Date: Mon, 27 Jul 2015 23:40:36 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: What's left for 1.1.11 release? This release cycle has gotten way behind-schedule and I'd like to wrap it up in the next few days. The CFI generation patch is the last actual feature/roadmap item I want to get committed still, but I believe there may be some important bugs to try to fix first. In particular: - Deadlocks in malloc due to a_store lacking acquire barrier on x86. - Unbounded VSZ growth under free contention. In principle the a_store issue affects all libc-internal __lock/LOCK uses, and stdio locks too, but it's only been observed in malloc. Since there don't seem to be any performance-relevant uses of a_store that don't actually need the proper barrier, I think we have to just put an explicit barrier (lock orl $0,(%esp) or mfence) after the store and live with the loss of performance. Our x86 a_barrier is also "wrong" for the same reasons as a_store, but I don't think any of its callers actually want the full strength of a barrier, just some (much weaker) ordering guarantees. This should be revisited after release to assess what properties the callers actually want. The VSZ growth issue is much harder to address before a release. I would not be comfortable with pushing the changes needed for a proper fix without a long testing window before a release, and even then I'm not eagar to write this code. "Big hammer" solutions are of course possible (e.g. serializing all malloc operations with a big lock) but undesirable. The best I can probably do is put together an optional patch which affected users can try until a real fix is available. I'm also aware of the following open issues with patch discussion going on, but they're not bugs/regressions affecting existing users, and I don't see us reaching a resolution within a short timeframe: - Adding powerpc soft-float. - ARM asm incompatibility withe clang. Anything else I'm missing in the way of bug reports of pending patches that need to be addressed? Rich
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