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Date:   Tue, 26 Nov 2019 10:18:07 -0500 (EST)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Jiri Kosina <jikos@kernel.org>
cc:     syzbot <syzbot+ec5f884c4a135aa0dbb9@syzkaller.appspotmail.com>,
        <andreyknvl@google.com>, <benjamin.tissoires@redhat.com>,
        <linux-input@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-usb@vger.kernel.org>, <syzkaller-bugs@googlegroups.com>
Subject: Re: INFO: rcu detected stall in hub_event
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On Tue, 26 Nov 2019, Jiri Kosina wrote:

> On Mon, 25 Nov 2019, Alan Stern wrote:
> 
> > #syz test: https://github.com/google/kasan.git 46178223
> 
> Alan, did you get a test result from syzbot on this patch? My mailbox 
> doesn't seem to have it.

No response, not yet.  syzbot seems to be very slow testing the patches
for this bug report.  The earlier ones I submitted also took over a day
to finish.

BTW, even if this patch fixes the problem, I don't think setting 
collection[0].parent_idx to -1 is a very good solution.  It's brittle 
and doesn't address the underlying ambiguity.

Alan Stern