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

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Message-ID: <0ab001d11def$081c80d0$18558270$@alibaba-inc.com>
Date:	Fri, 13 Nov 2015 16:41:03 +0800
From:	"Hillf Danton" <hillf.zj@...baba-inc.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"'yalin wang'" <yalin.wang2010@...il.com>,
	"Ingo Molnar" <mingo@...hat.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Rik van Riel" <riel@...hat.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	"Vlastimil Babka" <vbabka@...e.cz>, "Mel Gorman" <mgorman@...e.de>,
	"linux-kernel" <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH V4] mm: fix kernel crash in khugepaged thread

> 
> Instead of the condition, we could have:
> 
> 	__entry->pfn = page ? page_to_pfn(page) : -1;
> 
> 
> But if there's no reason to do the tracepoint if page is NULL, then
> this patch is fine. I'm just throwing out this idea.
> 
we trace only if page is valid

--- linux-next/mm/huge_memory.c	Fri Nov 13 16:00:22 2015
+++ b/mm/huge_memory.c	Fri Nov 13 16:26:19 2015
@@ -1987,7 +1987,8 @@ static int __collapse_huge_page_isolate(
 
 out:
 	release_pte_pages(pte, _pte);
-	trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
+	if (page)
+		trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
 					    referenced, writable, result);
 	return 0;
 }
--



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