From: Stephen Boyd <sboyd@codeaurora.org>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Saravana Kannan <skannan@codeaurora.org>,
Kay Sievers <kay.sievers@vrfy.org>,
Greg KH <gregkh@linuxfoundation.org>,
Christian Lamparter <chunkeey@googlemail.com>,
linux-kernel@vger.kernel.org,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
alan@lxorguk.ukuu.org.uk,
Linux PM mailing list <linux-pm@vger.kernel.org>
Subject: Re: [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available
Date: Sun, 18 Mar 2012 23:32:08 -0700 [thread overview]
Message-ID: <4F66D2E8.2090906@codeaurora.org> (raw)
In-Reply-To: <201203181301.19048.rjw@sisk.pl>
On 3/18/2012 5:01 AM, Rafael J. Wysocki wrote:
> On Sunday, March 18, 2012, Stephen Boyd wrote:
>
>> Ok. I like where nowait() is going in the other part of the thread but
>> I'm still confused about when request_firmware() is correct to use. It
>> seems that the function is inherently racy with freezing. Does every
>> user of request_firmware() need to synchronize with freezing?
>>
>> For example, if one CPU is in the middle of a driver probe that makes a
>> request_firmware() call and another CPU is starting to suspend we will
>> have a race between usermodehelpers being disabled and the
>> request_firmware() call acquiring the usermodehelper rwsem. If the
>> suspending CPU wins the race it will disable usermodehelpers and the
>> request_firmware() call will return -EBUSY and warn.
> Yes, it will.
That sounds wrong then, no? Why don't we have request_firmware() do a
read_lock on the usermodehelpers sem and then have suspend do a write
lock, disable usermodehelpers, wait for any users to finish, freeze
processes and then unlock the write lock? That way we don't hit a case
where request_firmware() races with suspend, and we don't have to change
the warning or conditional.
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
next prev parent reply other threads:[~2012-03-19 6:32 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-03 20:22 [RFC] firmware loader: retry _nowait requests when userhelper is not yet available Christian Lamparter
2012-03-03 23:57 ` Alan Cox
2012-03-04 1:50 ` Christian Lamparter
2012-03-05 20:12 ` Srivatsa S. Bhat
2012-03-09 22:30 ` [PATCH] firmware loader: don't cancel _nowait requests when helper " Christian Lamparter
2012-03-09 23:36 ` Greg KH
2012-03-10 0:52 ` Christian Lamparter
2012-03-11 11:56 ` Kay Sievers
2012-03-13 9:37 ` Saravana Kannan
2012-03-13 9:43 ` Saravana Kannan
2012-03-13 20:14 ` Rafael J. Wysocki
2012-03-14 19:21 ` Stephen Boyd
2012-03-14 23:04 ` Rafael J. Wysocki
2012-03-14 23:13 ` Rafael J. Wysocki
2012-03-14 23:17 ` Stephen Boyd
2012-03-14 23:34 ` Rafael J. Wysocki
2012-03-14 23:38 ` Stephen Boyd
2012-03-15 0:11 ` Rafael J. Wysocki
2012-03-15 19:50 ` [PATCH] firmware_class: Move request_firmware_nowait() to workqueues Stephen Boyd
2012-03-15 20:07 ` Christian Lamparter
2012-03-15 20:12 ` Stephen Boyd
2012-03-15 22:31 ` Rafael J. Wysocki
2012-03-16 1:39 ` Stephen Boyd
2012-03-16 20:19 ` Rafael J. Wysocki
2012-03-16 20:26 ` Stephen Boyd
2012-03-16 21:45 ` Rafael J. Wysocki
2012-03-16 22:18 ` Christian Lamparter
2012-03-16 22:35 ` Rafael J. Wysocki
2012-03-17 2:47 ` [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available Stephen Boyd
2012-03-17 5:51 ` Linus Torvalds
2012-03-17 20:06 ` Rafael J. Wysocki
2012-03-18 8:26 ` Stephen Boyd
2012-03-18 12:01 ` Rafael J. Wysocki
2012-03-19 6:32 ` Stephen Boyd [this message]
2012-03-19 11:24 ` Rafael J. Wysocki
2012-03-19 23:00 ` Rafael J. Wysocki
2012-03-25 22:00 ` [PATCH 0/6] firmware_class: Fix problems with usermodehelper test Rafael J. Wysocki
2012-03-25 22:01 ` [PATCH 1/6] firmware_class: Rework usermodehelper check Rafael J. Wysocki
2012-03-25 22:01 ` [PATCH 2/6] firmware_class: Split _request_firmware() into three functions Rafael J. Wysocki
2012-03-26 18:15 ` Stephen Boyd
2012-03-26 18:21 ` Stephen Boyd
2012-03-26 20:12 ` Rafael J. Wysocki
2012-03-26 20:31 ` Stephen Boyd
2012-03-26 20:36 ` Rafael J. Wysocki
2012-03-27 21:35 ` Stephen Boyd
2012-03-27 21:51 ` Rafael J. Wysocki
