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Date:      Sat, 05 Jun 2021 22:30:37 +0000
From:      bugzilla-noreply@freebsd.org
To:        usb@FreeBSD.org
Subject:   [Bug 256296] "No Device" error after using asynchronous API of libusb once
Message-ID:  <bug-256296-19105-l2smbRnESO@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-256296-19105@https.bugs.freebsd.org/bugzilla/>
References:  <bug-256296-19105@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D256296

Sergii <sergii.dmytruk@3mdeb.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #225431|0                           |1
        is obsolete|                            |

--- Comment #6 from Sergii <sergii.dmytruk@3mdeb.com> ---
Created attachment 225579
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D225579&action=
=3Dedit
Better bug reproducer

Made a better example that showcases the bug. No help from debugger is
necessary. Demonstrates the issue 100% runs for me. Device is opened and cl=
osed
twice. Second time its opened there is a transfer attempt which always fails
(returns "no device" error).

The API is used properly as far as I can tell and the code "works" if you
remove sleep() calls, but doesn't if you leave them. I'm pretty confident t=
his
is a bug in libusb.

Another suggestion for a fix: before handling an event check whether device=
 is
still in the polling queue and if not, ignore the event. This might be the =
best
fix because the issue is that device is being polled after it was closed
(background thread was blocked on poll() at that time), so any events from =
this
device should be rightfully discarded as if it wasn't on the polling queue =
when
the event has arrived.

--=20
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