      --  safe to do this, since we know we have no problems with aliasing and
-      --  Unrestricted_Access bypasses this check.
+      --  The write to T.Common.LL.Thread is not racy with regard to the
+      --  created thread because the created thread will not access it until
+      --  we release the RTS lock (or the current task's lock when
+      --  Restricted.Stages is used). One can verify that by inspecting the
+      --  Task_Wrapper procedures.
 
       Result := pthread_create
-        (T.Common.LL.Thread'Unrestricted_Access,
+        (T.Common.LL.Thread'Access,
          Attributes'Access,
          Thread_Body_Access (Wrapper),
          To_Address (T));
@@ -1261,6 +1260,7 @@  package body System.Task_Primitives.Operations is
 
    begin
       Environment_Task_Id := Environment_Task;
+      Environment_Task.Common.LL.Thread := pthread_self;
 
       Interrupt_Management.Initialize;
 
diff --git a/gcc/ada/libgnarl/s-taprop__rtems.adb b/gcc/ada/libgnarl/s-taprop__rtems.adb
index 3feafd8bc3a..ea8422cb454 100644
--- a/gcc/ada/libgnarl/s-taprop__rtems.adb
+++ b/gcc/ada/libgnarl/s-taprop__rtems.adb
@@ -646,7 +646,6 @@  package body System.Task_Primitives.Operations is
 
    procedure Enter_Task (Self_ID : Task_Id) is
    begin
-      Self_ID.Common.LL.Thread := pthread_self;
       Self_ID.Common.LL.LWP := lwp_self;
 
       Specific.Set (Self_ID);
@@ -851,14 +850,14 @@  package body System.Task_Primitives.Operations is
       --  do not need to manipulate caller's signal mask at this point.
       --  All tasks in RTS will have All_Tasks_Mask initially.
 
-      --  Note: the use of Unrestricted_Access in the following call is needed
-      --  because otherwise we have an error of getting a access-to-volatile
-      --  value which points to a non-volatile object. But in this case it is
-      --  safe to do this, since we know we have no problems with aliasing and
-      --  Unrestricted_Access bypasses this check.
+      --  The write to T.Common.LL.Thread is not racy with regard to the
+      --  created thread because the created thread will not access it until
+      --  we release the RTS lock (or the current task's lock when
+      --  Restricted.Stages is used). One can verify that by inspecting the
+      --  Task_Wrapper procedures.
 
       Result := pthread_create
-        (T.Common.LL.Thread'Unrestricted_Access,
+        (T.Common.LL.Thread'Access,
          Attributes'Access,
          Thread_Body_Access (Wrapper),
          To_Address (T));
@@ -1270,6 +1269,7 @@  package body System.Task_Primitives.Operations is
 
    begin
       Environment_Task_Id := Environment_Task;
+      Environment_Task.Common.LL.Thread := pthread_self;
 
       Interrupt_Management.Initialize;
 
diff --git a/gcc/ada/libgnarl/s-taprop__solaris.adb b/gcc/ada/libgnarl/s-taprop__solaris.adb
index 82e51b8d25c..09f90e6e204 100644
--- a/gcc/ada/libgnarl/s-taprop__solaris.adb
+++ b/gcc/ada/libgnarl/s-taprop__solaris.adb
@@ -424,6 +424,7 @@  package body System.Task_Primitives.Operations is
 
    begin
       Environment_Task_Id := Environment_Task;
+      Self_ID.Common.LL.Thread := thr_self;
 
       Interrupt_Management.Initialize;
 
@@ -868,8 +869,7 @@  package body System.Task_Primitives.Operations is
 
    procedure Enter_Task (Self_ID : Task_Id) is
    begin
-      Self_ID.Common.LL.Thread := thr_self;
-      Self_ID.Common.LL.LWP    := lwp_self;
+      Self_ID.Common.LL.LWP := lwp_self;
 
