From patchwork Sun Jul 10 02:23:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12912385 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14122C43334 for ; Sun, 10 Jul 2022 02:24:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229454AbiGJCYC (ORCPT ); Sat, 9 Jul 2022 22:24:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229450AbiGJCYA (ORCPT ); Sat, 9 Jul 2022 22:24:00 -0400 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D05BAA1B7 for ; Sat, 9 Jul 2022 19:23:59 -0700 (PDT) Received: from fsav314.sakura.ne.jp (fsav314.sakura.ne.jp [153.120.85.145]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 26A2NboS087954; Sun, 10 Jul 2022 11:23:38 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav314.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav314.sakura.ne.jp); Sun, 10 Jul 2022 11:23:37 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav314.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 26A2Nb0f087949 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 10 Jul 2022 11:23:37 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <03096156-3478-db03-c015-28643479116c@I-love.SAKURA.ne.jp> Date: Sun, 10 Jul 2022 11:23:33 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Content-Language: en-US To: Greg KH , Oliver Neukum , Wedson Almeida Filho , "Rafael J. Wysocki" , Arjan van de Ven , Len Brown , Dmitry Vyukov Cc: linux-pm@vger.kernel.org, LKML From: Tetsuo Handa Subject: [PATCH v2 1/4] char: misc: allow calling open() callback without misc_mtx held Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org syzbot is reporting hung task at misc_open() [1], for there is a race window of AB-BA deadlock which involves probe_count variable. Currently, wait_for_device_probe() from snapshot_open() from misc_open() can sleep forever with misc_mtx held if probe_count cannot become 0. When a device is probed, probe_count is incremented before the probe function starts, and probe_count is decremented after the probe function completed. When USB storage device "sddr09" is probed by hub_event() work in usb_hub_wq workqueue, sddr09_probe() is called with elevated probe_count. Inside sddr09_probe(), usb_stor_msg_common() from usb_stor_ctrl_transfer() calls wait_for_completion_interruptible_timeout() (w_f_c_i_t() afterward) with no timeout. If sddr09 device does not respond (when using real hardware, or cannot respond when using emulated hardware), w_f_c_i_t() cannot return, which means that probe_count cannot be decremented. According to Oliver Neukum, we can't pass some timeout when calling usb_stor_msg_common() from usb_stor_ctrl_transfer(), for the timeout is supposed to come from the SCSI layer in the general case. The reason why syzkaller processes cannot make w_f_c_i_t() return is that, w_f_c_i_t() can return when a syzkaller process which is emulating a USB device calls fput() on /dev/raw-gadget due to process termination. When we run the reproducer, the syzkaller process which is emulating a USB device cannot call fput() on /dev/raw-gadget because that process is blocked at mutex_lock(&misc_mtx) in misc_open(). The process which is holding misc_mtx is waiting for probe_count to become 0, but the probe function which is called from hub_event() is waiting for the processes which are blocked at mutex_lock(&misc_mtx) to call close() on /dev/raw-gadget. This is the phenomenon syzbot is reporting. Therefore, as one of steps for making it possible to recover from such situation, this patch allows miscdev to call its open() callback without misc_mtx held. Wedson Almeida Filho worried that this change breaks the invariants of miscdev that driver's open() callback will not be made after once misc_deregister() is called. But since /dev/snapshot driver does not call misc_deregister(), I consider that this change is safe for allowing snapshot_open() to be called from misc_open() without misc_mtx held. Note that lock_system_sleep() from snapshot_open() has the same problem with mutex_lock(&misc_mtx) from misc_open(). This patch alone makes more hard to debug, for khungtaskd no longer complains about lock_system_sleep() because