linux-kernel - Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc

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Date:	Mon, 28 Jan 2013 19:13:54 -0500
From:	Jason Cooper <jason@...edaemon.net>
To:	Soeren Moch <smoch@....de>, gennarone@...il.com, mchehab@...hat.com
Cc:	Andrew Lunn <andrew@...n.ch>, Arnd Bergmann <arnd@...db.de>,
	Greg KH <gregkh@...uxfoundation.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	linux-mm@...ck.org, Kyungmin Park <kyungmin.park@...sung.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linaro-mm-sig@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all
 dma_alloc_coherent() calls

On Mon, Jan 28, 2013 at 09:59:18PM +0100, Soeren Moch wrote:
> On 23.01.2013 19:10, Andrew Lunn wrote:
> >>>>
> >>>
> >>>Now (in the last hour) stable, occasionally lower numbers:
> >>>3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
> >>>3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
> >>>3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
> >>>3396 3396 3396 3396 3396 3396 3396 3396 3396 3365 3396 3394 3396 3396
> >>>3396 3396 3373 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
> >>>3396 3353 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396 3396
> >>>3394 3396 3396 3396 3396 3396 3396 3396
> >>>
> >>>Before the last pool exhaustion going down:
> >>>3395 3395 3389 3379 3379 3374 3367 3360 3352 3343 3343 3343 3342 3336
> >>>3332 3324 3318 3314 3310 3307 3305 3299 3290 3283 3279 3272 3266 3265
> >>>3247 3247 3247 3242 3236 3236
> >>>
> >>Here I stopped vdr (and so closed all dvb_demux devices), the number
> >>was remaining the same 3236, even after restart of vdr (and restart
> >>of streaming).
> >
> >So it does suggest a leak. Probably somewhere on an error path,
> >e.g. its lost video sync.
> >
> 
> Now I activated the debug messages in em28xx. From the messages I
> see no correlation of the pool exhaustion and lost sync. Also I
> cannot see any error messages from the em28xx driver.
> I see a lot of init_isoc/stop_urbs (maybe EPG scan?) without
> draining the coherent pool (checked with 'cat
> /debug/dma-api/num_free_entries', which gave stable numbers), but
> after half an hour there are only init_isoc messages without
> corresponding stop_urbs messages and num_free_entries decreased
> until coherent pool exhaustion.
> 
> Any idea where the memory leak is? What is allocating coherent
> buffers for orion-ehci?

Keeping in mind that I am completely unfamiliar with usb dvb, my best
guess is that the problem is in em28xx-core.c:1131

According to your log messages, it is in mode 2, which is
EM28XX_DIGITAL_MODE.

There seem to be good hints in

86d38d1e [media] em28xx: pre-allocate DVB isoc transfer buffers

I added the relevant parties to the To:...

For Gianluca and Mauro, the whole thread may be found at:

http://markmail.org/message/wm4wlgzoudixd4so#query:+page:1+mid:o7phz7cosmwpcsrz+state:results

thx,

Jason.

> 
>   Soeren
> 
> 
> Jan 28 20:46:03 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:03 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:46:03 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:03 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:46:23 guruvdr kernel: em28xx #0 em28xx_stop_urbs :em28xx:
> called em28xx_stop_urbs
> Jan 28 20:46:23 guruvdr kernel: em28xx #1 em28xx_stop_urbs :em28xx:
> called em28xx_stop_urbs
> Jan 28 20:46:24 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:24 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:46:24 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:24 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:46:44 guruvdr kernel: em28xx #1 em28xx_stop_urbs :em28xx:
> called em28xx_stop_urbs
> Jan 28 20:46:44 guruvdr kernel: em28xx #0 em28xx_stop_urbs :em28xx:
> called em28xx_stop_urbs
> Jan 28 20:46:45 guruvdr kernel: em28xx #1/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:45 guruvdr kernel: em28xx #1 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:46:45 guruvdr kernel: em28xx #0/2-dvb: Using 5 buffers
> each with 64 x 940 bytes
> Jan 28 20:46:45 guruvdr kernel: em28xx #0 em28xx_init_isoc :em28xx:
> called em28xx_init_isoc in mode 2
> Jan 28 20:54:33 guruvdr kernel: ERROR: 1024 KiB atomic DMA coherent
> pool is too small!
> Jan 28 20:54:33 guruvdr kernel: Please increase it with
> coherent_pool= kernel parameter!
> 
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