On 2021/02/12 22:12, Michal Hocko wrote: > On Fri 12-02-21 21:58:15, Tetsuo Handa wrote: >> On 2021/02/12 21:30, Michal Hocko wrote: >>> On Fri 12-02-21 12:22:07, Matthew Wilcox wrote: >>>> On Fri, Feb 12, 2021 at 08:18:11PM +0900, Tetsuo Handa wrote: >>>>> On 2021/02/12 1:41, Michal Hocko wrote: >>>>>> But I suspect we have drifted away from the original issue. I thought >>>>>> that a simple check would help us narrow down this particular case and >>>>>> somebody messing up from the IRQ context didn't sound like a completely >>>>>> off. >>>>>> >>>>> >>>>> From my experience at https://lkml.kernel.org/r/201409192053.IHJ35462.JLOMOSOFFVtQFH@xxxxxxxxxxxxxxxxxxx , >>>>> I think we can replace direct PF_* manipulation with macros which do not receive "struct task_struct *" argument. >>>>> Since TASK_PFA_TEST()/TASK_PFA_SET()/TASK_PFA_CLEAR() are for manipulating PFA_* flags on a remote thread, we can >>>>> define similar ones for manipulating PF_* flags on current thread. Then, auditing dangerous users becomes easier. >>>> >>>> No, nobody is manipulating another task's GFP flags. >>> >>> Agreed. And nobody should be manipulating PF flags on remote tasks >>> either. >>> >> >> No. You are misunderstanding. The bug report above is an example of manipulating PF flags on remote tasks. > > Could you be more specific? I do not remember there was any theory that > somebody is manipulating flags on a remote task. A very vague theory was > that an interrupt context might be doing that on the _current_ context > but even that is not based on any real evidence. It is a pure > speculation. > Please read the link above. The report is an example of manipulating PF flags on a remote task. You are thinking interrupt context as the only possible culprit, but you should also think concurrent access as the other possible culprit.