lock_system_sleep() sets PF_FREEZER_SKIP flag before calling mutex_lock(&system_transition_mutex). How to avoid unbounded uninterruptible sleeping on system_transition_mutex with PF_FREEZER_SKIP flag set deserves different patches. Link: https://syzkaller.appspot.com/bug?extid=358c9ab4c93da7b7238c [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa Cc: Greg KH Cc: Oliver Neukum Cc: Wedson Almeida Filho Cc: Rafael J. Wysocki Cc: Arjan van de Ven --- Changes in v2: Call open() without misc_mtx, instread of making misc_mtx killable. Split into 3 (+ 1 optional) patches. v1 is at at https://lkml.kernel.org/r/72e74af9-f1b6-e383-a2c3-6ee8a0aea5e0@I-love.SAKURA.ne.jp . drivers/char/misc.c | 4 ++++ include/linux/miscdevice.h | 1 + kernel/power/user.c | 1 + 3 files changed, 6 insertions(+) diff --git a/drivers/char/misc.c b/drivers/char/misc.c index cba19bfdc44d..709a902e401b 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -139,6 +139,10 @@ static int misc_open(struct inode *inode, struct file *file) err = 0; replace_fops(file, new_fops); + if (c->unlocked_open && file->f_op->open) { + mutex_unlock(&misc_mtx); + return file->f_op->open(inode, file); + } if (file->f_op->open) err = file->f_op->open(inode, file); fail: diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h index 0676f18093f9..e112ef9e3b7b 100644 --- a/include/linux/miscdevice.h +++ b/include/linux/miscdevice.h @@ -86,6 +86,7 @@ struct miscdevice { const struct attribute_group **groups; const char *nodename; umode_t mode; + bool unlocked_open; }; extern int misc_register(struct miscdevice *misc); diff --git a/kernel/power/user.c b/kernel/power/user.c index ad241b4ff64c..59912060109f 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -441,6 +441,7 @@ static struct miscdevice snapshot_device = { .minor = SNAPSHOT_MINOR, .name = "snapshot", .fops = &snapshot_fops, + .unlocked_open = true, /* Call snapshot_open() with no locks held. */ }; static int __init snapshot_device_init(void) From patchwork Sun Jul 10 02:24:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12912387 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 532C7C433EF for ; Sun, 10 Jul 2022 02:25:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229571AbiGJCZp (ORCPT ); Sat, 9 Jul 2022 22:25:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34280 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229566AbiGJCZo (ORCPT ); Sat, 9 Jul 2022 22:25:44 -0400 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A0BAA1BC for ; Sat, 9 Jul 2022 19:25:43 -0700 (PDT) Received: from fsav114.sakura.ne.jp (fsav114.sakura.ne.jp [27.133.134.241]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 26A2OADU088041; Sun, 10 Jul 2022 11:24:10 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav114.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav114.sakura.ne.jp); Sun, 10 Jul 2022 11:24:10 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav114.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 26A2O9sl088038 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 10 Jul 2022 11:24:10 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <48d01ce7-e028-c103-ea7f-5a4ea4c8930b@I-love.SAKURA.ne.jp> Date: Sun, 10 Jul 2022 11:24:06 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: [PATCH v2 2/4] PM: hibernate: call wait_for_device_probe() without system_transition_mutex held Content-Language: en-US From: Tetsuo Handa To: Greg KH , Oliver Neukum , Wedson Almeida Filho , "Rafael J. Wysocki" , Arjan van de Ven , Len Brown , Dmitry Vyukov Cc: linux-pm@vger.kernel.org, LKML References: <03096156-3478-db03-c015-28643479116c@I-love.SAKURA.ne.jp> In-Reply-To: <03096156-3478-db03-c015-28643479116c@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org syzbot is reporting hung task at misc_open() [1], for there is a race window of AB-BA deadlock which involves probe_count variable. Even with "char: misc: allow calling open() callback without misc_mtx held", wait_for_device_probe() (w_f_d_p() afterward) from snapshot_open() can sleep forever if probe_count cannot become 0. w_f_d_p() in snapshot_open() was added