https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100352
--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
More complete backtrace using reproduction on command line:
...
Thread 1 "async_io_1.exe" received signal SIGSEGV, Segmentation fault.
__lll_unlock_elision (lock=0x6069d0, private=0)
at ../sysdeps/unix/sysv/linux/x86/elision-unlock.c:29
29 _xend();
(gdb) bt
#0 __lll_unlock_elision (lock=0x6069d0, private=0)
at ../sysdeps/unix/sysv/linux/x86/elision-unlock.c:29
#1 0x00007ffff7b64b03 in __gthread_mutex_unlock (__mutex=0x6069d0)
at ../libgcc/gthr-default.h:779
#2 0x00007ffff7b65e5c in _gfortrani_unlock_unit (u=0x6068f0)
at /home/vries/gcc_versions/devel/src/libgfortran/io/unit.c:772
#3 0x00007ffff7b6445e in _gfortran_st_write_done (dtp=0x7fffffffd5e0)
at /home/vries/gcc_versions/devel/src/libgfortran/io/transfer.c:4496
#4 0x000000000040116a in MAIN__ ()
#5 0x0000000000401af0 in main ()
...
OK, se we're hitting this case: unlocking a free lock:
...
(gdb) l
24 __lll_unlock_elision(int *lock, int private)
25 {
26 /* When the lock was free we're in a transaction.
27 When you crash here you unlocked a free lock. */
28 if (*lock == 0)
29 _xend();
30 else
31 lll_unlock ((*lock), private);
32 return 0;
33 }
...
