From: Steven Price <steven.price@arm.com>
To: Chunyou Tang <tangchunyou@163.com>
Cc: tomeu.vizoso@collabora.com, airlied@linux.ie,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
alyssa.rosenzweig@collabora.com,
ChunyouTang <tangchunyou@icubecorp.cn>
Subject: Re: [PATCH] drm/panfrost:modify 'break' to 'continue' to traverse the circulation
Date: Mon, 21 Jun 2021 11:45:18 +0100 [thread overview]
Message-ID: <eb036b84-ebb7-1f2d-3abd-7de13479fa3c@arm.com> (raw)
In-Reply-To: <20210619110923.00001c64@163.com>
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On 19/06/2021 04:09, Chunyou Tang wrote:
> Hi Steve,
> 1,
> from
> https://lore.kernel.org/lkml/31644881-134a-2d6e-dddf-e658a3a8176b@arm.com/
> I can see what your sent,I used a wrong email address,Now it correct.
> 2,
>>> Unless I'm mistaken the situation where some mappings may be NULL is
>>> caused by the loop in panfrost_lookup_bos() not completing
>>> successfully
>>> (panfrost_gem_mapping_get() returning NULL). In this case if
>>> mappings[i]
>>> is NULL then all following mappings must also be NULL. So 'break'
>>> allows
>>> us to skip the later ones. Admittedly the performance here isn't
>>> important so I'm not sure it's worth the optimisation, but AIUI this
>>> code isn't actually wrong.
>
> from panfrost_lookup_bos(),you can see:
> for (i = 0; i < job->bo_count; i++) {
> struct panfrost_gem_mapping *mapping;
>
> bo = to_panfrost_bo(job->bos[i]);
> ICUBE_DEBUG_PRINTK("panfrost bo gem handle=0x%x
> is_dumb=%d\n", bo->gem_handle, bo->is_dumb);
> if (!bo->is_dumb) {
> mapping = panfrost_gem_mapping_get(bo, priv);
> if (!mapping) {
> ret = -EINVAL;
> break;
> }
>
> atomic_inc(&bo->gpu_usecount);
> job->mappings[i] = mapping;
> } else {
> atomic_inc(&bo->gpu_usecount);
> job->mappings[i] = NULL;
> }
> }
This code isn't upstream - in drm-misc/drm-misc-next (and all mainline
kernels from what I can tell) this doesn't have any "is_dumb" test.
Which branch are you using?
> if bo->is_dumb is TRUE,the job->mappings[i] will set to NULL,and the
> while will be continue,so if job->mappings[i] is NULL,the following
> can not be NULL.
I agree that with the above code the panfrost_job_cleanup() would need
changing. But we don't (currently) have this code upstream, so this
change doesn't make sense upstream.
Thanks,
Steve
> 3,
> I've had this problem in our project,the value of is_dumb like these:
> 0
> 0
> 0
> 1
> 0
> 0
> 0
> so,when job->mappings[i] is NULL,we can not break the while in
> panfrost_job_cleanup().
>
> thanks
> Chunyou
>
> ÓÚ Fri, 18 Jun 2021 13:43:25 +0100
> Steven Price <steven.price@arm.com> дµÀ:
>
>> On 17/06/2021 09:04, ChunyouTang wrote:
>>> From: ChunyouTang <tangchunyou@icubecorp.cn>
>>>
>>> The 'break' can cause 'Memory manager not clean during takedown'
>>>
>>> It cannot use break to finish the circulation,it should use
>>>
>>> continue to traverse the circulation.it should put every mapping
>>>
>>> which is not NULL.
>>
>> You don't appear to have answered my question about whether you've
>> actually seen this happen (and ideally what circumstances). In my
>> previous email[1] I explained why I don't think this is needed. You
>> need to convince me that I've overlooked something.
>>
>> Thanks,
>>
>> Steve
>>
>> [1]
>> https://lore.kernel.org/r/31644881-134a-2d6e-dddf-e658a3a8176b%40arm.com
>>
>>> Signed-off-by: ChunyouTang <tangchunyou@icubecorp.cn>
>>> ---
>>> drivers/gpu/drm/panfrost/panfrost_job.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c
>>> b/drivers/gpu/drm/panfrost/panfrost_job.c index
>>> 6003cfeb1322..52bccc1d2d42 100644 ---
>>> a/drivers/gpu/drm/panfrost/panfrost_job.c +++
>>> b/drivers/gpu/drm/panfrost/panfrost_job.c @@ -281,7 +281,7 @@
>>> static void panfrost_job_cleanup(struct kref *ref) if
>>> (job->mappings) { for (i = 0; i < job->bo_count; i++) {
>>> if (!job->mappings[i])
>>> - break;
>>> + continue;
>>>
>>> atomic_dec(&job->mappings[i]->obj->gpu_usecount);
>>> panfrost_gem_mapping_put(job->mappings[i]);
>>>
>
>
next prev parent reply other threads:[~2021-06-21 10:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 8:04 [PATCH] drm/panfrost:modify 'break' to 'continue' to traverse the circulation ChunyouTang
2021-06-18 12:43 ` Steven Price
2021-06-19 3:09 ` Chunyou Tang
2021-06-21 10:45 ` Steven Price [this message]
2021-06-22 1:31 ` Chunyou Tang
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