On Wed, Feb 17, 2016 at 10:28:29AM +0100, Ingo Molnar wrote: > > * Byungchul Park <[email protected]> wrote: > > > diff --git a/kernel/locking/semaphore.c b/kernel/locking/semaphore.c > > index b8120ab..6634b68 100644 > > --- a/kernel/locking/semaphore.c > > +++ b/kernel/locking/semaphore.c > > @@ -130,13 +130,14 @@ EXPORT_SYMBOL(down_killable); > > int down_trylock(struct semaphore *sem) > > { > > unsigned long flags; > > - int count; > > + int count = -1; > > > > - raw_spin_lock_irqsave(&sem->lock, flags); > > - count = sem->count - 1; > > - if (likely(count >= 0)) > > - sem->count = count; > > - raw_spin_unlock_irqrestore(&sem->lock, flags); > > + if (raw_spin_trylock_irqsave(&sem->lock, flags)) { > > + count = sem->count - 1; > > + if (likely(count >= 0)) > > + sem->count = count; > > + raw_spin_unlock_irqrestore(&sem->lock, flags); > > + } > > I still don't really like it: two parallel trylocks will cause one of them to > fail > - while with the previous code they would both succeed. > > None of these changes are necessary with all the printk robustification > changes/enhancements we talked about, right?
Right. I expect that Jan's patch which Sergey informed can make printk robuster. Actually I'm waiting for the patch done. And I thought that it's also a problem that a trylock implementation can make a system deadlock. Don't you think it need to make a trylock only either acquire or fail in any case? IMHO, waiting something within trylock is wrong. I'm just curious. Thanks, Byungchul > > Thanks, > > Ingo
