Re: [PATCH V4] mm: fix kernel crash in khugepaged thread

[Vlastimil Babka]

On 11/16/2015 02:35 AM, yalin wang wrote:
> > On Nov 13, 2015, at 22:01, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> >
> > On Fri, 13 Nov 2015 19:54:11 +0800
> > yalin wang <yalin.wang2010@xxxxxxxxx> wrote:
> >
> > > > > > 	TP_fast_assign(
> > > > > > 		__entry->mm = mm;
> > > > > > -		__entry->pfn = pfn;
> > > > > > +		__entry->pfn = page_to_pfn(page);
> > > > >
> > > > > Instead of the condition, we could have:
> > > > >
> > > > > 	__entry->pfn = page ? page_to_pfn(page) : -1;
> > > >
> > > > I agree. Please do it like this.
> >
> > hmm, pfn is defined as an unsigned long, would -1 be the best.
> > Or should it be (-1UL).
> >
> > Then we could also have:
> >
> >         TP_printk("mm=%p, scan_pfn=0x%lx%s, writable=%d, referenced=%d, none_or_zero=%d, status=%s, unmapped=%d",
> >                 __entry->mm,
> >                 __entry->pfn == (-1UL) ? 0 : __entry->pfn,
> > 		__entry->pfn == (-1UL) ? "(null)" : "",
> >
> > Note the added %s after %lx I have in the print format.
> >
> > -- Steve
> it is not easy to print for perf tools in userspace ,
> if you use this format ,
> for user space perf tool, it print the entry by look up the member in entry struct by offset ,
> you print a dynamic string which user space perf tool donât know how to print this string .

Does it work through trace-cmd?

> Thanks

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