Messages in this thread | | | Date | Tue, 22 Feb 2022 10:37:05 +0200 | Subject | Re: [PATCH v3 9/9] drm/tegra: Support context isolation | From | Mikko Perttunen <> |
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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
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