On 5/21/21 1:48 PM, Josh Poimboeuf wrote: > On Fri, May 21, 2021 at 06:53:18PM +0100, Mark Brown wrote: >> On Fri, May 21, 2021 at 12:47:13PM -0500, Madhavan T. Venkataraman wrote: >>> On 5/21/21 12:42 PM, Mark Brown wrote: >> >>>> 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()? >> >> I think it's fine to leave it as it is. > > Either way works for me, but if you remove those 'reliable = false' > statements for stack corruption then, IIRC, the caller would still have > some confusion between the end of stack error (-ENOENT) and the other > errors (-EINVAL). > I will leave it the way it is. That is, I will do reliable = false on errors like you suggested. > So the caller would have to know that -ENOENT really means success. > Which, to me, seems kind of flaky. > Actually, that is why -ENOENT was introduced - to indicate successful stack trace termination. A return value of 0 is for continuing with the stack trace. A non-zero value is for terminating the stack trace. So, either we return a positive value (say 1) to indicate successful termination. Or, we return -ENOENT to say no more stack frames left. I guess -ENOENT was chosen. > BTW, not sure if you've seen what we do in x86, but we have a > 'frame->error' which gets set for an error, and which is cumulative > across frames. So non-fatal reliable-type errors don't necessarily have > to stop the unwind. The end result is the same as your patch, but it > seems less confusing to me because the 'error' is cumulative. But that > might be personal preference and I'd defer to the arm64 folks. > OK. I will wait to see if any arm64 folks have an opinion on this. I am fine with any approach. Madhavan
