This uses atomic operations to access lock elision metadata that is accessed
concurrently (ie, adapt_count fields). The size of the data is less than a
word but accessed only with atomic loads and stores.
See also x86 commit ca6e601a9d4a72b3699cca15bad12ac1716bf49a:
"Use C11-like atomics instead of plain memory accesses in x86 lock elision."
ChangeLog:
* sysdeps/unix/sysv/linux/s390/elision-lock.c
(__lll_lock_elision): Use atomics to load / store adapt_count.
* sysdeps/unix/sysv/linux/s390/elision-trylock.c
(__lll_trylock_elision): Likewise.
c813dae5d8