@@ -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;
@@ -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;
@@ -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;
@@ -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;
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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);
@@ -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;
From: Ronan Desplanques <desplanques@adacore.com> This patch changes the task initialization subprograms on POSIX platforms so that the thread ID of an ATCB is only set once. This has the advantage of getting rid of the Atomic aspect on the corresponding record component, and silences a Helgrind warning about a data race. gcc/ada/ * libgnarl/s-taprop__linux.adb (Enter_Task): Move setting of thread ID out of Enter_Task. (Initialize): Set thread ID for the environment task. (Create_Task): Remove now unnecessary Unrestricted_Access attribute and add justification for a memory write. * libgnarl/s-taprop__posix.adb: Likewise. * libgnarl/s-taprop__qnx.adb: Likewise. * libgnarl/s-taprop__rtems.adb: Likewise. * libgnarl/s-taprop__solaris.adb: Likewise. * libgnarl/s-taspri__posix.ads: Remove pragma Atomic for Private_Data.Thread, and update documentation comment. * libgnarl/s-taspri__lynxos.ads: Likewise. * libgnarl/s-taspri__posix-noaltstack.ads: Likewise. * libgnarl/s-taspri__solaris.ads: Likewise. * libgnarl/s-tporft.adb (Register_Foreign_Thread): Adapt to Enter_Task not setting the thread ID anymore. * libgnarl/s-tassta.adb (Task_Wrapper): Update comment. Tested on x86_64-pc-linux-gnu, committed on master. --- gcc/ada/libgnarl/s-taprop__linux.adb | 14 +++++++------- gcc/ada/libgnarl/s-taprop__posix.adb | 14 +++++++------- gcc/ada/libgnarl/s-taprop__qnx.adb | 14 +++++++------- gcc/ada/libgnarl/s-taprop__rtems.adb | 14 +++++++------- gcc/ada/libgnarl/s-taprop__solaris.adb | 16 ++++++++-------- gcc/ada/libgnarl/s-taspri__lynxos.ads | 16 ++++++++++------ gcc/ada/libgnarl/s-taspri__posix-noaltstack.ads | 16 ++++++++++------ gcc/ada/libgnarl/s-taspri__posix.ads | 16 ++++++++++------ gcc/ada/libgnarl/s-taspri__solaris.ads | 16 ++++++++++------ gcc/ada/libgnarl/s-tassta.adb | 2 +- gcc/ada/libgnarl/s-tporft.adb | 1 + 11 files changed, 78 insertions(+), 61 deletions(-)