18.02.2022 14:39, Mikko Perttunen пишет:
> + if (context->memory_context && context->client->ops->get_streamid_offset) {
^^^
> + int offset = context->client->ops->get_streamid_offset(context->client);
> +
> + if (offset >= 0) {
> + job->context = context->memory_context;
> + job->engine_streamid_offset = offset;
> + host1x_context_get(job->context);
> + }
You should bump refcount unconditionally or you'll get refcnt underflow
on put, when offset < 0.
> + }
> +
> /*
> * job_data is now part of job reference counting, so don't release
> * it from here.
> diff --git a/drivers/gpu/drm/tegra/uapi.c b/drivers/gpu/drm/tegra/uapi.c
> index 9ab9179d2026..be33da54d12c 100644
> --- a/drivers/gpu/drm/tegra/uapi.c
> +++ b/drivers/gpu/drm/tegra/uapi.c
> @@ -33,6 +33,9 @@ static void tegra_drm_channel_context_close(struct tegra_drm_context *context)
> struct tegra_drm_mapping *mapping;
> unsigned long id;
>
> + if (context->memory_context)
> + host1x_context_put(context->memory_context);
The "if (context->memory_context &&
context->client->ops->get_streamid_offset)" above doesn't match the "if
(context->memory_context)". You'll get refcount underflow.
On 2/19/22 20:35, Dmitry Osipenko wrote:
> 18.02.2022 14:39, Mikko Perttunen пишет:
>> + if (context->memory_context && context->client->ops->get_streamid_offset) {
> ^^^
>> + int offset = context->client->ops->get_streamid_offset(context->client);
>> +
>> + if (offset >= 0) {
>> + job->context = context->memory_context;
>> + job->engine_streamid_offset = offset;
>> + host1x_context_get(job->context);
>> + }
>
> You should bump refcount unconditionally or you'll get refcnt underflow
> on put, when offset < 0.
This refcount is intended to be dropped from 'release_job', where it's
dropped if job->context is set, which it is from this path.
>
>> + }
>> +
>> /*
>> * job_data is now part of job reference counting, so don't release
>> * it from here.
>> diff --git a/drivers/gpu/drm/tegra/uapi.c b/drivers/gpu/drm/tegra/uapi.c
>> index 9ab9179d2026..be33da54d12c 100644
>> --- a/drivers/gpu/drm/tegra/uapi.c
>> +++ b/drivers/gpu/drm/tegra/uapi.c
>> @@ -33,6 +33,9 @@ static void tegra_drm_channel_context_close(struct tegra_drm_context *context)
>> struct tegra_drm_mapping *mapping;
>> unsigned long id;
>>
>> + if (context->memory_context)
>> + host1x_context_put(context->memory_context);
>
> The "if (context->memory_context &&
> context->client->ops->get_streamid_offset)" above doesn't match the "if
> (context->memory_context)". You'll get refcount underflow.
And this drop is for the refcount implicitly added when allocating the
memory context through host1x_context_alloc; so these two places should
be independent.
Please elaborate if I missed something.
Thanks,
Mikko
21.02.2022 15:06, Mikko Perttunen пишет:
> On 2/19/22 20:35, Dmitry Osipenko wrote:
>> 18.02.2022 14:39, Mikko Perttunen пишет:
>>> + if (context->memory_context &&
>>> context->client->ops->get_streamid_offset) {
>> ^^^
>>> + int offset =
>>> context->client->ops->get_streamid_offset(context->client);
>>> +
>>> + if (offset >= 0) {
>>> + job->context = context->memory_context;
>>> + job->engine_streamid_offset = offset;
>>> + host1x_context_get(job->context);
>>> + }
>>
>> You should bump refcount unconditionally or you'll get refcnt underflow
>> on put, when offset < 0.
>
> This refcount is intended to be dropped from 'release_job', where it's
> dropped if job->context is set, which it is from this path.
>
>>
>>> + }
>>> +
>>> /*
>>> * job_data is now part of job reference counting, so don't
>>> release
>>> * it from here.
