linux-kernel - Re: [RFC][PATCH] drm: kirin: Add a mutex to avoid fb initialization race

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Date:   Sat, 25 Feb 2017 09:22:02 +0800
From:   liuxinliang <z.liuxinliang@...ilicon.com>
To:     John Stultz <john.stultz@...aro.org>
CC:     lkml <linux-kernel@...r.kernel.org>,
        Rongrong Zou <zourongrong@...il.com>,
        Xinwei Kong <kong.kongxinwei@...ilicon.com>,
        Chen Feng <puck.chen@...ilicon.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sean Paul <seanpaul@...omium.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC][PATCH] drm: kirin: Add a mutex to avoid fb initialization
 race



On 2017/2/25 5:33, John Stultz wrote:
> On Thu, Feb 23, 2017 at 5:55 PM, liuxinliang
> <z.liuxinliang@...ilicon.com> wrote:
>> Hi John,
>>
>> On 2017/2/23 8:56, John Stultz wrote:
>>> In some cases I've been seeing a race where two framebuffers
>>> would be initialized, as kirin_fbdev_output_poll_changed()
>>> might get called quickly in succession, resulting in the fb
>>> initialization happening twice. This could cause the system
>>
>> I might understand this race. This because two places call
>> drm_helper_hpd_irq_event might cause the race:
>> One place is here
>> static int kirin_drm_kms_init(struct drm_device *dev)
>> {
>> ...
>>      /* force detection after connectors init */
>>      (void)drm_helper_hpd_irq_event(dev);
>> ...
>> }
>>
>> another is the adv7533 interrupt thread handler
>> static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)
>> {
>> ...
>>      if (process_hpd && irq0 & ADV7511_INT0_HPD && adv7511->bridge.encoder)
>>          drm_helper_hpd_irq_event(adv7511->connector.dev);
>> ...
>> }
>>
>> right?
>>
>> I don't get a better way to fix this yet , I like to put fb_lock into
>> kirin_drm_private.
> Ok. I've moved the mutex to the kirin_drm_private structure.
>
> Anything else you'd like to see before I resend?

Thanks, no more then.


Best,
-xinliang

>
> thanks
> -john
>
> .
>