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Date: Tue, 22 Jun 2010 12:24:30 +0530 From: Sankar P <sankar.curiosity@...il.com> To: Catalin Marinas <catalin.marinas@....com> Cc: "Luis R. Rodriguez" <lrodriguez@...eros.com>, rnagarajan@...ell.com, teheo@...ell.com, Pekka Enberg <penberg@...helsinki.fi>, Luis Rodriguez <Luis.Rodriguez@...eros.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: Probable Bug (or configuration error) in kmemleak On Fri, Jun 18, 2010 at 6:55 PM, Sankar P <sankar.curiosity@...il.com> wrote: > On Fri, Jun 18, 2010 at 6:30 PM, Catalin Marinas > <catalin.marinas@....com> wrote: >> On Fri, 2010-06-18 at 09:11 +0100, Sankar P wrote: >>> On Thu, Jun 17, 2010 at 11:06 PM, Luis R. Rodriguez >>> <lrodriguez@...eros.com> wrote: >>> > On Thu, Jun 17, 2010 at 02:21:56AM -0700, Sankar P wrote: >>> >> Hi, >>> >> >>> >> I wanted to detect memory leaks in one of my kernel modules. So I >>> >> built Linus' tree with the following config options enabled (on top >>> >> of make defconfig) >>> >> >>> >> CONFIG_DEBUG_KMEMLEAK=y >>> >> CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=400 >>> >> CONFIG_DEBUG_KMEMLEAK_TEST=y >>> >> >>> >> If I boot with this kernel, debugfs is automatically mounted. But I do >>> >> not have the file: >>> >> >>> >> /sys/kernel/debug/kmemleak >>> >> >>> >> created at all. There are other files like kprobes in the mounted >>> >> /sys/kernel/debug directory btw. So I am not able to detect any of the >>> >> memory leaks. Is there anything I am doing wrong or missing (or) is >>> >> this a bug in kmemleak ? >>> >> >>> >> Please let me know your suggestions to fix this and get memory leaks >>> >> reporting working. Thanks. >>> >> >>> >> The full .config file is also attached with this mail. Sorry for the >>> >> attachment, I did not want to paste 5k lines in the mail. Sorry if it >>> >> is wrong. >>> > >>> > >>> > This is odd.. Do you see this message on your kernel ring buffer? >>> > >>> > Failed to create the debugfs kmemleak file >>> > >>> >>> I dont see such an error in the dmesg output. But I got another >>> interesting error: >>> >>> [ 0.000000] kmemleak: Early log buffer exceeded, please increase >>> DEBUG_KMEMLEAK_EARLY_LOG_SIZE >>> [ 0.000000] kmemleak: Kernel memory leak detector disabled >> >> You would need to increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE. The default of >> 400 seems ok for me but it may not work with some other kernel >> configurations (that's a static array for logging memory allocations >> before the kmemleak is fully initialised and can start tracking them). >> >>> But after that also, I see some other lines like: >>> >>> [ 0.511641] kmemleak: vmalloc(64) = f7857000 >>> [ 0.511645] kmemleak: vmalloc(64) = f785a000 >> >> This is because you compiler the test module into the kernel >> (DEBUG_KMEMLEAK_TEST). It's not kmemleak printing this but it's testing >> module (which leaks memory on purpose). >> >>> The variable DEBUG_KMEMLEAK_EARLY_LOG_SIZE was set to 400 by default. >>> I changed it to 4000 and then 40000 (may be should try < 32567 ?) but >>> still I get the same error message and the file >>> /sys/kernel/debug/kmem* is never created at all. >> >> This shouldn't usually happen with values greater than 2000. From your >> kernel log, the version seems to be 2.6.32. Do you have the same >> problems with 2.6.35-rc3? >> >> Your .config seems to refer to the 2.6.35-rc3 kernel - are you checking >> the right image? >> > > Ah sorry. I am testing by ssh into a remote machine. After installing > my kernel (after increasing the DEBUG_KMEMLEAK_EARLY_LOG_SIZE), Before > rebooting, I forgot to change the default-kernel this time. I will > check once again and will let you know. Thank you a lot for the > "dmesg" pointer. > > Thanks for your "dmesg" pointer, I was able to solve the problem. I found that whenever I ran "defconfig", the value of 400 for DEBUG_KMEMLEAK_EARLY_LOG_SIZE seem to be inadequate always. So I made a trivial patch incrementing the value to 1000. This worked fine for my debugging. So, take the patch I will send next, if you prefer. -- Sankar P http://psankar.blogspot.com -- 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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