On Tue, 2019-05-28 at 22:51 -0700, Rick Edgecombe wrote: > The addition of VM_FLUSH_RESET_PERMS for BPF JIT allocations was > bisected to prevent boot on an UltraSparc III machine. It was found > that > sometime shortly after the TLB flush this flag does on vfree of the > BPF > program, the machine hung. Further investigation showed that before > any of > the changes for this flag were introduced, with > CONFIG_DEBUG_PAGEALLOC > configured (which does a similar TLB flush of the vmalloc range on > every vfree), this machine also hung shortly after the first vmalloc > unmap/free. > > So the evidence points to there being some existing issue with the > vmalloc TLB flushes, but it's still unknown exactly why these hangs > are > happening on sparc. It is also unknown when someone with this > hardware > could resolve this, and in the meantime using this flag on it turns a > lurking behavior into something that prevents boot. The sparc TLB flush issue has been bisected and is being worked on now, so hopefully we won't need this patch: https://marc.info/?l=linux-sparc&m=155915694304118&w=2
