linux-kernel - Re: [PATCH] drm/vmwgfx: Replace schedule() with schedule

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Message-ID: <CAKPKb8_tHVEFrkWHF3ycuDXOCJ9-qr64_sii9O4bcUiu4uuvRQ@mail.gmail.com>
Date: Tue, 28 Oct 2025 16:36:12 +0530
From: opensource india <opensource206@...il.com>
To: Zack Rusin <zack.rusin@...adcom.com>
Cc: maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, 
	airlied@...il.com, simona@...ll.ch, bcm-kernel-feedback-list@...adcom.com, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vmwgfx: Replace schedule() with schedule_hrtimeout()
 in fallback wait

Hi Zack Rusin,

On Mon, Oct 20, 2025 at 9:48 AM Zack Rusin <zack.rusin@...adcom.com> wrote:
>

> I don't remember exactly the schedule family of functions but isn't
> schedule_hrtimeout leaving the task in a running state? In general it
> looks like with the patch the task's current state doesn't match what
> was expected, plus I'm not sure if I quite get why the uninterruptible
> non-lazy case is being replaced with a lazy wait of NSEC_PER_MSEC's.
> It'd be great if you could explain a little bit better what you're
> doing here because the commit message is missing an explanation for
> either of those.
>
> z

Thank you for checking the patch.

The existing code does not specify any fixed wait time during the
fence wait. It simply invokes schedule(),
which means the task can be rescheduled immediately to check the fence
status again.

By using the high-resolution timer family of functions, we can specify
an explicit sleep duration.
In this patch, the sleep time is set to 1 ms, ensuring that the fence
status is checked at fixed 1 ms intervals.

This approach allows the CPU to be released to other tasks for a
deterministic period,
thereby reducing unnecessary CPU wakeups while maintaining timely
fence checks(FIXME expected the same).