On Wed, Apr 14, 2021 at 05:23:38AM -0500, Madhavan T. Venkataraman wrote: > On 4/13/21 6:02 AM, Mark Brown wrote: > > On Mon, Apr 12, 2021 at 02:55:35PM -0500, Madhavan T. Venkataraman wrote:
> >> 3. We are going to assume that the reliable unwinder is only for livepatch > >> purposes > >> and will only be invoked on a task that is not currently running. The > >> task either > > > > The reliable unwinder can also be invoked on itself. > I have not called out the self-directed case because I am assuming that the > reliable unwinder > is only used for livepatch. So, AFAICT, this is applicable to the task that > performs the > livepatch operation itself. In this case, there should be no unreliable > functions on the > self-directed stack trace (otherwise, livepatching would always fail). Someone might've added a probe of some kind which upsets things so there's a possibility things might fail. Like you say there's no way a system in such a state can succesfully apply a live patch but we might still run into that situation. > >> I suggest we do (3) first. Then, review the assembly functions to do (1). > >> Then, review the > >> remaining ones to see which ones must be blacklisted, if any. > > I'm not clear what the concrete steps you're planning to do first are > > there - your 3 seems like a statement of assumptions. For flagging > > functions I do think it'd be safer to default to assuming that all > > SYM_CODE functions can't be unwound reliably rather than only explicitly > > listing ones that cause problems. > They are not assumptions. They are true statements. But I probably did not do > a good > job of explaining. But Josh sent out a patch that updates the documentation > that > explains what I said a lot better. You say true statements, I say assumptions :)
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