Re: [REGRESSION] Errors at reboot after 722e5f2b1eec

From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: James Wang <jnwang@suse.com>, Takashi Iwai <tiwai@suse.de>
Cc: Borislav Petkov <bp@suse.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	linux-kernel@vger.kernel.org, Pingfan Liu <kernelfans@gmail.com>
Subject: Re: [REGRESSION] Errors at reboot after 722e5f2b1eec
Date: Thu, 13 Sep 2018 16:13:08 +0200	[thread overview]
Message-ID: <2551848.SakgYeHO72@aspire.rjw.lan> (raw)
In-Reply-To: <8d9cf4b9-4c52-2e1d-6778-312c7a2fdffe@suse.com>

On Thursday, September 13, 2018 12:03:36 PM CEST James Wang wrote:
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> On 09/11/2018 02:15 PM, Takashi Iwai wrote:
> > On Tue, 11 Sep 2018 14:11:30 +0200,
> > James Wang wrote:
> >> I did try it from kernel : head
> > OK, then the bug is present with 4.19-rc2, at least.
> > Please check my test kernel later (it's still being built).
> Hi folks,  I attach two log about 4.19-rc3 and 4.19-rc3+Rafeal suggestion.

OK, no difference AFAICS.

This means that the commit turned up by bisection simply uncovered an existing
ordering issue, apparently between an IOMMU and its client (ie. it appears that
the client is shut down after the IOMMU).

This isn't limited to shutdown and you'd see the same issue on system-wide
suspend/resume (in fact, the Pingfan Liu's patches make shutdown use the
same device list that is used for system-wide PM).

One way to mitigate such issues is to add a device link between the two
devices in question to enforce the correct suspend/resume/shutdown ordering
between them.

Thanks,
Rafael