Memory leak in I2C (ticket #1898)

Mark Studebaker mds at mds.gotdns.com
Sat Feb 19 18:39:04 CET 2005


were there any hints in dmesg?
hitting table size limits in i2c-core can also return ENOMEM, but
should also generate a message about increasing I2C_xxx_MAX.
I'd say this is more likely than running your whole box out of memory.
mds

James Olin Oden wrote:
> On Tue, 15 Feb 2005 12:06:15 +0100 (CET), Jean Delvare
> <khali at linux-fr.org> wrote:
> 
>>Hi James,
>>
>>I am moving this to the mailing-list since it is likely to require some
>>investigation before we can find out what's going on, and our current
>>ticket system is not meant for this. (Philip, Axel, where is the new
>>Bugzilla system going?)
>>
> 
> Fine by me.
>  
> 
>>Most things in the i2c core in linux 2.4 are static, so I doubt that
>>there can be a leak in i2c-core itself. i2c-proc OTOH is likely to
>>allocate memory for various things, so this is a candidate. And, as you
>>suggested yourself, individual drivers are candidates as well.
>>
>>Please tell us:
>>
>>* Which i2c drivers you are using.
>>
> 
> Here is the list in the order they are loaded:
> 
>     i2c-core i2c-dev i2c-proc i2c-i801 lm87b lm93 eeprom pcf8574
> 
> When I found the appearant memory leak I was only loading and
> unloading modules lm93, eeprom, pcf8574.
> 
> 
>>* What your test script is. Which modules are you cycling exactly, in
>>which order, at which rate? I'd be happy to do the same on my own
>>machines (with different bus and chip drivers) and see if I can
>>reproduce the problem.
> 
> I have attached the script.   As far as rate, I was trying to force an
> oops (which I could do with a previous release) so the only throttling
> was system itself.  Basically I ran the test sc ript with this shell
> snippet:
> 
>     while test.i2c.oops
>     do
>          :
>     done
> 
> As I said earlier in the bug report, its not a likely scenario, but
> IMHO it is a valid test case, if only if it stresses the registration
> deregistration process.   On the system I was running this on we have
> a program that kicks off about every 30 seconds and  runs the sensors
> command.  I don't think you needed that to produce the memory leak,
> but it probably was requried to produce the oops that you guys seemed
> to have fixed.
> 
> The test script is fairly simple.  It has an internal list of modules
> that it loads in one order, and then unloads in the opposite order. 
> You can pass the arg --modcount=$number to tell it starting from the
> back only load and unload $number modules.   You can override its
> default module list by using --modules=$mod1,...,$modN.   I use depmod
> to load and unload the modules, if dependent modules are not loaded
> they should be loaded (not tested that though).
> 
> 
>>Once we know in which kernel module the leak is, it shouldn't be too
>>hard to find out where the leak is exactly. There aren't that many
>>memory allocations in there.
>>
>>BTW, thanks a lot for reporting.
> 
> Not a problem.  Thanks for looking into this.  One of these days I'll
> get my head around the I2C and lm_sensors architecture in the kernel,
> and maybe I can send you patches instead (-;
> 
> Cheers...james




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