* [Ada] Ensure System.Tasking.Debug.Known_Tasks component access is atomic
@ 2021-06-30 9:30 Pierre-Marie de Rodat
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From: Pierre-Marie de Rodat @ 2021-06-30 9:30 UTC (permalink / raw)
To: gcc-patches
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Multiple threads can access the elements of
System.Tasking.Debug.Known_Tasks concurrently. While the compiler will
generally produce code that reads and writes Task_Ids atomically since
Task_Id is word size, it is best to be explicit to prevent data race
issues that may arise from non-atomic component accesses.
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* libgnarl/s-tasdeb.ads (Known_Tasks): Add Atomic_Components
aspect.
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diff --git a/gcc/ada/libgnarl/s-tasdeb.ads b/gcc/ada/libgnarl/s-tasdeb.ads
--- a/gcc/ada/libgnarl/s-tasdeb.ads
+++ b/gcc/ada/libgnarl/s-tasdeb.ads
@@ -65,9 +65,11 @@ package System.Tasking.Debug is
-- General GDB support --
-------------------------
- Known_Tasks : array (0 .. 999) of Task_Id := (others => null);
+ Known_Tasks : array (0 .. 999) of Task_Id := (others => null)
+ with Atomic_Components;
-- Global array of tasks read by gdb, and updated by Create_Task and
- -- Finalize_TCB
+ -- Finalize_TCB. Ensure access to its components is atomic to allow
+ -- lock-free concurrent access.
Debug_Event_Activating : constant := 1;
Debug_Event_Run : constant := 2;
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