diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/s390/elision-trylock.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/s390/elision-trylock.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/sysdeps/unix/sysv/linux/s390/elision-trylock.c b/sysdeps/unix/sysv/linux/s390/elision-trylock.c index 3d5a994..a3252b8 100644 --- a/sysdeps/unix/sysv/linux/s390/elision-trylock.c +++ b/sysdeps/unix/sysv/linux/s390/elision-trylock.c @@ -49,8 +49,10 @@ __lll_trylock_elision (int *futex, short *adapt_count) __builtin_tabort (_HTM_FIRST_USER_ABORT_CODE | 1); } - /* Only try a transaction if it's worth it. */ - if (*adapt_count <= 0) + /* Only try a transaction if it's worth it. See __lll_lock_elision for + why we need atomic accesses. Relaxed MO is sufficient because this is + just a hint. */ + if (atomic_load_relaxed (adapt_count) <= 0) { unsigned status; @@ -65,9 +67,10 @@ __lll_trylock_elision (int *futex, short *adapt_count) __builtin_tend (); /* Note: Changing the adapt_count here might abort a transaction on a different cpu, but that could happen anyway when the futex is - acquired, so there's no need to check the nesting depth here. */ + acquired, so there's no need to check the nesting depth here. + See above for why relaxed MO is sufficient. */ if (aconf.skip_lock_busy > 0) - *adapt_count = aconf.skip_lock_busy; + atomic_store_relaxed (adapt_count, aconf.skip_lock_busy); } else { @@ -87,7 +90,8 @@ __lll_trylock_elision (int *futex, short *adapt_count) { /* Lost updates are possible, but harmless. Due to races this might lead to *adapt_count becoming less than zero. */ - (*adapt_count)--; + atomic_store_relaxed (adapt_count, + atomic_load_relaxed (adapt_count) - 1); } return lll_trylock (*futex); |