On Mon, Jul 06, 2020 at 09:40:12PM +0200, Peter Zijlstra wrote: > On Mon, Jul 06, 2020 at 11:39:33AM -0700, Paul E. McKenney wrote: > > On Mon, Jul 06, 2020 at 08:29:26PM +0200, Peter Zijlstra wrote: > > > On Mon, Jul 06, 2020 at 09:26:33AM -0700, Paul E. McKenney wrote: > > > > If they do not consider their Linux OS running correctly :-) > > > > Many of them really do not care at all. In fact, some would consider > > Linux failing to run as an added bonus. > > This I think is why we have compiler people in the thread that care a > lot more. Here is hoping! ;-) > > > > Nevertheless, yes, control dependencies also need attention. > > > > > > Today I added one more \o/ > > > > Just make sure you continually check to make sure that compilers > > don't break it, along with the others you have added. ;-) > > There's: > > kernel/locking/mcs_spinlock.h: smp_cond_load_acquire(l, VAL); \ > kernel/sched/core.c: smp_cond_load_acquire(&p->on_cpu, !VAL); > kernel/smp.c: smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); > > arch/x86/kernel/alternative.c: atomic_cond_read_acquire(&desc.refs, !VAL); > kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); > kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); > kernel/locking/qrwlock.c: atomic_cond_read_acquire(&lock->cnts, VAL == _QW_WAITING); > kernel/locking/qspinlock.c: atomic_cond_read_acquire(&lock->val, !(VAL & _Q_LOCKED_MASK)); > kernel/locking/qspinlock.c: val = atomic_cond_read_acquire(&lock->val, !(VAL & _Q_LOCKED_PENDING_MASK)); > > include/linux/refcount.h: smp_acquire__after_ctrl_dep(); > ipc/mqueue.c: smp_acquire__after_ctrl_dep(); > ipc/msg.c: smp_acquire__after_ctrl_dep(); > ipc/sem.c: smp_acquire__after_ctrl_dep(); > kernel/locking/rwsem.c: smp_acquire__after_ctrl_dep(); > kernel/sched/core.c: smp_acquire__after_ctrl_dep(); > > kernel/events/ring_buffer.c:__perf_output_begin() > > And I'm fairly sure I'm forgetting some... One could argue there's too > many of them to check already. > > Both GCC and CLANG had better think about it. That would be good! I won't list the number of address/data dependencies given that there are well over a thousand of them. Thanx, Paul