>>> diff --git a/drivers/gpu/drm/tegra/uapi.c b/drivers/gpu/drm/tegra/uapi.c
>>> index 9ab9179d2026..be33da54d12c 100644
>>> --- a/drivers/gpu/drm/tegra/uapi.c
>>> +++ b/drivers/gpu/drm/tegra/uapi.c
>>> @@ -33,6 +33,9 @@ static void tegra_drm_channel_context_close(struct
>>> tegra_drm_context *context)
>>> struct tegra_drm_mapping *mapping;
>>> unsigned long id;
>>> + if (context->memory_context)
>>> + host1x_context_put(context->memory_context);
>>
>> The "if (context->memory_context &&
>> context->client->ops->get_streamid_offset)" above doesn't match the "if
>> (context->memory_context)". You'll get refcount underflow.
>
> And this drop is for the refcount implicitly added when allocating the
> memory context through host1x_context_alloc; so these two places should
> be independent.
>
> Please elaborate if I missed something.
You named context as memory_context and then have
context=context->memory_context. Please try to improve the variable
names, like drm_ctx->host1x_ctx for example.
I'm also not a big fan of the "if (ref) put(ref)" pattern. Won't be
better to move all the "if (!NULL)" checks inside of get()/put() and
make the invocations unconditional?
On 2/21/22 22:02, Dmitry Osipenko wrote:
> 21.02.2022 15:06, Mikko Perttunen пишет:
>> On 2/19/22 20:35, Dmitry Osipenko wrote:
>>> 18.02.2022 14:39, Mikko Perttunen пишет:
>>>> + if (context->memory_context &&
>>>> context->client->ops->get_streamid_offset) {
>>> ^^^
>>>> + int offset =
>>>> context->client->ops->get_streamid_offset(context->client);
>>>> +
>>>> + if (offset >= 0) {
>>>> + job->context = context->memory_context;
>>>> + job->engine_streamid_offset = offset;
>>>> + host1x_context_get(job->context);
>>>> + }
>>>
>>> You should bump refcount unconditionally or you'll get refcnt underflow
>>> on put, when offset < 0.
>>
>> This refcount is intended to be dropped from 'release_job', where it's
>> dropped if job->context is set, which it is from this path.
>>
>>>
>>>> + }
>>>> +
>>>> /*
>>>> * job_data is now part of job reference counting, so don't
>>>> release
>>>> * it from here.
>>>> diff --git a/drivers/gpu/drm/tegra/uapi.c b/drivers/gpu/drm/tegra/uapi.c
>>>> index 9ab9179d2026..be33da54d12c 100644
>>>> --- a/drivers/gpu/drm/tegra/uapi.c
>>>> +++ b/drivers/gpu/drm/tegra/uapi.c
>>>> @@ -33,6 +33,9 @@ static void tegra_drm_channel_context_close(struct
>>>> tegra_drm_context *context)
>>>> struct tegra_drm_mapping *mapping;
>>>> unsigned long id;
>>>> + if (context->memory_context)
>>>> + host1x_context_put(context->memory_context);
>>>
>>> The "if (context->memory_context &&
>>> context->client->ops->get_streamid_offset)" above doesn't match the "if
>>> (context->memory_context)". You'll get refcount underflow.
>>
>> And this drop is for the refcount implicitly added when allocating the
>> memory context through host1x_context_alloc; so these two places should
>> be independent.
>>
>> Please elaborate if I missed something.
>
> You named context as memory_context and then have
> context=context->memory_context. Please try to improve the variable
> names, like drm_ctx->host1x_ctx for example.
>
> I'm also not a big fan of the "if (ref) put(ref)" pattern. Won't be
> better to move all the "if (!NULL)" checks inside of get()/put() and
> make the invocations unconditional?
I agree that the naming here is confusing with different kinds of
contexts flying around, though I would prefer not to change the original
'struct tegra_drm_context *context' since it's used all around the code.
But I'll try to make it clearer.
Regarding moving NULL checks inside get/put, I personally dislike that
pattern (also with e.g. kfree) since when reading the code, it makes it
more difficult to see that the pointer can be NULL.
Mikko