Subject: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls

From: [email-masked] (Soeren Moch)
Date: Mon, 28 Jan 2013 21:59:18 +0100

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?

   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!