boards: qemu: leon3: fault unique to this platform

[cfriedt]

Describe the bug

I've encountered an unusual fault running the tests/posix/barriers testsuite under qemu_leon3 with the minimal C library.

For all other platforms, using the pthread_barrierattr_t attr stack variable as a stack varialbe is perfectly fine and business as usual. However, I've needed to make this variable static just on this platform to workaround the issue.

• What target platform are you using? qemu_leon3

• What have you tried to diagnose or workaround this issue?

  • I've tried all other platforms and none have this problem
  • tried stepping with CONFIG_NO_OPTIMIZATIONS=y and CONFIG_DEBUG_OPTIMIZATIONS=y
    • problem cannot be reproduced
  • tried stepping with optimizations and I've had qemu crash
  • tried increasing stack sizes, with no success
  • Workaround was to make it static just for qemu_leon3

Regression

• This is a regression.

Steps to reproduce

Check out the code in #97855 and remove the STATIC modifier of the pthread_barrierattr_t attr stack variable.

To get the fault in the log section below

twister -c -p qemu_leon3 -T tests/posix/barriers/

Relevant log output

*** Booting Zephyr OS build v4.2.0-7232-gcc8fa8e6b81d ***
Running TESTSUITE posix_barriers
===================================================================
START - test_barrier
E: 
E: tt = 0x07, mem_address_not_aligned
E: 
E:       INS        LOCALS     OUTS       GLOBALS
E:   0:  4000b4d3   40008308   00000000   00000000
E:   1:  00000000   40009d64   4000a978   40001450
E:   2:  00000001   00000000   4000a000   00000002
E:   3:  00000001   00000000   400082ec   00000007
E:   4:  4000a7f8   4000a800   00000000   00000001
E:   5:  400082ec   00000000   40008308   00001010
E:   6:  4000b470   40000060   4000b410   00000000
E:   7:  40001454   00000000   40003f60   00000000
E: 
E: psr: f30000c2   wim: 00000001   tbr: 40000070   y: 00000000
E:  pc: 40003634   npc: 40003664
E: 
E:       pc         sp
E:  #0   40003634   4000b410
E:  #1   40001454   4000b470
E:  #2   400038cc   4000b4d8
E:  #3   40001b94   4000b538
E:  #4   40002f50   4000b598
E: 
E: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
E: Current thread: 0x4000a3f0 (test_barrier)
E: Halting system

Impact

Annoyance – Minor irritation; no significant impact on usability or functionality.

Environment

• OS: Ubuntu Linux 24.04
• Toolchain: Zephyr SDK v0.17.4
• from a PR (currently) in posix: deprecate CONFIG_POSIX_API and remove zephyr/posix include prefix #97855

Additional Context

Discovered while working on #97855

[kartben]

@cfriedt

AFAIU you need to make sure that the stack variable is 4-byte aligned. The below does the trick:

diff --git a/include/zephyr/posix/sys/_pthreadtypes.h b/include/zephyr/posix/sys/_pthreadtypes.h
index dc36ea76cba..5cc263cdb92 100644
--- a/include/zephyr/posix/sys/_pthreadtypes.h
+++ b/include/zephyr/posix/sys/_pthreadtypes.h
@@ -41,7 +41,7 @@ typedef struct {
                /* avoid "empty struct has size 0 in C, size 1 in C++ [-Wextern-c-compat]" */
                uint8_t: 8;
        };
-} pthread_barrierattr_t;
+} __aligned(__alignof__(int)) pthread_barrierattr_t;
 #define _PTHREAD_BARRIERATTR_T_DECLARED
 #define __pthread_barrierattr_t_defined
 #endif

[cfriedt]

@kartben also this

diff --git a/include/zephyr/posix/sys/_pthreadtypes.h b/include/zephyr/posix/sys/_pthreadtypes.h
index dc36ea76cba..60c01ccced6 100644
--- a/include/zephyr/posix/sys/_pthreadtypes.h
+++ b/include/zephyr/posix/sys/_pthreadtypes.h
@@ -39,7 +41,7 @@ typedef struct {
                int pshared;
 #endif
                /* avoid "empty struct has size 0 in C, size 1 in C++ [-Wextern-c-compat]" */
-               uint8_t: 8;
+               int: 8;
        };
 } pthread_barrierattr_t;
 #define _PTHREAD_BARRIERATTR_T_DECLARED

[cfriedt]

Just going to close this, since it's fixed in the source PR.