       Set_Task_Affinity (Self_ID);
       Specific.Set (Self_ID);
@@ -997,11 +997,11 @@  package body System.Task_Primitives.Operations is
          Opts := THR_DETACHED + THR_BOUND;
       end if;
 
-      --  Note: the use of Unrestricted_Access in the following call is needed
-      --  because otherwise we have an error of getting a access-to-volatile
-      --  value which points to a non-volatile object. But in this case it is
-      --  safe to do this, since we know we have no problems with aliasing and
-      --  Unrestricted_Access bypasses this check.
+      --  The write to T.Common.LL.Thread is not racy with regard to the
+      --  created thread because the created thread will not access it until
+      --  we release the RTS lock (or the current task's lock when
+      --  Restricted.Stages is used). One can verify that by inspecting the
+      --  Task_Wrapper procedures.
 
       Result :=
         thr_create
@@ -1010,7 +1010,7 @@  package body System.Task_Primitives.Operations is
            Thread_Body_Access (Wrapper),
            To_Address (T),
            Opts,
-           T.Common.LL.Thread'Unrestricted_Access);
+           T.Common.LL.Thread'Access);
 
       Succeeded := Result = 0;
       pragma Assert
diff --git a/gcc/ada/libgnarl/s-taspri__lynxos.ads b/gcc/ada/libgnarl/s-taspri__lynxos.ads
index a3307000c80..f5e434eada6 100644
--- a/gcc/ada/libgnarl/s-taspri__lynxos.ads
+++ b/gcc/ada/libgnarl/s-taspri__lynxos.ads
@@ -86,12 +86,16 @@  private
 
    type Private_Data is limited record
       Thread : aliased System.OS_Interface.pthread_t;
-      pragma Atomic (Thread);
-      --  Thread field may be updated by two different threads of control.
-      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
-      --  value (thr_self value). We do not want to use lock on those
-      --  operations and the only thing we have to make sure is that they are
-      --  updated in atomic fashion.
+      --  This component is written to once before concurrent access to it is
+      --  possible, and then remains constant. The place where it is written to
+      --  depends on how the enclosing ATCB comes into existence:
+      --
+      --  1. For the environment task, the component is set in
+      --     System.Task_Primitive.Operations.Initialize.
+      --  2. For foreign threads, it happens in
+      --     System.Task_Primitives.Operations.Register_Foreign_Thread.
+      --  3. For others tasks, it's in
+      --     System.Task_Primitives.Operations.Create_Task.
 
       LWP : aliased System.OS_Interface.pthread_t;
       --  The purpose of this field is to provide a better tasking support on
diff --git a/gcc/ada/libgnarl/s-taspri__posix-noaltstack.ads b/gcc/ada/libgnarl/s-taspri__posix-noaltstack.ads
index b92f1dd4ab2..fb7e07d10cd 100644
--- a/gcc/ada/libgnarl/s-taspri__posix-noaltstack.ads
+++ b/gcc/ada/libgnarl/s-taspri__posix-noaltstack.ads
@@ -89,12 +89,16 @@  private
 
    type Private_Data is limited record
       Thread : aliased System.OS_Interface.pthread_t;
-      pragma Atomic (Thread);
-      --  Thread field may be updated by two different threads of control.
-      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
-      --  value (thr_self value). We do not want to use lock on those
-      --  operations and the only thing we have to make sure is that they are
-      --  updated in atomic fashion.
+      --  This component is written to once before concurrent access to it is
+      --  possible, and then remains constant. The place where it is written to
+      --  depends on how the enclosing ATCB comes into existence:
+      --
+      --  1. For the environment task, the component is set in
+      --     System.Task_Primitive.Operations.Initialize.
+      --  2. For foreign threads, it happens in
+      --     System.Task_Primitives.Operations.Register_Foreign_Thread.
+      --  3. For others tasks, it's in
+      --     System.Task_Primitives.Operations.Create_Task.
 
