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

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Date:   Thu, 5 Nov 2020 22:54:29 +0530
From:   Deepak R Varma <mh12gx2825@...il.com>
To:     Felix Kuehling <felix.kuehling@....com>
Cc:     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 Wed, Nov 04, 2020 at 03:01:17PM -0500, Felix Kuehling wrote:
> 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.

Hello Felix,
You are correct. There are calls made to idr_alloc with start range from
0. So, for this driver, id=0 seems a valid use case. The change I
proposed is not relevant for this driver. You may please ignore the
patch.

Thank you,
./drv

> 
> 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;