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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Greg KH <greg@kroah.com>
Cc: Colin Ian King <colin.king@canonical.com>,
	Oliver Neukum <oneukum@suse.com>, Arnd Bergmann <arnd@arndb.de>,
	linux-usb@vger.kernel.org
Subject: Re: [PATCH] USB: cdc-wdm: Call wake_up_all() when clearing WDM_IN_USE bit.
Date: Thu, 21 May 2020 19:01:13 +0900	[thread overview]
Message-ID: <177cc23a-60a7-f5cd-09d6-57608727ea27@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20200521073323.GA2579717@kroah.com>

On 2020/05/21 16:33, Greg KH wrote:
> On Thu, May 21, 2020 at 08:31:29AM +0900, Tetsuo Handa wrote:
>> Since e.g. wdm_flush() calls wait_event() on WDM_IN_USE bit,
>> make sure to call wake_up_all() when clearing WDM_IN_USE bit.
> 
> I'm sorry, but I don't understand what this changelog text is trying to
> say.  Can you reword this differently?

wait_event("condition") wants corresponding wake_up() (or its variant)
after making "condition" == true. For example, wdm_flush() calls

	wait_event(desc->wait,
			/*
			 * needs both flags. We cannot do with one
			 * because resetting it would cause a race
			 * with write() yet we need to signal
			 * a disconnect
			 */
			!test_bit(WDM_IN_USE, &desc->flags) ||
			test_bit(WDM_DISCONNECTING, &desc->flags));

but wdm_write() is not calling wake_up(&desc->wait) after
clear_bit(WDM_IN_USE, &desc->flags) when usb_submit_urb() failed.

> And is this a bugfix?  For what?  Does it need to go to stable kernels?

Potential bugfix. syzbot is reporting two bugs that hung at wdm_flush(),
but I think that this patch won't fix these bugs. Therefore, I don't think
this patch needs to go to stable kernels.


  reply	other threads:[~2020-05-21 10:01 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20 23:31 [PATCH] USB: cdc-wdm: Call wake_up_all() when clearing WDM_IN_USE bit Tetsuo Handa
2020-05-21  7:33 ` Greg KH
2020-05-21 10:01   ` Tetsuo Handa [this message]
2020-05-21 19:50     ` Oliver Neukum
2020-05-21 22:48       ` Tetsuo Handa
2020-05-22  8:04         ` Oliver Neukum
2020-05-22  8:26           ` Tetsuo Handa
2020-05-25 12:06             ` Oliver Neukum
2020-05-25 13:32               ` Tetsuo Handa
2020-05-27  4:47                 ` Tetsuo Handa
2020-05-28 15:18                   ` Andrey Konovalov
2020-05-28 16:03                     ` Tetsuo Handa
2020-05-28 19:03                       ` Andrey Konovalov
2020-05-28 19:40                         ` Alan Stern
2020-05-28 19:51                           ` Andrey Konovalov
2020-05-28 20:58                             ` Alan Stern
2020-05-29 20:41                               ` Andrey Konovalov
2020-05-30  0:42                                 ` Tetsuo Handa
2020-05-30  1:10                                   ` Alan Stern
2020-05-30  4:58                                     ` Tetsuo Handa
2020-06-24 11:57                                       ` Oliver Neukum
2020-06-24 12:48                                         ` Tetsuo Handa
2020-05-30  6:08                                   ` Greg Kroah-Hartman
2020-06-01 12:26                                   ` Andrey Konovalov
2020-05-30 15:25                               ` Oliver Neukum
2020-05-30 15:47                                 ` Alan Stern
2020-06-08  2:24                                   ` Tetsuo Handa
2020-06-18  0:48                                     ` Tetsuo Handa
2020-06-19 13:56                                       ` Andrey Konovalov
2020-06-23 11:20                                         ` Tetsuo Handa
2020-07-02  5:44                                           ` Tetsuo Handa
2020-07-02  7:24                                             ` Oliver Neukum
2020-07-15  6:15                                               ` Tetsuo Handa
2020-08-10 10:47                                                 ` Tetsuo Handa
2020-09-24 15:09                                                   ` [PATCH] USB: cdc-wdm: Make wdm_flush() interruptible and add wdm_fsync() Tetsuo Handa
2020-09-28 14:17                                                     ` [PATCH (repost)] " Tetsuo Handa
2020-06-25  9:56                                     ` [PATCH] USB: cdc-wdm: Call wake_up_all() when clearing WDM_IN_USE bit Oliver Neukum
2020-06-25 11:15                                       ` Tetsuo Handa
2020-07-01  7:08                                     ` [TEST]Re: " Oliver Neukum

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