On 5/21/21 12:42 PM, Mark Brown wrote: > On Fri, May 21, 2021 at 12:23:52PM -0500, Madhavan T. Venkataraman wrote: >> On 5/21/21 11:11 AM, Mark Brown wrote: >>> On Sat, May 15, 2021 at 11:00:17PM -0500, madvenka@xxxxxxxxxxxxxxxxxxx wrote: > >>>> + frame->reliable = true; > >>> All these checks are good checks but as you say there's more stuff that >>> we need to add (like your patch 2 here) so I'm slightly nervous about > >> OK. So how about changing the field from a flag to an enum that says exactly >> what happened with the frame? > > TBH I think the code is fine, or rather will be fine when it gets as far > as actually being used - this was more a comment about when we flip this > switch. > OK. >> Also, the caller can get an exact idea of why the stack trace failed. > > I'm not sure anything other than someone debugging things will care > enough to get the code out and then decode it so it seems like it'd be > more trouble than it's worth, we're unlikely to be logging the code as > standard. > OK. >>> The other thing I guess is the question of if we want to bother flagging >>> frames as unrelaible when we return an error; I don't see an issue with >>> it and it may turn out to make it easier to do something in the future >>> so I'm fine with that > >> Initially, I thought that there is no need to flag it for errors. But Josh >> had a comment that the stack trace is indeed unreliable on errors. Again, the >> word unreliable is the one causing the problem. > > My understanding there is that arch_stack_walk_reliable() should be > returning an error if either the unwinder detected an error or if any > frame in the stack is flagged as unreliable so from the point of view of > users it's just looking at the error code, it's more that there's no > need for arch_stack_walk_reliable() to consider the reliability > information if an error has been detected and nothing else looks at the > reliability information. > > Like I say we may come up with some use for the flag in error cases in > future so I'm not opposed to keeping the accounting there. > So, should I leave it the way it is now? Or should I not set reliable = false for errors? Which one do you prefer? Josh, Are you OK with not flagging reliable = false for errors in unwind_frame()? Madhavan
