On Sat 2018-01-13 16:31:00, Sergey Senozhatsky wrote: > On (01/12/18 13:55), Petr Mladek wrote: > [..] > > > I'm not fixing console_unlock(), I'm fixing printk(). BTW, all my > > > kernels are CONFIG_PREEMPT (I'm a RT guy), my mind thinks more about > > > PREEMPT kernels than !PREEMPT ones. > > > > I would say that the patch improves also console_unlock() but only in > > non-preemttive context. > > > > By other words, it makes console_unlock() finite in preemptible context > > (limited by buffer size). It might still be unlimited in > > non-preemtible context. > > could you elaborate a bit? Ah, I am sorry, I swapped the conditions. I meant that console_unlock() is finite in non-preemptible context. There are two possibilities if console_unlock() is in atomic context and never sleeps. First, if there are new printk() callers, they could take over the job. Second. if they are no more callers, the current owner will release the lock after processing the existing messages. In both situations, the current owner will not handle more than the entire buffer. Therefore it is limited. We might argue if it is enough. But the point is that it is limited which is a step forward. And I think that you already agreed that this was a step forward. The chance of taking over the lock is lower when console_unlock() owner could sleep. But then there is not a danger of a softlockup. In each case, this patch did not make it worse. Could we agree on this, please? All in all, this patch improved one scenario and did not make worse another one. We know that it does not fix everything. But it is a step forward. Could we agree on this, please? Best Regards, Petr -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
