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References: <20220712042258.293010-1-jstultz@google.com> <13c5ca05-a366-2751-4f26-d978d074f748@amd.com>
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From:   John Stultz <jstultz@google.com>
Date:   Tue, 12 Jul 2022 08:48:07 -0700
Message-ID: <CANDhNCp_d2M+n90T1ziP5rHF85ZsxyN6qg4iE84ucPO-XK_HUg@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/3] drm: drm_syncobj: Add note in DOC about absolute
 timeout values
To:     =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Lionel Landwerlin <lionel.g.landwerlin@intel.com>,
        Chunming Zhou <david1.zhou@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel@lists.freedesktop.org
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On Tue, Jul 12, 2022 at 12:40 AM Christian K=C3=B6nig
<christian.koenig@amd.com> wrote:
> Am 12.07.22 um 06:22 schrieb John Stultz:
> > After having to debug down through the kernel to figure out
> > why my _WAIT calls were always timing out, I realized its
> > an absolute timeout value instead of the more common relative
> > timeouts.
> >
> > This detail should be called out in the documentation, as while
> > the absolute value makes sense here, its not as common for timeout
> > values.
>
> Well absolute timeout values are mandatory for making -ERESTARTSYS work
> without any additional handling.

Yes! I'm not saying it's wrong to use absolute values, just that
relative values are common enough to create some confusion here.

> So using them is recommended for ~20 years now and IIRC even documented
> somewhere.

So in addition to "somewhere", why not in the interface documentation as we=
ll?

> See here as well https://lwn.net/Articles/17744/ how much trouble system
> calls with relative timeouts are.

Yep. Well aware. :)

thanks
-john