Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 30 Oct 2023 18:12:51 -1000 | Subject | Re: [GIT PULL] RCU changes for v6.7 |
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On Fri, 27 Oct 2023 at 01:33, Frederic Weisbecker <frederic@kernel.org> 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.
Linus
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