Date: Sun, 28 Aug 2011 12:25:51 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: freebsd-arch@FreeBSD.org, Hans Petter Selasky <hselasky@FreeBSD.org> Subject: Re: skipping locks, mutex_owned, usb Message-ID: <4E5A099F.4060903@FreeBSD.org> In-Reply-To: <4E53986B.5000804@FreeBSD.org> References: <4E53986B.5000804@FreeBSD.org>
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on 23/08/2011 15:09 Andriy Gapon said the following:
> This "XXX cludge" [sic] pattern is scattered around a few functions in the ukbd
> code and perhaps other usb code:
> func()
> {
> if (!mtx_owned(&Giant)) {
> mtx_lock(&Giant);
> func();
> mtx_unlock(&Giant);
> return;
> }
>
> // etc ...
> }
Ohhh, nothing seems simple with the USB code:
/* make sure that the BUS mutex is not locked */
drop_bus = 0;
while (mtx_owned(&xroot->udev->bus->bus_mtx)) {
mtx_unlock(&xroot->udev->bus->bus_mtx);
drop_bus++;
}
/* make sure that the transfer mutex is not locked */
drop_xfer = 0;
while (mtx_owned(xroot->xfer_mtx)) {
mtx_unlock(xroot->xfer_mtx);
drop_xfer++;
}
So many unconventional tricks.
--
Andriy Gapon
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