linux-usb.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: EJ Hsu <ejh@nvidia.com>
To: Oliver Neukum <oneukum@suse.com>, Alan Stern <stern@rowland.harvard.edu>
Cc: "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: [PATCH] usb: uas: fix a plug & unplug racing
Date: Tue, 21 Jan 2020 11:29:12 +0000	[thread overview]
Message-ID: <MN2PR12MB4126317E9BA1D269BE83E4EDCF0D0@MN2PR12MB4126.namprd12.prod.outlook.com> (raw)
In-Reply-To: <1579513114.17973.13.camel@suse.com>

Oliver Neukum wrote:

> > I just checked the code, and the reference count will be incremented
> > in scsi_scan_host(), precisely speaking, in scsi_autopm_get_host().
> > So, I still think we need to manually add reference count of interface here.
> > Please correct me if there is anything wrong.
> 
> AFAICT the generic power model will not suspend a parent while a child is
> active. The includes SCSI children of USB parents. So I think we are safe. Could
> you resubmit your patch without the PM counter manipulation and we can fix
> any issue that may exist in theory later?
> 

The child_count of usb device should be incremented in the scsi_scan_host().
I can simulate this situation by forcibly enable the autosuspend of uas driver
and add a delay before scsi_scan_host() is called in asynchronous way.

But for now, as uas driver does not support autosuspend, it is indeed safe to
remove the PM counter manipulation. If you have concern about it, it's OK 
to me to re-submit it.

Thanks,
EJ
--nvpublic


  reply	other threads:[~2020-01-21 11:29 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13  3:30 [PATCH] usb: uas: fix a plug & unplug racing EJ Hsu
2020-01-13  9:44 ` Oliver Neukum
2020-01-13 15:21   ` Alan Stern
2020-01-14  3:28   ` EJ Hsu
2020-01-14 14:41     ` Oliver Neukum
2020-01-14 15:04       ` Alan Stern
2020-01-15  9:31         ` Oliver Neukum
2020-01-15 15:17           ` Alan Stern
2020-01-15 15:54           ` EJ Hsu
2020-01-20  9:38             ` Oliver Neukum
2020-01-21 11:29               ` EJ Hsu [this message]
2020-01-22  9:52                 ` EJ Hsu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=MN2PR12MB4126317E9BA1D269BE83E4EDCF0D0@MN2PR12MB4126.namprd12.prod.outlook.com \
    --to=ejh@nvidia.com \
    --cc=linux-usb@vger.kernel.org \
    --cc=oneukum@suse.com \
    --cc=stern@rowland.harvard.edu \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).