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09:50]: > On Tue, Aug 26, 2025 at 09:37:22AM -0400, Liam R. Howlett wrote: > > I really don't think this is worth doing. We're avoiding a race between > > oom and a task unmap - the MMF bits should be used to avoid this race - > > or at least mitigate it. > > Yes for sure, as explored at length in previous discussions this feels like > we're papering over cracks here. > > _However_, I'm sort of ok with a minimalistic fix that solves the proximate > issue even if it is that, as long as it doesn't cause issues in doing so. > > So this is my take on the below and why I'm open to it! > > > > > They are probably both under the read lock, but considering how rare it > > would be, would a racy flag check be enough - it is hardly critical to > > get right. Either would reduce the probability. > > Zongjinji - I'm stil not sure that you've really indicated _why_ you're > seeing such a tight and unusual race. Presumably some truly massive number > of tasks being OOM'd and unmapping but... yeah that seems odd anyway. > > But again, if we can safely fix this in a way that doesn't hurt stuff too > much I'm ok with it (of course, these are famous last words in the kernel > often...!) > > Liam - are you open to a solution on the basis above, or do you feel we > ought simply to fix the underlying issue here? At least this is a benign race. I'd think using MMF_ to reduce the race would achieve the same goal with less risk - which is why I bring it up. Really, both methods should be low risk, so I'm fine with either way. But I am interested in hearing how this race is happening enough to necessitate a fix. Reversing the iterator is a one-spot fix - if this happens elsewhere then we're out of options. Using the MMF_ flags is more of a scalable fix, if it achieves the same results. > > to me we're at a simple enough implementaiton of this (esp. utilising the > helper you mention) that probably kthis is fine (like the meme, > or... hopefully not :) > > I will go with your judgment here! > > Cheers, Lorenzo