linux-kernel - Re: [PATCH] drm/amdkfd: replace idr_init() by idr_init

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Message-ID: <91ebae30-c75c-5485-8de5-36464e97ed7e@amd.com>
Date:   Wed, 4 Nov 2020 15:01:17 -0500
From:   Felix Kuehling <felix.kuehling@....com>
To:     Deepak R Varma <mh12gx2825@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amdkfd: replace idr_init() by idr_init_base()

On 2020-11-04 10:13 a.m., Deepak R Varma wrote:
> idr_init() uses base 0 which is an invalid identifier. The new function
> idr_init_base allows IDR to set the ID lookup from base 1. This avoids
> all lookups that otherwise starts from 0 since 0 is always unused.

I disagree. We call idr_alloc with start=0 for both these IDRs. That 
means 0 seems to be a valid handle.

Regards,
   Felix


>
> References: commit 6ce711f27500 ("idr: Make 1-based IDRs more efficient")
>
> Signed-off-by: Deepak R Varma <mh12gx2825@...il.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_events.c  | 2 +-
>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> index ba2c2ce0c55a..b3339b53c8ad 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> @@ -230,7 +230,7 @@ static int create_other_event(struct kfd_process *p, struct kfd_event *ev)
>   void kfd_event_init_process(struct kfd_process *p)
>   {
>   	mutex_init(&p->event_mutex);
> -	idr_init(&p->event_idr);
> +	idr_init_base(&p->event_idr, 1);
>   	p->signal_page = NULL;
>   	p->signal_event_count = 0;
>   }
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index 65803e153a22..022e61babe30 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -1289,7 +1289,7 @@ struct kfd_process_device *kfd_create_process_device_data(struct kfd_dev *dev,
>   	list_add(&pdd->per_device_list, &p->per_device_data);
>   
>   	/* Init idr used for memory handle translation */
> -	idr_init(&pdd->alloc_idr);
> +	idr_init_base(&pdd->alloc_idr, 1);
>   
>   	return pdd;
>