On Thu, 11 Aug 2016 10:46:53 +0200 (CEST) Miroslav Benes <mbe...@suse.cz> wrote:
> On Tue, 9 Aug 2016, Steven Rostedt wrote: > > > On Tue, 9 Aug 2016 10:16:00 +0200 (CEST) > > Miroslav Benes <mbe...@suse.cz> wrote: > > > > > > > I agree it is kind of shooting oneself in the foot bug, because explicit > > > call to a sleeping function may not be the brightest thing to do. However > > > I see two (closely related) issues with this. > > > > > > 1. It is a change in behaviour. Ftrace silently relies on an atomicity of > > > ops->func(). I don't see it documented anywhere, but it did not matter > > > because the atomicity was always guaranteed as described above. Now there > > > is a possibility to achieve a situation which breaks the assumption. It > > > makes me worried. > > > > Why? It's something that a kernel developer should be aware of. I mean, > > that ops->func can easily be called from *any* context, like irq, > > softirq, or even an NMI. One who hooks into any function of the kernel > > should understand that it has special requirements, just like we don't > > document that you can't sleep in an NMI. > > > > And if you only hook to functions that can sleep, then great! You are > > allowed to do that too. Just like calling a module function that can > > sleep. You need to make sure nothing is calling your function when you > > unload the module. I don't see anything that is deceptive here. > > At least the comment in ftrace_shutdown() is deceptive. Which comment? It may require an update to be less "deceptive". -- Steve > > But well, I understood your opinion from the first reply. I just didn't > agree with it and that's why I expressed it. >
