linux-kernel - Re: [RFC PATCH v1 1/3] mm: teach mm by current context info to not do I/O during memory allocation

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Message-ID: <CACVXFVPXp8bK+A8xTZBWP5n43+S9qHQUg1VhiFVj9q7q+JfX8g@mail.gmail.com>
Date:	Wed, 17 Oct 2012 11:40:12 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>,
	Minchan Kim <minchan@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
	Jiri Kosina <jiri.kosina@...e.com>, Mel Gorman <mel@....ul.ie>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-mm <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v1 1/3] mm: teach mm by current context info to not do
 I/O during memory allocation

On Wed, Oct 17, 2012 at 4:19 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> The patch seems reasonable to me.  I'd like to see some examples of
> these resume-time callsite which are performing the GFP_KERNEL
> allocations, please.  You have found some kernel bugs, so those should
> be fully described.

OK, there are two examples of GFP_KERNEL allocation in subsystem
runtime resume path:

1), almost all devices in some pci platform
acpi_os_allocate
	<-acpi_ut_allocate
		<-ACPI_ALLOCATE_ZEROED
			<-acpi_evaluate_object
				<-__acpi_bus_set_power
					<-acpi_bus_set_power
						<-acpi_pci_set_power_state
							<-platform_pci_set_power_state
								<-pci_platform_power_transition
									<-__pci_complete_power_transition
										<-pci_set_power_state
											<-pci_restore_standard_config
												<-pci_pm_runtime_resume

2), all devices in usb subsystem
usb_get_status
	<-finish_port_resume
		<-usb_port_resume
			<-generic_resume
				<-usb_resume_device
					<-usb_resume_both
						<-usb_runtime_resume	

I also have many examples in which GFP_KERNEL allocation
is involved in runtime resume path of individual drivers.

The above two examples just show how difficult to solve the problem
by traditional way, :-)

Also as pointed by Oliver, network driver need memory allocation with
no io in iSCSI runtime resume situation too.

Thanks,
--
Ming Lei
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