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From: Oliver Neukum <oneukum@suse.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Andrey Konovalov <andreyknvl@google.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Colin Ian King <colin.king@canonical.com>,
	Arnd Bergmann <arnd@arndb.de>,
	USB list <linux-usb@vger.kernel.org>,
	syzbot <syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [PATCH] USB: cdc-wdm: Call wake_up_all() when clearing WDM_IN_USE bit.
Date: Thu, 02 Jul 2020 09:24:26 +0200	[thread overview]
Message-ID: <1593674666.3609.3.camel@suse.com> (raw)
In-Reply-To: <b347b882-a986-24c6-2b37-0b1a092931b9@i-love.sakura.ne.jp>

Am Donnerstag, den 02.07.2020, 14:44 +0900 schrieb Tetsuo Handa:

>  
>  	usb_autopm_put_interface(desc->intf)
>  	mutex_unlock(&desc->wlock);
> +	if (rv >= 0 &&
> +	    /*
> +	     * needs both flags. We cannot do with one
> +	     * because resetting it would cause a race
> +	     * with write() yet we need to signal
> +	     * a disconnect
> +	     */
> +	    wait_event_killable_timeout(desc->wait,
> +					!test_bit(WDM_IN_USE, &desc->flags) ||
> +					test_bit(WDM_DISCONNECTING, &desc->flags), 30 * HZ) == 0) {
> +		if (mutex_lock_killable(&desc->wlock) == 0) {
> +			if (!test_bit(WDM_DISCONNECTING, &desc->flags))
> +				dev_err(&desc->intf->dev,
> +					"Tx URB not responding index=%d\n",
> +					le16_to_cpu(req->wIndex));
> +			mutex_unlock(&desc->wlock);
> +		}
> +	}

Hi,

I am afraid this would

1. serialize the driver, harming performance
2. introduce a race with every timer a task is running

	Regards
		Oliver


  reply	other threads:[~2020-07-02  7:24 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
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 [this message]
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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