Re: omap3isp cache error when unloading

[Michael Jones <michael.jones@matrix-vision.de>]

On 03/02/2011 08:18 PM, Laurent Pinchart wrote:
> Hi Michael,
> 
> On Tuesday 01 March 2011 17:41:01 Michael Jones wrote:
>> Hi all,
>>
>> I get a warning about a cache error with the following steps:
>>
>> 0. load omap3-isp
>> 1. set up media broken media pipeline. (e.g. set different formats on
>> opposite ends of a link, as will be the case for using the lane shifter)
>> 2. try to capture images.  isp_video_streamon() returns -EPIPE from the
>> failed isp_video_validate_pipeline() call.
>> 3. unload omap3-isp module
>>
>> then I get the following from kmem_cache_destroy():
>>
>> slab error in kmem_cache_destroy(): cache `iovm_area_cache': Can't free all
>> objects [<c0040318>] (unwind_backtrace+0x0/0xec) from [<c00bfe14>]
>> (kmem_cache_destroy+0x88/0xf4) [<c00bfe14>] (kmem_cache_destroy+0x88/0xf4)
>> from [<c00861f8>] (sys_delete_module+0x1c4/0x230) [<c00861f8>]
>> (sys_delete_module+0x1c4/0x230) from [<c003b680>]
>> (ret_fast_syscall+0x0/0x30)
>>
>> Then, when reloading the module:
>> SLAB: cache with size 32 has lost its name
>>
>> Can somebody else confirm that they also observe this behavior?
> 
> I can't reproduce that (tried both 2.6.32 and 2.6.37). Could you give me some 
> more details about your exact test procedure (such as how you configure the 
> pipeline) ?
> 

Sorry, I should've mentioned: I'm using your media-0005-omap3isp branch
based on 2.6.38-rc5.  I didn't have the problem with 2.6.37, either.
It's actually not related to mis-configuring the ISP pipeline like I
thought at first- it also happens after I have successfully captured images.

I've since tracked down the problem, although I don't understand the
cache management well enough to be sure it's a proper fix, so hopefully
some new recipients on this can make suggestions/comments.

The patch below solves the problem, which modifies a commit by Fernando
Guzman Lugo from December.

-Michael

>From db35fb8edca2a4f8fd37197d77fd58676cb1dcac Mon Sep 17 00:00:00 2001
From: Michael Jones <michael.jones@matrix-vision.de>
Date: Thu, 3 Mar 2011 16:50:39 +0100
Subject: [PATCH] fix iovmm slab cache error on module unload

modify "OMAP: iommu: create new api to set valid da range"

This modifies commit c7f4ab26e3bcdaeb3e19ec658e3ad9092f1a6ceb.
---
 arch/arm/plat-omap/iovmm.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/arm/plat-omap/iovmm.c b/arch/arm/plat-omap/iovmm.c
index 6dc1296..2fba6f1 100644
--- a/arch/arm/plat-omap/iovmm.c
+++ b/arch/arm/plat-omap/iovmm.c
@@ -280,7 +280,10 @@ static struct iovm_struct *alloc_iovm_area(struct iommu *obj, u32 da,
 	alignement = PAGE_SIZE;
 
 	if (flags & IOVMF_DA_ANON) {
-		start = obj->da_start;
+		/*
+		 * Reserve the first page for NULL
+		 */
+		start = obj->da_start + PAGE_SIZE;
 
 		if (flags & IOVMF_LINEAR)
 			alignement = iopgsz_max(bytes);
-- 
1.7.4.1



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