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

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Message-ID: <20151113090115.1ad4235b@gandalf.local.home>
Date:	Fri, 13 Nov 2015 09:01:15 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	yalin wang <yalin.wang2010@...il.com>
Cc:	Vlastimil Babka <vbabka@...e.cz>, Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ebru Akagunduz <ebru.akagunduz@...il.com>,
	Rik van Riel <riel@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	jmarchan@...hat.com, mgorman@...hsingularity.net,
	willy@...ux.intel.com, linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org
Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread

On Fri, 13 Nov 2015 19:54:11 +0800
yalin wang <yalin.wang2010@...il.com> 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



> ok ,  i will send V5 patch .
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