On Fri 15-09-17 23:12:24, Tetsuo Handa wrote: > Michal Hocko wrote: > > On Fri 15-09-17 21:09:29, Tetsuo Handa wrote: > > > Michal Hocko wrote: > > > > On Fri 15-09-17 20:38:49, Tetsuo Handa wrote: > > > > [...] > > > > > You said "identify _why_ we see the lockup trigerring in the first > > > > > place" without providing means to identify it. Unless you provide > > > > > means to identify it (in a form which can be immediately and easily > > > > > backported to 4.9 kernels; that is, backporting not-yet-accepted > > > > > printk() offloading patchset is not a choice), this patch cannot be > > > > > refused. > > > > > > > > I fail to see why. It simply workarounds an existing problem elsewhere > > > > in the kernel without deeper understanding on where the problem is. You > > > > can add your own instrumentation to debug and describe the problem. This > > > > is no different to any other kernel bugs... > > > > > > Please do show us your patch for that. Normal users cannot afford developing > > > such instrumentation to debug and describe the problem. > > > > Stop this nonsense already! Any kernel bug/lockup needs a debugging > > which might be non-trivial and it is necessary to understand the real > > culprit. We do not add random hacks to silence a problem. We aim at > > fixing it! > > Assuming that Wang Yu's trace has > > RIP: 0010:[<...>] [<...>] dump_stack+0x.../0x... > > line in the omitted part (like Cong Wang's trace did), I suspect that a thread > which is holding dump_lock is unable to leave console_unlock() from printk() for > so long because many other threads are trying to call printk() from warn_alloc() > while consuming all CPU time. __dump_stack should be an atomic context AFAIR. But as we already discussed some time ago this lock is not fair and one function might bounce for too long. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
