Messages in this thread | | | Date | Thu, 3 Dec 2015 15:09:26 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: ftrace: stop using kstop_machine to enable/disable tracing |
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On Thu, Dec 03, 2015 at 10:05:25AM -0500, Steven Rostedt wrote: > On Thu, 3 Dec 2015 09:38:21 +0000 > Will Deacon <will.deacon@arm.com> wrote: > > I think you're missing the case where the instruction changes under our > > feet after we've read it but before we've replaced it (e.g. due to module > > unloading). I think that's why ftrace_modify_code has the comment about > > lack of locking thanks to stop_machine. > > Note, ftrace has a module notifier that is called when a module is > being unloaded and before the text goes away. This code grabs the > ftrace_lock mutex and removes the module functions from the ftrace > list, such that it will no longer do any modifications to that module's > text. > > The update to make functions be traced is done under the ftrace_lock > mutex as well. > > You do not need to worry about module text disappearing from > underneath you while you do your modifications.
Good.
> Now, if there's comments that suggest otherwise, they need to be > updated.
Yeah, I think the comments on x86 and arm64 are out of date. They also mention the freeing of __init sections -- is that still a concern?
Will
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