2012-03-25 22:02 ` [PATCH 3/6] firmware_class: Do not warn that system is not ready from async loads Rafael J. Wysocki
2012-03-25 22:03 ` [PATCH 4/6] PM / Hibernate: Disable usermode helpers right before freezing tasks Rafael J. Wysocki
2012-03-25 22:03 ` [PATCH 5/6] PM / Sleep: Move disabling of usermode helpers to the freezer Rafael J. Wysocki
2012-03-25 22:04 ` [PATCH 6/6] PM / Sleep: Mitigate race between the freezer and request_firmware() Rafael J. Wysocki
2012-03-26 18:16 ` Stephen Boyd
2012-03-26 20:06 ` Rafael J. Wysocki
2012-03-27 21:25 ` Stephen Boyd
2012-03-27 21:37 ` Rafael J. Wysocki
2012-03-26 18:42 ` [PATCH 0/6] firmware_class: Fix problems with usermodehelper test Greg KH
2012-03-26 20:37 ` Rafael J. Wysocki
2012-03-27 21:28 ` [PATCH 1/2] firmware_class: Reorganize fw_create_instance() Stephen Boyd
2012-03-27 21:47 ` Rafael J. Wysocki
2012-03-27 21:49 ` Greg KH
2012-03-27 21:56 ` Rafael J. Wysocki
2012-03-27 21:28 ` [PATCH 2/2] firmware_class: Move request_firmware_nowait() to workqueues Stephen Boyd
2012-03-27 21:49 ` Rafael J. Wysocki
2012-03-27 22:01 ` Tejun Heo
2012-03-27 22:21 ` Rafael J. Wysocki
2012-03-27 22:48 ` Tejun Heo
2012-03-27 22:55 ` Rafael J. Wysocki
2012-03-27 23:02 ` Stephen Boyd
2012-03-27 23:05 ` Stephen Boyd
2012-03-28 21:19 ` [PATCH v2 0/8] firmware_class: Fix problems with usermodehelper test Rafael J. Wysocki
2012-03-28 21:20 ` [PATCH v2 1/8] firmware_class: Rework usermodehelper check Rafael J. Wysocki
2012-03-28 21:21 ` [PATCH v2 2/8] firmware_class: Split _request_firmware() into three functions, v2 Rafael J. Wysocki
2012-03-28 21:22 ` [PATCH v3 3/8] firmware_class: Do not warn that system is not ready from async loads Rafael J. Wysocki
2012-03-28 21:23 ` [PATCH v2 4/8] PM / Hibernate: Disable usermode helpers right before freezing tasks Rafael J. Wysocki
2012-03-28 21:23 ` [PATCH v2 5/8] PM / Sleep: Move disabling of usermode helpers to the freezer Rafael J. Wysocki
2012-03-28 21:24 ` [PATCH v2 6/8] PM / Sleep: Mitigate race between the freezer and request_firmware() Rafael J. Wysocki
2012-03-28 21:25 ` [PATCH v2 7/8] firmware_class: Reorganize fw_create_instance() Rafael J. Wysocki
2012-03-28 21:26 ` [PATCH v2 8/8] firmware_class: Move request_firmware_nowait() to workqueues Rafael J. Wysocki
2012-03-14 23:19 ` [PATCH] firmware loader: don't cancel _nowait requests when helper is not yet available Rafael J. Wysocki
2012-03-13 19:42 ` Rafael J. Wysocki
2012-03-13 23:25 ` Kay Sievers
2012-03-14 0:10 ` Rafael J. Wysocki
2012-03-14 0:14 ` Kay Sievers
2012-03-14 0:54 ` Linus Torvalds
2012-03-14 1:43 ` Kay Sievers
2012-03-14 1:51 ` Linus Torvalds
2012-03-14 1:55 ` Kay Sievers
2012-03-14 2:00 ` Kay Sievers
2012-03-14 2:21 ` Linus Torvalds
2012-03-14 15:07 ` Srivatsa S. Bhat
2012-03-14 22:54 ` Rafael J. Wysocki
2012-03-16 7:14 ` Srivatsa S. Bhat
2012-03-16 20:23 ` Rafael J. Wysocki
2012-03-16 21:14 ` Christian Lamparter
2012-03-16 21:19 ` Linus Torvalds
2012-03-19 7:06 ` Srivatsa S. Bhat
2012-03-16 22:19 ` [RFC] firmware loader: retry _nowait requests when userhelper " Rafael J. Wysocki
2012-03-16 22:25 ` Christian Lamparter
2012-03-16 22:57 ` Rafael J. Wysocki
2012-03-16 23:35 ` Christian Lamparter
2012-03-16 23:37 ` Linus Torvalds
2012-03-17 0:23 ` Rafael J. Wysocki
2012-03-17 0:33 ` Linus Torvalds
2012-03-18 0:29 ` Rafael J. Wysocki
2012-03-18 2:21 ` Linus Torvalds
2012-03-18 12:21 ` Rafael J. Wysocki
2012-03-18 12:43 ` Christian Lamparter
2012-03-18 23:15 ` [PATCH 0/3] firmware_class: Fix problem with async requests (was: Re: [RFC] firmware loader: retry ...) Rafael J. Wysocki
2012-03-18 23:17 ` [PATCH 1/3] firmware_class: Rework usermodehelper check Rafael J. Wysocki
2012-03-18 23:18 ` [PATCH 2/3] firmware_class: Split _request_firmware() into three functions Rafael J. Wysocki
2012-03-18 23:21 ` [PATCH 3/3] firmware_class: Do not warn that system is not ready for async loads Rafael J. Wysocki
2012-03-19 12:41 ` [RFC] firmware loader: retry _nowait requests when userhelper is not yet available James Courtier-Dutton
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