From: Oliver Neukum <oneukum@suse.com>
To: Johan Hovold <johan@kernel.org>, Alan Stern <stern@rowland.harvard.edu>
Cc: Greg KH <greg@kroah.com>,
syzbot <syzbot+ada0f7d3d9fd2016d927@syzkaller.appspotmail.com>,
syzkaller-bugs@googlegroups.com,
USB mailing list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] USB: core: Make usb_start_wait_urb() interruptible
Date: Tue, 31 Aug 2021 12:47:52 +0200 [thread overview]
Message-ID: <54c4f3f9-412b-c093-6098-cbcc5828b320@suse.com> (raw)
In-Reply-To: <YS3y14DBrg0+n/iI@hovoldconsulting.com>
On 31.08.21 11:13, Johan Hovold wrote:
> The comment above usb_start_wait_urb() (which also needs to be updated,
> by the way) even suggests that drivers should "implement their own
> interruptible routines" so perhaps this has just gone unnoticed for 20
> odd years. And the question then becomes, why didn't we use
> interruptible sleep from the start?
>
> And trying to answer that I find that that's precisely what we did, but
> for some reason it was changed to uninterruptible sleep in v2.4.11
> without a motivation (that I could easily find spelled out).
I must admit that I do not remember. But there are a lot of situations
requiring control messages that do not allow signal delivery.
Take for example a device that is HID and storage. We are doing
HID error handling, which can involve a device reset. You absolutely
cannot deliver a signal right now, as you have a device that is in an
undefined
state in the block layer.
It looks to me very much like we need both versions and as a rule of thumb,
while you would use GFP_NOIO you must also use the uninterruptible
messaging.
Regards
Oliver
next prev parent reply other threads:[~2021-08-31 10:47 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-28 15:52 [syzbot] INFO: task hung in do_proc_bulk syzbot
2021-08-28 18:03 ` Alan Stern
2021-08-28 20:05 ` syzbot
2021-08-29 1:58 ` [PATCH] USB: core: Make usb_start_wait_urb() interruptible Alan Stern
2021-08-30 7:56 ` Johan Hovold
2021-08-30 14:46 ` Alan Stern
2021-08-30 15:11 ` Oliver Neukum
2021-08-30 16:09 ` Alan Stern
2021-08-31 8:52 ` Oliver Neukum
2021-08-31 9:13 ` Johan Hovold
2021-08-31 10:47 ` Oliver Neukum [this message]
2021-08-31 11:02 ` Oliver Neukum
2021-08-31 11:10 ` Johan Hovold
2021-08-31 17:03 ` Alan Stern
2021-09-01 8:16 ` Oliver Neukum
2021-09-02 20:04 ` [syzbot] INFO: task hung in do_proc_bulk Alan Stern
2021-09-02 20:46 ` syzbot
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