On Mon, Oct 30, 2023 at 06:12:51PM -1000, Linus Torvalds wrote: > On Fri, 27 Oct 2023 at 01:33, Frederic Weisbecker <frederic@xxxxxxxxxx> wrote: > > > > rcu/stall: Stall detection updates. Introduce RCU CPU Stall notifiers > > that allows a subsystem to provide informations to help debugging. > > Also cure some false positive stalls. > > I absolutely detest this stall notifier thing. > > Putting the stall notifier before the stall message does not "help > debugging". Quite the reverse. It ends up being a lovely way to make > sure that the debug message is never printed, because there's some > entirely untested - and thus buggy - notifier on the chain before the > printout from the actual stall code. > > I've pulled this, but I really want to voice my objection against > these kinds of "debugging aids". I have personally spent way too many > hours debugging a dead machine because some "debug aid" ended up being > untested garbage. > > If you absolutely think that this is a worthy and useful thing to do, > then at the very least make sure that these "debug aids" will always > come *after* the core output, and can't make things horrendously > worse. > > But in general, think twice before adding "maybe somebody else wants > to print debug info". Because unless you have a really really REALLY > good reason for it, it's more likely to hurt than to help. > > Right now I see no users of this except for the rcu torture code, and > it certainly doesn't seem hugely important there. And so I'm wondering > what the actual real use-case would be. I see, one possibility is to revert this and switch to normal calls for any future debug information to add from another subsystem. I'll wait for Paul's opinion... Thanks.
