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Date: Fri, 28 Dec 2012 01:33:12 +0100 From: Zlatko Calusic <zlatko.calusic@...on.hr> To: sedat.dilek@...il.com CC: LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org> Subject: Re: BUG: unable to handle kernel NULL pointer dereference at 0000000000000500 On 28.12.2012 01:24, Sedat Dilek wrote: > On Fri, Dec 28, 2012 at 12:51 AM, Zlatko Calusic > <zlatko.calusic@...on.hr> wrote: >> On 28.12.2012 00:42, Sedat Dilek wrote: >>> >>> On Fri, Dec 28, 2012 at 12:39 AM, Zlatko Calusic >>> <zlatko.calusic@...on.hr> wrote: >>>> >>>> On 28.12.2012 00:30, Sedat Dilek wrote: >>>>> >>>>> >>>>> Hi Zlatko, >>>>> >>>>> I am not sure if I hit the same problem as described in this thread. >>>>> >>>>> Under heavy load, while building a customized toolchain for the Freetz >>>>> router project I got a BUG || NULL pointer derefence || kswapd || >>>>> zone_balanced || pgdat_balanced() etc. (details see my screenshot). >>>>> >>>>> I will try your patch from [1] ***only*** on top of my last >>>>> Linux-v3.8-rc1 GIT setup (post-v3.8-rc1 mainline + some net-fixes). >>>>> >>>> >>>> Yes, that's the same bug. It should be fixed with my latest patch, so I'd >>>> appreciate you testing it, to be on the safe side this time. There should >>>> be >>>> no difference if you apply it to anything newer than 3.8-rc1, so go for >>>> it. >>>> Thanks! >>>> >>> >>> Not sure how I can really reproduce this bug as one build worked fine >>> within my last v3.8-rc1 kernel. >>> I increased the parallel-make-jobs-number from "4" to "8" to stress a >>> bit harder. >>> Just building right now... and will report. >>> >>> If you have any test-case (script or whatever), please let me/us know. >>> >> >> Unfortunately not, I haven't reproduced it yet on my machines. But it seems >> that bug will hit only under heavy memory pressure. When close to OOM, or >> possibly with lots of writing to disk. It's also possible that fragmentation >> of memory zones could provoke it, that means testing it for a longer time. >> > > I tested successfully by doing simultaneously... > - building Freetz with 8 parallel make-jobs > - building Linux GIT with 1 make-job > - 9 tabs open in firefox > - In one tab I ran YouTube music video > - etc. > > I am reading [1] and [2] where another user reports success by reverting this... > > commit cda73a10eb3f493871ed39f468db50a65ebeddce > "mm: do not sleep in balance_pgdat if there's no i/o congestion" > > BTW, this machine has also 4GiB RAM (Ubuntu/precise AMD64). > > Feel free to add a "Reported-by/Tested-by" if you think this is a > positive report. > Thanks for the testing! And keep running it in case something interesting pops up. ;) No need to revert cda73a10eb because it fixes another bug. And the patch you're now running fixes the new bug I introduced with a combination of my latest 2 patches. Nah, it gets complicated... :) But, at least I found the culprit and as soon as Linus applies the fix, everything will be hunky dory again, at least on this front. :P Thanks, -- Zlatko -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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