linux-kernel - Re: [PATCH v2] driver core: Partially revert "driver core: correct device's shutdown order"

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Message-ID: <20180710125956.GA25343@kroah.com>
Date:   Tue, 10 Jul 2018 14:59:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Pingfan Liu <kernelfans@...il.com>, linux-kernel@...r.kernel.org,
        Grygorii Strashko <grygorii.strashko@...com>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Dave Young <dyoung@...hat.com>, linux-pci@...r.kernel.org,
        Lukas Wunner <lukas@...ner.de>,
        Linux PM <linux-pm@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [PATCH v2] driver core: Partially revert "driver core: correct
 device's shutdown order"

On Tue, Jul 10, 2018 at 02:51:33PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 52cdbdd49853 (driver core: correct device's shutdown order)
> introduced a regression by breaking device shutdown on some systems.
> 
> Namely, the devices_kset_move_last() call in really_probe() added by
> that commit is a mistake as it may cause parents to follow children
> in the devices_kset list which then causes shutdown to fail.  For
> example, if a device has children before really_probe() is called
> for it (which is not uncommon), that call will cause it to be
> reordered after the children in the devices_kset list and the
> ordering of that list will not reflect the correct device shutdown
> order any more.
> 
> Also it causes the devices_kset list to be constantly reordered
> until all drivers have been probed which is totally pointless
> overhead in the majority of cases and it only covered an issue
> with system shutdown, while system-wide suspend/resume potentially
> had the same issue on the affected platforms (which was not covered).
> 
> Moreover, the shutdown issue originally addressed by the change in
> really_probe() made by commit 52cdbdd49853 is not present in 4.18-rc
> any more, since dra7 started to use the sdhci-omap driver which
> doesn't disable any regulators during shutdown, so the really_probe()
> part of commit 52cdbdd49853 can be safely reverted.  [The original
> issue was related to the omap_hsmmc driver used by dra7 previously.]
> 
> For the above reasons, revert the really_probe() modifications made
> by commit 52cdbdd49853.
> 
> The other code changes made by commit 52cdbdd49853 are useful and
> they need not be reverted.
> 
> Fixes: 52cdbdd49853 (driver core: correct device's shutdown order)
> Link: https://lore.kernel.org/lkml/CAFgQCTt7VfqM=UyCnvNFxrSw8Z6cUtAi3HUwR4_xPAc03SgHjQ@mail.gmail.com/
> Reported-by: Pingfan Liu <kernelfans@...il.com>
> Tested-by: Pingfan Liu <kernelfans@...il.com>
> Reviewed-by: Kishon Vijay Abraham I <kishon@...com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> -> v2: Added information from Kishon on the fact that it should be safe
>        to revert the really_probe() modifications added by the
>        problematic commit.  Also added the Reviewed-by tag from Kishon.

Looks good to me, want me to queue it up in my tree, or are you going to
send it on to Linus?

And shouldn't this have a stable tag as well?

thanks,

greg k-h