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

From: Vlastimil Babka
Date: Mon Nov 16 2015 - 05:16:31 EST


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


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/