       LWP : aliased System.Address;
       --  The purpose of this field is to provide a better tasking support on
diff --git a/gcc/ada/libgnarl/s-taspri__posix.ads b/gcc/ada/libgnarl/s-taspri__posix.ads
index 4d0b379556d..3453f4fea4c 100644
--- a/gcc/ada/libgnarl/s-taspri__posix.ads
+++ b/gcc/ada/libgnarl/s-taspri__posix.ads
@@ -88,12 +88,16 @@  private
 
    type Private_Data is limited record
       Thread : aliased System.OS_Interface.pthread_t;
-      pragma Atomic (Thread);
-      --  Thread field may be updated by two different threads of control.
-      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
-      --  value (thr_self value). We do not want to use lock on those
-      --  operations and the only thing we have to make sure is that they are
-      --  updated in atomic fashion.
+      --  This component is written to once before concurrent access to it is
+      --  possible, and then remains constant. The place where it is written to
+      --  depends on how the enclosing ATCB comes into existence:
+      --
+      --  1. For the environment task, the component is set in
+      --     System.Task_Primitive.Operations.Initialize.
+      --  2. For foreign threads, it happens in
+      --     System.Task_Primitives.Operations.Register_Foreign_Thread.
+      --  3. For others tasks, it's in
+      --     System.Task_Primitives.Operations.Create_Task.
 
       LWP : aliased System.Address;
       --  The purpose of this field is to provide a better tasking support on
diff --git a/gcc/ada/libgnarl/s-taspri__solaris.ads b/gcc/ada/libgnarl/s-taspri__solaris.ads
index 16fc4196b00..586c971dce6 100644
--- a/gcc/ada/libgnarl/s-taspri__solaris.ads
+++ b/gcc/ada/libgnarl/s-taspri__solaris.ads
@@ -95,12 +95,16 @@  private
 
    type Private_Data is limited record
       Thread : aliased System.OS_Interface.thread_t;
-      pragma Atomic (Thread);
-      --  Thread field may be updated by two different threads of control.
-      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
-      --  value (thr_self value). We do not want to use lock on those
-      --  operations and the only thing we have to make sure is that they are
-      --  updated in atomic fashion.
+      --  This component is written to once before concurrent access to it is
+      --  possible, and then remains constant. The place where it is written to
+      --  depends on how the enclosing ATCB comes into existence:
+      --
+      --  1. For the environment task, the component is set in
+      --     System.Task_Primitive.Operations.Initialize.
+      --  2. For foreign threads, it happens in
+      --     System.Task_Primitives.Operations.Register_Foreign_Thread.
+      --  3. For others tasks, it's in
+      --     System.Task_Primitives.Operations.Create_Task.
 
       LWP : System.OS_Interface.lwpid_t;
       --  The LWP id of the thread. Set by self in Enter_Task
diff --git a/gcc/ada/libgnarl/s-tassta.adb b/gcc/ada/libgnarl/s-tassta.adb
index 01c94b950ba..594a1672866 100644
--- a/gcc/ada/libgnarl/s-tassta.adb
+++ b/gcc/ada/libgnarl/s-tassta.adb
@@ -1079,7 +1079,7 @@  package body System.Tasking.Stages is
       Stack_Guard (Self_ID, True);
 
       --  Initialize low-level TCB components, that cannot be initialized by
-      --  the creator. Enter_Task sets Self_ID.LL.Thread.
+      --  the creator.
 
       Enter_Task (Self_ID);
 
diff --git a/gcc/ada/libgnarl/s-tporft.adb b/gcc/ada/libgnarl/s-tporft.adb
index a7b4ce5e29a..66a9f02656e 100644
--- a/gcc/ada/libgnarl/s-tporft.adb
+++ b/gcc/ada/libgnarl/s-tporft.adb
@@ -98,6 +98,7 @@  begin
    System.Soft_Links.Create_TSD
      (Self_Id.Common.Compiler_Data, null, Sec_Stack_Size);
 
+   Self_Id.Common.LL.Thread := Thread;
    Enter_Task (Self_Id);
 
    return Self_Id;