by commit c751085943362143 ("PM/Hibernate: Wait for SCSI devices scan to complete during resume"), "In addition, if the resume from hibernation is userland-driven, it's better to wait for all device probes in the kernel to complete before attempting to open the resume device." but that commit did not take into account possibility of unresponsive hardware, for the timeout is supposed to come from the SCSI layer in the general case. syzbot is reporting that USB storage, which is a very tiny wrapper around the whole SCSI protocol, is failing to apply timeout. Fortunately, holding system_transition_mutex is not required when waiting for device probe. Therefore, as one of steps for making it possible to recover from such situation, this patch changes snapshot_open() to call w_f_d_p() before calling lock_system_sleep(). Note that the problem that w_f_d_p() can sleep too long to wait remains. But how to fix that part deserves different patches. Link: https://syzkaller.appspot.com/bug?extid=358c9ab4c93da7b7238c [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa Cc: Greg KH Cc: Oliver Neukum Cc: Wedson Almeida Filho Cc: Rafael J. Wysocki Cc: Arjan van de Ven --- kernel/power/user.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/kernel/power/user.c b/kernel/power/user.c index 59912060109f..db98a028dfdd 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -51,6 +51,18 @@ static int snapshot_open(struct inode *inode, struct file *filp) if (!hibernation_available()) return -EPERM; + switch (filp->f_flags & O_ACCMODE) { + case O_RDWR: /* Can't do both at the same time. */ + return -ENOSYS; + case O_RDONLY: /* Hibernating */ + /* The image device should be already ready. */ + break; + default: /* Resuming */ + /* We may need to wait for the image device to appear. */ + wait_for_device_probe(); + break; + } + lock_system_sleep(); if (!hibernate_acquire()) { @@ -58,28 +70,16 @@ static int snapshot_open(struct inode *inode, struct file *filp) goto Unlock; } - if ((filp->f_flags & O_ACCMODE) == O_RDWR) { - hibernate_release(); - error = -ENOSYS; - goto Unlock; - } nonseekable_open(inode, filp); data = &snapshot_state; filp->private_data = data; memset(&data->handle, 0, sizeof(struct snapshot_handle)); if ((filp->f_flags & O_ACCMODE) == O_RDONLY) { - /* Hibernating. The image device should be accessible. */ data->swap = swap_type_of(swsusp_resume_device, 0); data->mode = O_RDONLY; data->free_bitmaps = false; error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION); } else { - /* - * Resuming. We may need to wait for the image device to - * appear. - */ - wait_for_device_probe(); - data->swap = -1; data->mode = O_WRONLY; error = pm_notifier_call_chain_robust(PM_RESTORE_PREPARE, PM_POST_RESTORE); From patchwork Sun Jul 10 02:25:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12912386 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A063C433EF for ; Sun, 10 Jul 2022 02:25:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229450AbiGJCZc (ORCPT ); Sat, 9 Jul 2022 22:25:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229571AbiGJCZb (ORCPT ); Sat, 9 Jul 2022 22:25:31 -0400 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 24FB0B859 for ; Sat, 9 Jul 2022 19:25:31 -0700 (PDT) Received: from fsav119.sakura.ne.jp (fsav119.sakura.ne.jp [27.133.134.246]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 26A2PB5m088316; Sun, 10 Jul 2022 11:25:11 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav119.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav119.sakura.ne.jp); Sun, 10 Jul 2022 11:25:11 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav119.