On Thu, Jun 18, 2009 at 02:46:30PM +0930, Rusty Russell wrote: > On Mon, 15 Jun 2009 10:24:39 pm Michael S. Tsirkin wrote: > > On Mon, Jun 15, 2009 at 08:08:18AM -0400, Gregory Haskins wrote: > > > Hmm. I understand what you are saying conceptually (i.e. the .text > > > could get yanked before we hit the next line of code, in this case the > > > "return 0"). However, holding a reference when you _know_ someone else > > > holds a reference to me says that one of the references is redundant. > > > In addition, there is certainly plenty of precedence for > > > module_put(THIS_MODULE) all throughout the kernel (including > > > module_put_and_exit()). Are those broken as well? > > > > Maybe not, but I don't know why. It works fine as long as you don't > > unload any modules though :) Rusty, could you enlighten us please? > > Yep, they're almost all broken. A few have comments indicating that someone > else is holding a reference (eg. loopback). > > But at some point you give up playing whack-a-mole for random drivers. > > module_put_and_exit() does *not* have this problem, BTW. > > Rusty. I see that, the .text for module_put_and_exit is never modular itself. Thanks, Rusty! BTW, Gregory, this can be used to fix the race in the design: create a thread and let it drop the module reference with module_put_and_exit. Which will work, but I guess at this point we should ask ourselves whether all the hearburn with srcu, threads and module references is better than just asking the user to call and ioctl. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
