Date: Sat, 9 Mar 2019 18:26:40 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Hans Petter Selasky <hps@selasky.org> Cc: "O'Connor, Daniel" <darius@dons.net.au>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: USB stack getting confused Message-ID: <20190309162640.GN2492@kib.kiev.ua> In-Reply-To: <ea6e2690-1ad7-6c06-49e5-c528013f26c0@selasky.org> References: <E0371188-FD0A-47E1-8378-40239F5C6622@dons.net.au> <f3e6e30b-8b62-546b-2b51-e841f2e645bd@selasky.org> <3B29D870-41F9-46AF-B9F3-03106DEC417D@dons.net.au> <20190309152613.GM2492@kib.kiev.ua> <ea6e2690-1ad7-6c06-49e5-c528013f26c0@selasky.org>
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On Sat, Mar 09, 2019 at 04:42:50PM +0100, Hans Petter Selasky wrote: > On 3/9/19 4:26 PM, Konstantin Belousov wrote: > > On Sat, Mar 09, 2019 at 08:59:30PM +1030, O'Connor, Daniel wrote: > >> > >> > >>> On 9 Mar 2019, at 19:30, Hans Petter Selasky <hps@selasky.org> wrote: > >>> On 3/9/19 12:08 AM, O'Connor, Daniel wrote: > >>>> My program normally runs continually doing acquisitions of data for N seconds, doing some checks and restarting. After a while (~30 1 minute acquisitions or ~8 30 minute ones) my program can't 'see' the device (it uses libusb10) any more (it reconnects each acquisition for $REASONS). Also pretty weirdly usbconfig can't see it either(!). > >>> > >>> What is printed in dmesg? Maybe the device has a problem. > >> > >> There is nothing in dmesg - no disconnect / reconnect etc. > >> > >> If I hold the user space process in gdb 'forever' (eg over night) usbconfig doesn't see the device, but the moment I quit the user space process it can be seen again. > > > > Does it mean that the file descriptor opened for ugen has a chance to > > be closed ? > > The USB stack will wait for all FDs to be closed during detach also via > destroy_dev(). So my guess was correct. Do you agree that this behaviour is wrong ? In fact I saw something similar with apcupsd and either usb/com adapters or native usb control card for APC UPSes. For reasons I do not understand, these devices are often disconnected. For older versions of apcupsd, it required restart for newly reattached device to be recreated in /dev. Sometimes it hangs whole usb stack. Newer apcupsd seems to open /dev/ugen only for the duration of the query, which makes the erratic behaviour is much less likely, but could still cause breakage when device disappear while apcupsd has it opened. > > > > > I suspect that usb subsystem tried to destroy the device but some internal > > refcounting prevents it. Proper use of destroy_dev(_cb)(9) avoids > > the issue. > > --HPS
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