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 26A2PBf0088313 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 10 Jul 2022 11:25:11 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <2646e8a3-cc9f-c2c5-e4d6-c86de6e1b739@I-love.SAKURA.ne.jp> Date: Sun, 10 Jul 2022 11:25:08 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: [PATCH v2 3/4] PM: hibernate: allow wait_for_device_probe() to timeout when resuming from hibernation Content-Language: en-US From: Tetsuo Handa To: Greg KH , Oliver Neukum , Wedson Almeida Filho , "Rafael J. Wysocki" , Arjan van de Ven , Len Brown , Dmitry Vyukov Cc: linux-pm@vger.kernel.org, LKML References: <03096156-3478-db03-c015-28643479116c@I-love.SAKURA.ne.jp> <48d01ce7-e028-c103-ea7f-5a4ea4c8930b@I-love.SAKURA.ne.jp> In-Reply-To: <48d01ce7-e028-c103-ea7f-5a4ea4c8930b@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org syzbot is reporting hung task at misc_open() [1], for there is a race window of AB-BA deadlock which involves probe_count variable. Even with "char: misc: allow calling open() callback without misc_mtx held" and "PM: hibernate: call wait_for_device_probe() without system_transition_mutex held", wait_for_device_probe() from snapshot_open() can sleep forever if probe_count cannot become 0. Since snapshot_open() is a userland-driven hibernation/resume request, it should be acceptable to fail if something is wrong. Users would not want to wait for hours if device stopped responding. Therefore, introduce killable version of wait_for_device_probe() with timeout. According to Oliver Neukum, there are SCSI commands that can run for more than 60 seconds. Therefore, this patch choose 5 minutes for timeout. Link: https://syzkaller.appspot.com/bug?extid=358c9ab4c93da7b7238c [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa Cc: Greg KH Cc: Oliver Neukum Cc: Wedson Almeida Filho Cc: Rafael J. Wysocki Cc: Arjan van de Ven --- drivers/base/dd.c | 14 ++++++++++++++ include/linux/device/driver.h | 1 + kernel/power/user.c | 9 +++++++-- 3 files changed, 22 insertions(+), 2 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 70f79fc71539..3136b8403bb0 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -724,6 +724,20 @@ void wait_for_device_probe(void) } EXPORT_SYMBOL_GPL(wait_for_device_probe); +void wait_for_device_probe_killable_timeout(unsigned long timeout) +{ + /* wait for probe timeout */ + wait_event(probe_timeout_waitqueue, !driver_deferred_probe_timeout); + + /* wait for the deferred probe workqueue to finish */ + flush_work(&deferred_probe_work); + + /* wait for the known devices to complete their probing */ + wait_event_killable_timeout(probe_waitqueue, + atomic_read(&probe_count) == 0, timeout); + async_synchronize_full(); +} + static int __driver_probe_device(struct device_driver *drv, struct device *dev) { int ret = 0; diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h index 7acaabde5396..4ee909144470 100644 --- a/include/linux/device/driver.h +++ b/include/linux/device/driver.h @@ -129,6 +129,7 @@ extern struct device_driver *driver_find(const char *name, struct bus_type *bus); extern int driver_probe_done(void); extern void wait_for_device_probe(void); +extern void wait_for_device_probe_killable_timeout(unsigned long timeout); void __init wait_for_init_devices_probe(void); /* sysfs interface for exporting driver attributes */ diff --git a/kernel/power/user.c b/kernel/power/user.c index db98a028dfdd..32dd5a855e8c 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -58,8 +58,13 @@ static int snapshot_open(struct inode *inode, struct file *filp) /* The image device should be already ready. */ break; default: /* Resuming */ - /* We may need to wait for the image device to appear. */ - wait_for_device_probe(); + /* + * Since the image device might not be ready, try to wait up to + * 5 minutes. We should not wait forever, for we might get stuck + * due to unresponsive devices and/or new probe events which + * are irrelevant to the image device keep coming in. + */ + wait_for_device_probe_killable_timeout(300 * HZ); break; } From patchwork Sun Jul 10 02:25:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tetsuo Handa X-Patchwork-Id: 12912388 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3785BC43334 for ; Sun, 10 Jul 2022 02:26:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229562AbiGJC0L (ORCPT ); Sat, 9 Jul 2022 22:26:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbiGJC0L (ORCPT ); Sat, 9 Jul 2022 22:26:11 -0400 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2AFA9B859 for ; Sat, 9 Jul 2022 19:26:10 -0700 (PDT) Received: from fsav118.sakura.ne.jp (fsav118.sakura.ne.jp [27.133.134.245]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 26A2Pp8d088449; Sun, 10 Jul 2022 11:25:51 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav118.