On Tue, Jul 14, 2015 at 01:01:12PM -0500, Eric W. Biederman wrote: > Vivek Goyal <vgoyal@xxxxxxxxxx> writes: > > > On Tue, Jul 14, 2015 at 05:29:53PM +0000, dwalker@xxxxxxxxxx wrote: > > > > [..] > >> > >> > If a machine is failing, there are high chance it can't deliver you the > >> > >> > notification. Detecting that failure suing some kind of polling mechanism > >> > >> > might be more reliable. And it will make even kdump mechanism more > >> > >> > reliable so that it does not have to run panic notifiers after the crash. > >> > >> > >> > >> I think what your suggesting is that my company should change how it's hardware works > >> > >> and that's not really an option for me. This isn't a simple thing like checking over the > >> > >> network if the machine is down or not, this is way more complex hardware design. > >> > > > >> > > That means you are ready to live with an unreliable design. There might be > >> > > cases where notifier does not get run properly and you will not do switch > >> > > despite the fact that OS has failed. I was just trying to nudge you in > >> > > a direction which could be more reliable mechanism. > >> > > >> > Sigh I see some deep confusion going on here. > >> > > >> > The panic notifiers are just that panic notifiers. They have not been > >> > nor should they be tied to kexec. If those notifiers force a switch > >> > over of between machines I fail to see why you would care if it was > >> > kexec or another panic situation that is forcing that switchover. > >> > >> Hidehiro isn't fixing the failover situation on my side, he's fixing register > >> information collection when crash_kexec_post_notifiers is used. > > > > Sure. Given that we have created this new parameter, let us fix it so that > > we can capture the other cpu register state in crash dump. > > > > I am little disappointed that it was not tested well when this parameter was > > introuced. We should have atleast tested it to the extent to see if there > > is proper cpu state present for all cpus in the crash dump. > > > > At that point of time it looked like a simple modification > > to allow panic notifiers before crash_kexec(). > > Either that or we say no one cares enough, and it known broken so let's > just revert the fool thing. Masami, you introduced this option. Are you fine with the revert? Is it really being used and tested? > I honestly can't see how to support panic notifiers, before kexec. > There is no way to tell what is being done and all of the pieces > including smp_send_stop are known to be buggy. we should be able to replace smp_send_stop() with what crash_kexec() is doing to stop the machine? If yes, then it should be fine I guess. This parameter description clearly says that specify it at your own risk. So we are not issuing a big support statement for successful kdump after panic notifiers. If it is something fixable, otherwise user needs to deal with it. Thanks Vivek
