On Mon, 22 May 2023, Linus Torvalds wrote: > On Mon, May 22, 2023 at 11:39 AM David Rientjes <rientjes@xxxxxxxxxx> wrote: > > > > I think VM_BUG_ON*() and friends are used to crash the kernel for > > debugging so that we get a crash dump and because some variants don't > > exist for VM_WARN_ON(). > > I do think that from a VM developer standpoint, I think it should be > fine to just effectively turn VM_BUG_ON() into WARN_ON_ONCE() together > with panic_on_warn. > > Maybe we could even extend 'panic_on_warn' to be a bitmap and > effectively have a "don't panic on non-VM warnings" option. > I hadn't thought of that approach, it would definitely help us achieve our goal of emitting warnings on a small set of production hosts that we don't want to crash. It's also very clean. Right now kernel.panic_on_warn can either be 0 or 1. We can keep the lowest bit to be "panic on all warnings" and then bit-1 as "panic on debug VM warnings." When CONFIG_DEBUG_VM is enabled, set the new bit by default so there's no behavior change. Then, we can keep VM_BUG_ON*() and friends around and extend them to check whether they should BUG() after the WARN_ON(1) or not. On our production hosts, we'll just set kernel.panic_on_oom to 0. I'll give it a few days to see if anybody else has any comments or concerns; if not, I'll send a v2 based on this.
