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From: Jason Gunthorpe <jgg@nvidia.com>
To: Christoph Hellwig <hch@lst.de>
Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org,
	David Airlie <airlied@linux.ie>,
	dri-devel@lists.freedesktop.org,
	Kirti Wankhede <kwankhede@nvidia.com>,
	linux-s390@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Halil Pasic <pasic@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	intel-gfx@lists.freedesktop.org,
	Jason Herne <jjherne@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH 04/10] driver core: Don't return EPROBE_DEFER to userspace during sysfs bind
Date: Mon, 14 Jun 2021 19:43:01 -0300	[thread overview]
Message-ID: <20210614224301.GO1002214@nvidia.com> (raw)
In-Reply-To: <20210614150846.4111871-5-hch@lst.de>

On Mon, Jun 14, 2021 at 05:08:40PM +0200, Christoph Hellwig wrote:

> @@ -679,8 +666,6 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>  		dev->pm_domain->dismiss(dev);
>  	pm_runtime_reinit(dev);
>  	dev_pm_set_driver_flags(dev, 0);
> -	if (probe_ret == -EPROBE_DEFER)
> -		driver_deferred_probe_add_trigger(dev, local_trigger_count);
>  done:

I like the new arrangement - however I'm looking at the ordering
relative to this:

>  	atomic_dec(&probe_count);
>  	wake_up_all(&probe_waitqueue);

And wondering if the idea is that driver_deferred_probe_add_trigger()
is supposed to be enclosed by the atomic, so that the
device_block_probing() / wait_for_device_probe() sequence is actually
a fence against queuing new work?

Which is suggesting that the other driver_deferred_probe_add_trigger()
at the top of really_probe is already ordered wrong?

Although, if that is the idea the wait_for_device_probe() doesn't look
entirely sequenced right..

It looks easy enough to fix by moving the probe_count up:

> +static int driver_probe_device(struct device_driver *drv, struct device *dev)
> +{
> +	int trigger_count = atomic_read(&deferred_trigger_count);
> +	int ret;
> +
> +	ret = __driver_probe_device(drv, dev);
> +	if (ret == -EPROBE_DEFER || ret == EPROBE_DEFER) {
> +		driver_deferred_probe_add(dev);
> +
> +		/*
> +		 * Did a trigger occur while probing? Need to re-trigger if yes
> +		 */
> +		if (trigger_count != atomic_read(&deferred_trigger_count) &&
> +		    !defer_all_probes)
> +			driver_deferred_probe_trigger();
> +	}

into here?

I didn't see a reason why it couldn't enclose the pm stuff too..

Jason

       reply	other threads:[~2021-06-14 22:43 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210614150846.4111871-1-hch@lst.de>
     [not found] ` <20210614150846.4111871-5-hch@lst.de>
2021-06-14 22:43   ` Jason Gunthorpe [this message]
     [not found] ` <20210614150846.4111871-2-hch@lst.de>
2021-06-15  5:16   ` [PATCH 01/10] driver core: Pull required checks into driver_probe_device() Greg Kroah-Hartman
2021-06-15 10:27   ` Cornelia Huck
     [not found] ` <20210614150846.4111871-3-hch@lst.de>
2021-06-14 18:47   ` [PATCH 02/10] driver core: Better distinguish probe errors in really_probe Kirti Wankhede
2021-06-15  5:17   ` Greg Kroah-Hartman
2021-06-15  5:21 ` Allow mdev drivers to directly create the vfio_device (v2 / alternative) Greg Kroah-Hartman
     [not found]   ` <20210615055021.GB21080@lst.de>
2021-06-15 15:27     ` Jason Gunthorpe
     [not found] ` <20210614150846.4111871-4-hch@lst.de>
2021-06-15  5:18   ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Greg Kroah-Hartman
2021-06-15 10:31   ` Cornelia Huck
     [not found] ` <20210614150846.4111871-6-hch@lst.de>
2021-06-15  5:20   ` [PATCH 05/10] driver core: Export device_driver_attach() Greg Kroah-Hartman
2021-06-15 10:49   ` Cornelia Huck
     [not found] ` <20210614150846.4111871-7-hch@lst.de>
2021-06-15 10:50   ` [PATCH 06/10] vfio/mdev: Remove CONFIG_VFIO_MDEV_DEVICE Cornelia Huck
     [not found] ` <20210614150846.4111871-8-hch@lst.de>
2021-06-15 10:54   ` [PATCH 07/10] vfio/mdev: Allow the mdev_parent_ops to specify the device driver to bind Cornelia Huck
     [not found] <20210615133519.754763-1-hch@lst.de>
     [not found] ` <20210615133519.754763-5-hch@lst.de>
2021-06-15 14:03   ` [PATCH 04/10] driver core: Don't return EPROBE_DEFER to userspace during sysfs bind Cornelia Huck
2021-06-15 19:36   ` Alex Williamson

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