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav118.sakura.ne.jp); Sun, 10 Jul 2022 11:25:51 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav118.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 26A2PpbT088446 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 10 Jul 2022 11:25:51 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <273ec8c8-8b70-0a0e-4688-5b943ac8e648@I-love.SAKURA.ne.jp> Date: Sun, 10 Jul 2022 11:25:47 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: [PATCH v2 4/4] PM: hibernate: don't set PF_FREEZER_SKIP flag when manipulating /dev/snapshot Content-Language: en-US From: Tetsuo Handa To: Greg KH , Oliver Neukum , Wedson Almeida Filho , "Rafael J. Wysocki" , Arjan van de Ven , Len Brown , Dmitry Vyukov Cc: linux-pm@vger.kernel.org, LKML References: <03096156-3478-db03-c015-28643479116c@I-love.SAKURA.ne.jp> <48d01ce7-e028-c103-ea7f-5a4ea4c8930b@I-love.SAKURA.ne.jp> <2646e8a3-cc9f-c2c5-e4d6-c86de6e1b739@I-love.SAKURA.ne.jp> In-Reply-To: <2646e8a3-cc9f-c2c5-e4d6-c86de6e1b739@I-love.SAKURA.ne.jp> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Since khungtaskd skips threads with PF_FREEZER_SKIP flag set, currently we can't report unbounded uninterruptible sleep when something went wrong while manipulating /dev/snapshot interface. Let's change snapshot_{open,read,write}() to use mutex_lock_killable() and change snapshot_release() to use mutex_lock(), so that khungtaskd can report unbounded uninterruptible sleep, by not setting PF_FREEZER_SKIP flag. Since /dev/snapshot is exclusive due to hibernate_acquire(), we could choose mutex_trylock() for snapshot_{open,read,write}() as with snapshot_ioctl(). But until we confirm that this patch does not break something, let's stay mutex_lock_killable(). Signed-off-by: Tetsuo Handa Cc: "Rafael J. Wysocki" Cc: Len Brown Cc: Pavel Machek --- This patch is only compile tested. Need to review if somewhere depends on PF_FREEZER_SKIP flag being set. kernel/power/user.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/kernel/power/user.c b/kernel/power/user.c index 32dd5a855e8c..9936efa07022 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -68,7 +68,8 @@ static int snapshot_open(struct inode *inode, struct file *filp) break; } - lock_system_sleep(); + if (mutex_lock_killable(&system_transition_mutex)) + return -EINTR; if (!hibernate_acquire()) { error = -EBUSY; @@ -102,7 +103,7 @@ static int snapshot_open(struct inode *inode, struct file *filp) data->dev = 0; Unlock: - unlock_system_sleep(); + mutex_unlock(&system_transition_mutex); return error; } @@ -111,7 +112,7 @@ static int snapshot_release(struct inode *inode, struct file *filp) { struct snapshot_data *data; - lock_system_sleep(); + mutex_lock(&system_transition_mutex); swsusp_free(); data = filp->private_data; @@ -128,7 +129,7 @@ static int snapshot_release(struct inode *inode, struct file *filp) PM_POST_HIBERNATION : PM_POST_RESTORE); hibernate_release(); - unlock_system_sleep(); + mutex_unlock(&system_transition_mutex); return 0; } @@ -140,7 +141,8 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf, ssize_t res; loff_t pg_offp = *offp & ~PAGE_MASK; - lock_system_sleep(); + if (mutex_lock_killable(&system_transition_mutex)) + return -EINTR; data = filp->private_data; if (!data->ready) { @@ -161,7 +163,7 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf, *offp += res; Unlock: - unlock_system_sleep(); + mutex_unlock(&system_transition_mutex); return res; } @@ -173,7 +175,8 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf, ssize_t res; loff_t pg_offp = *offp & ~PAGE_MASK; - lock_system_sleep(); + if (mutex_lock_killable(&system_transition_mutex)) + return -EINTR; data = filp->private_data; @@ -195,7 +198,7 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf, if (res > 0) *offp += res; unlock: - unlock_system_sleep(); + mutex_unlock(&system_transition_mutex); return res; }