[Ada] Do not assume a priority value of zero is a valid priority
Commit Message
While a priority value of zero is typically valid on most systems, there
are some targets where zero may be reserved for OS purposes (for
example: RTEMS where zero is reserved for use by the idle thread and
should not be used by applications). This patch removes one occurrence
in GNARL where a Priority object was initialized to zero instead of
Priority'First, and adjusts the Priority type on RTEMS to prevent the
use of priority level zero. By contrast,
System.Tasking.Unspecified_Priority is hardcoded as -1 since it is used
in init.c, which does not have access to the Priority type.
Tested on x86_64-pc-linux-gnu, committed on trunk
gcc/ada/
* libgnarl/s-taskin.adb (Initialize_ATCB): Initialize
T.Common.Current_Priority to Priority'First.
* libgnarl/s-taskin.ads (Unspecified_Priority): Redefined as -1.
* libgnat/system-rtems.ads: Start priority range from 1, as 0 is
reserved by the operating system.
@@ -127,7 +127,7 @@ package body System.Tasking is
end if;
pragma Assert (T.Common.Domain /= null);
- T.Common.Current_Priority := 0;
+ T.Common.Current_Priority := Priority'First;
T.Common.Protected_Action_Nesting := 0;
T.Common.Call := null;
T.Common.Task_Arg := Task_Arg;
@@ -773,7 +773,10 @@ package System.Tasking is
-- Priority info --
-------------------
- Unspecified_Priority : constant Integer := System.Priority'First - 1;
+ Unspecified_Priority : constant Integer := -1;
+ -- Indicates that a task has an unspecified priority. This is hardcoded as
+ -- -1 rather than System.Priority'First - 1 as the value needs to be used
+ -- in init.c to specify that the main task has no specified priority.
Priority_Not_Boosted : constant Integer := System.Priority'First - 1;
-- Definition of Priority actually has to come from the RTS configuration
@@ -109,15 +109,13 @@ package System is
-- hardware priority levels. Protected Object ceilings can
-- override these values.
-- 245 is used by the Interrupt_Manager task
- -- 0 is reserved for the RTEMS IDLE task and really should not
- -- be accessible from Ada but GNAT initializes
- -- Current_Priority to 0 so it must be valid
+ -- 0 is reserved for the RTEMS IDLE task
Max_Priority : constant Positive := 244;
Max_Interrupt_Priority : constant Positive := 254;
- subtype Any_Priority is Integer range 0 .. 254;
- subtype Priority is Any_Priority range 0 .. 244;
+ subtype Any_Priority is Integer range 1 .. 254;
+ subtype Priority is Any_Priority range 1 .. 244;
subtype Interrupt_Priority is Any_Priority range 245 .. 254;
Default_Priority : constant Priority := 122;