newlib threadsafe: Control allocation through thread flag

[jnohlgard]

Example proof of concept for introducing a thread flag for allocating a thread local reentrancy struct.

See tests/thread_msg for an example printout of thread local vs. global reent pointers.
Threads main and nr3 have thread local reents, threads nr1, nr2 use the global reent struct.

[jnohlgard]

Example output, note that the stack usage on the idle thread has not increased because it uses the global reent struct (__global_impure_ptr). However, all threads which have per thread allocated reentrancy has increased their stack usage by 116 bytes.

2018-02-27 15:31:02,925 - INFO # main(): This is RIOT! (Version: 2018.04-devel-395-gd87ed7-cheesecake-spr/newlib-threadsafe)
2018-02-27 15:31:02,926 - INFO # PID    2 reent: 0x1fff0d40
2018-02-27 15:31:02,928 - INFO # 	pid | name                 | state    Q | pri | stack  ( used) | base addr  | current     
2018-02-27 15:31:02,941 - INFO # 	  - | isr_stack            | -        - |   - |    512 (  184) | 0x1fff0000 | 0x1fff01c8
2018-02-27 15:31:02,942 - INFO # 	  1 | idle                 | pending  Q |  15 |    384 (  124) | 0x1fff05d8 | 0x1fff06dc 
2018-02-27 15:31:02,957 - INFO # 	  2 | main                 | running  Q |   7 |   1664 (  572) | 0x1fff0758 | 0x1fff0cf4 
2018-02-27 15:31:02,958 - INFO # 	    | SUM                  |            |     |   2560 (  880)
2018-02-27 15:31:02,958 - INFO # THREADS CREATED
2018-02-27 15:31:02,958 - INFO # 
2018-02-27 15:31:02,973 - INFO # 	pid | name                 | state    Q | pri | stack  ( used) | base addr  | current     
2018-02-27 15:31:02,975 - INFO # 	  - | isr_stack            | -        - |   - |    512 (  184) | 0x1fff0000 | 0x1fff01c8
2018-02-27 15:31:02,989 - INFO # 	  1 | idle                 | pending  Q |  15 |    384 (  124) | 0x1fff05d8 | 0x1fff06dc 
2018-02-27 15:31:02,990 - INFO # 	  2 | main                 | running  Q |   7 |   1664 (  572) | 0x1fff0758 | 0x1fff0cf4 
2018-02-27 15:31:03,005 - INFO # 	  3 | nr1                  | pending  Q |   6 |   1664 (  128) | 0x1fff1074 | 0x1fff1674 
2018-02-27 15:31:03,007 - INFO # 	  4 | nr2                  | pending  Q |   6 |   1664 (  128) | 0x1fff16f4 | 0x1fff1cf4 
2018-02-27 15:31:03,021 - INFO # 	  5 | nr3                  | pending  Q |   6 |   1664 (  224) | 0x1fff1d74 | 0x1fff2314 
2018-02-27 15:31:03,021 - INFO # 	    | SUM                  |            |     |   7552 ( 1360)
2018-02-27 15:31:03,022 - INFO # THREAD 1 start
2018-02-27 15:31:03,022 - INFO # 
2018-02-27 15:31:03,022 - INFO # PID    3 reent: 0x1fff02a8
2018-02-27 15:31:03,023 - INFO # THREAD 2 start
2018-02-27 15:31:03,023 - INFO # 
2018-02-27 15:31:03,036 - INFO # PID    4 reent: 0x1fff02a8
2018-02-27 15:31:03,037 - INFO # THREAD 3 start
2018-02-27 15:31:03,037 - INFO # 
2018-02-27 15:31:03,037 - INFO # PID    5 reent: 0x1fff235c
2018-02-27 15:31:03,037 - INFO # T3 i=0
2018-02-27 15:31:03,037 - INFO # T3 i=1
2018-02-27 15:31:03,037 - INFO # T1 recv: 0(i=0)
2018-02-27 15:31:03,038 - INFO # T2 got 0 (i=0)
2018-02-27 15:31:03,038 - INFO # T1 got reply: 0 (i=0)
2018-02-27 15:31:03,038 - INFO # T1 recv: 1(i=1)
2018-02-27 15:31:03,038 - INFO # T3 i=2
2018-02-27 15:31:03,039 - INFO # T2 got 1 (i=1)
2018-02-27 15:31:03,039 - INFO # T1 got reply: 1 (i=1)
2018-02-27 15:31:03,052 - INFO # T1 recv: 2(i=2)
2018-02-27 15:31:03,053 - INFO # T3 i=3
2018-02-27 15:31:03,053 - INFO # T2 got 2 (i=2)
2018-02-27 15:31:03,053 - INFO # T1 got reply: 2 (i=2)
2018-02-27 15:31:03,053 - INFO # THREAD 1 end
2018-02-27 15:31:03,053 - INFO # 
2018-02-27 15:31:03,054 - INFO # SUCCESS

[vincent-d]

Looks good.

I'm just wondering if __global_impure_ptr is meant to be used like this. But I can't find any useful documentation on this...

[jnohlgard]

I'm not sure either. I am also not sure which reent will be used from interrupt context, I assume it will be whatever thread was active when the interrupt happened.

[jnohlgard]

I have tested this very little, just wrote it to prove to myself that it would work like this. The documentation on the internals of newlib are pretty scarce.