On Thu 2020-06-18 16:55:19, John Ogness wrote: > Replace the existing ringbuffer usage and implementation with > lockless ringbuffer usage. Even though the new ringbuffer does not > require locking, all existing locking is left in place. Therefore, > this change is purely replacing the underlining ringbuffer. > > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -2009,9 +2056,9 @@ asmlinkage int vprintk_emit(int facility, int level, > > /* This stops the holder of console_sem just where we want him */ > logbuf_lock_irqsave(flags); > - curr_log_seq = log_next_seq; > + pending_output = !prb_read_valid(prb, console_seq, NULL); > printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args); > - pending_output = (curr_log_seq != log_next_seq); > + pending_output &= prb_read_valid(prb, console_seq, NULL); This will stop working after we remove the locks. Consoles will be able to handle messages while the new one is being added. There will be no gurantee that someone is still hadling the previously pending output. Please, always handle consoles when printed_len is not zero!!! The pending output was just an optimization added recently. Nobody requested it. It was just an idea that made sense. This new code is a ticking bomb. It is far from obvious that it _must_ get removed after we remove the lock. And it will be hard to debug why the consoles are sometimes not handled. > logbuf_unlock_irqrestore(flags); > > /* If called from the scheduler, we can not call up(). */ Best Regards, Petr _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
