testatomic sometime segfaults on Ubuntu arm64 builders

[seb128]

On the current Ubuntu Kinetic serie, the 2.0.22 build fails on our arm64 builders due a segfault in testatomic. The error is not consistent, tweaking the build to call it under gdb it sometime work and next try success on the same machine

Build log https://launchpadlibrarian.net/605075249/buildlog_ubuntu-kinetic-arm64.libsdl2_2.0.22+dfsg-4ubuntu3.6_BUILDING.txt.gz

INFO: 
spin lock---------------------------------------

INFO: AtomicLock                   lock=1
INFO: AtomicUnlock                 lock=0
INFO: 
atomic -----------------------------------------

INFO: AtomicSet(10)        tfret=TRUE val=10
INFO: AtomicAdd(10)        tfret=TRUE val=20
INFO: AtomicIncRef()       tfret=TRUE val=1
INFO: AtomicIncRef()       tfret=TRUE val=2
INFO: AtomicDecRef()       tfret=TRUE val=1
INFO: AtomicDecRef()       tfret=TRUE val=0
INFO: AtomicCAS()          tfret=TRUE val=10
INFO: AtomicCAS()          tfret=TRUE val=20
INFO: 
epic test---------------------------------------

INFO: Size asserted to be >= 32-bit
INFO: Check static initializer
INFO: Test negative values
INFO: Verify maximum value
INFO: Test compare and exchange
INFO: Test Add
INFO: Test Add (Negative values)
INFO: Reset before count down test
INFO: Counting down from 2147483647, Expect 47 remaining
INFO: Thread subtracting 100 10737418 times
[New Thread 0xfffff6b8f060 (LWP 28956)]
INFO: Thread subtracting 100 10737418 times
[New Thread 0xfffff637f060 (LWP 28957)]
[Thread 0xfffff6b8f060 (LWP 28956) exited]
INFO: Finished in 0.938000 sec
INFO: Atomic 47 Non-Atomic 105733847
INFO: 
FIFO test---------------------------------------

INFO: Mode: LockFree
INFO: Starting 4 readers
[Thread 0xfffff637f060 (LWP 28957) exited]
[New Thread 0xfffff5b6f060 (LWP 28958)]
[New Thread 0xfffff535f060 (LWP 28959)]
[New Thread 0xfffff4b4f060 (LWP 28960)]
[New Thread 0xfffff433f060 (LWP 28961)]
INFO: Starting 4 writers
[New Thread 0xfffff3b2f060 (LWP 28962)]
[New Thread 0xfffff331f060 (LWP 28963)]
[New Thread 0xfffff2b0f060 (LWP 28964)]
[New Thread 0xfffff22ff060 (LWP 28965)]
[New Thread 0xfffff1aef060 (LWP 28966)]
[Thread 0xfffff331f060 (LWP 28963) exited]
[Thread 0xfffff22ff060 (LWP 28965) exited]
[Thread 0xfffff2b0f060 (LWP 28964) exited]
INFO: Finished in 2.452000 sec
INFO: 
INFO: Writer 0 wrote 1000000 events, had 2124 waits
INFO: Writer 1 wrote 1000000 events, had 2172 waits
INFO: Writer 2 wrote 1000000 events, had 2179 waits
INFO: Writer 3 wrote 1000000 events, had 2151 waits
INFO: Writers wrote 4000000 total events
INFO: 
INFO: Reader 0 read 1000625 events, had 2276 waits
INFO:   { 251107, 247128, 247428, 254962 }
INFO: Reader 1 read 1003625 events, had 2273 waits
INFO:   { 255642, 247382, 250705, 249896 }
INFO: Reader 2 read 1020974 events, had 2351 waits
INFO:   { 254639, 256773, 252382, 257180 }
INFO: Reader 3 read 974776 events, had 2228 waits
INFO:   { 238612, 248717, 249485, 237962 }
INFO: Readers read 4000000 total events
[Thread 0xfffff1aef060 (LWP 28966) exited]
[Thread 0xfffff3b2f060 (LWP 28962) exited]
[Thread 0xfffff433f060 (LWP 28961) exited]
[Thread 0xfffff4b4f060 (LWP 28960) exited]
[Thread 0xfffff535f060 (LWP 28959) exited]

Thread 1 "testatomic" received signal SIGSEGV, Segmentation fault.
__run_exit_handlers (status=0, listp=0xfffff7e0c730 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at ./stdlib/exit.c:90
90	./stdlib/exit.c: No such file or directory.

Thread 4 (Thread 0xfffff5b6f060 (LWP 28958) "FIFOWatcher"):
#0  0x0000fffff7d21928 in __GI___clock_nanosleep (clock_id=<optimized out>, clock_id@entry=0, flags=flags@entry=0, req=req@entry=0xfffff5b6e618, rem=rem@entry=0xfffff5b6e628) at ../sysdeps/unix/sysv/linux/clock_nanosleep.c:78
#1  0x0000fffff7d26aec in __GI___nanosleep (req=req@entry=0xfffff5b6e618, rem=rem@entry=0xfffff5b6e628) at ../sysdeps/unix/sysv/linux/nanosleep.c:25
#2  0x0000fffff7f2eb0c in SDL_Delay_REAL (ms=<optimized out>) at ./src/timer/unix/SDL_systimer.c:220
#3  0x0000fffff7e49fac in SDL_AtomicLock_REAL (lock=0xffffffffec28) at ./src/atomic/SDL_spinlock.c:171
#4  0x0000aaaaaaaab818 in FIFO_Watcher (_data=0xffffffffaaa8) at ../../test/testatomic.c:574
#5  0x0000fffff7f23254 in SDL_RunThread (thread=0xaaaaaaad0400) at ./src/thread/SDL_thread.c:275
#6  RunThread (data=0xaaaaaaad0400) at ./src/thread/pthread/SDL_systhread.c:77
#7  0x0000fffff7ced5c8 in start_thread (arg=0x0) at ./nptl/pthread_create.c:442
#8  0x0000fffff7d55d1c in thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:79

Thread 1 (Thread 0xfffff7c64460 (LWP 28954) "testatomic"):
#0  __run_exit_handlers (status=0, listp=0xfffff7e0c730 <__exit_funcs>, run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true) at ./stdlib/exit.c:90
#1  0x0000fffff7cacf0c in __GI_exit (status=<optimized out>) at ./stdlib/exit.c:143
#2  0x0000fffff7c97400 in __libc_start_call_main (main=main@entry=0xaaaaaaaaad40 <main>, argc=argc@entry=1, argv=argv@entry=0xffffffffee98) at ../sysdeps/nptl/libc_start_call_main.h:74
#3  0x0000fffff7c974cc in __libc_start_main_impl (main=0xaaaaaaaaad40 <main>, argc=1, argv=0xffffffffee98, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=<optimized out>) at ../csu/libc-start.c:392
#4  0x0000aaaaaaaab270 in _start ()

[slouken]

Good catch, thanks!