On Thu, Feb 26, 2015 at 07:46:38AM -0500, John Baldwin wrote: > On Thursday, February 26, 2015 12:40:06 AM Mateusz Guzik wrote: > > On Fri, Feb 06, 2015 at 04:09:02PM +0000, John Baldwin wrote: > > > Author: jhb > > > Date: Fri Feb 6 16:09:01 2015 > > > New Revision: 278320 > > > URL: https://svnweb.freebsd.org/changeset/base/278320 > > > > > > Log: > > > Add a new device control utility for new-bus devices called devctl. > > > This > > > allows the user to request administrative changes to individual devices > > > > [..] > > > > > +static int > > > +devctl2_ioctl(struct cdev *cdev, u_long cmd, caddr_t data, int fflag, > > > + struct thread *td) > > > +{ > > > + struct devreq *req; > > > + device_t dev; > > > + int error, old; > > > + > > > + /* Locate the device to control. */ > > > + mtx_lock(&Giant); > > > + req = (struct devreq *)data; > > > > [..] > > > > > + switch (cmd) { > > > > [..] > > > > > + case DEV_SET_DRIVER: { > > > + devclass_t dc; > > > + char driver[128]; > > > + > > > + error = copyinstr(req->dr_data, driver, sizeof(driver), NULL); > > > > [..] > > > > > + if (!driver_exists(dev->parent, driver)) { > > > + error = ENOENT; > > > + break; > > > + } > > > > [..] > > > > > + } > > > + mtx_unlock(&Giant); > > > + return (error); > > > +} > > > > I only skimmed thourgh this, will not a page fault drop + reacquire Giant > > lock? > > > > iow, would not it be better to copy prior to taking the lock? > > It won't make a difference. All the logic is done after the copy, so it is > still atomic. >
Are devices guaranteed to be persistent? find_device does ref them in any way, so i would assume that the dev you found is only stable as long as Giant lock is held. -- Mateusz Guzik <mjguzik gmail.com> _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
