Sorry for the delay, I can't be responsive these days... On 07/27, Michael S. Tsirkin wrote: > > On Mon, Jul 26, 2010 at 08:08:34PM +0200, Oleg Nesterov wrote: > > On 07/26, Sridhar Samudrala wrote: > > > > > > I have been testing out a similar patch that uses kernel_thread() without CLONE_FILES > > > flag rather than create_kthread() and then closing the files. > > > > !CLONE_FILES can't help. copy_files() does dup_fd() in this case. > > The child still inherits the files. > > > > > Either version should be fine. > > > > I think neither version is fine ;) > > > > exit_files() is not enough too. How about the signals, reparenting? > > > > > > I already forgot all details, probably I missed somethig. But it > > seems to me that it is better to just export get/set affinity and > > forget about all complications. > > > > Oleg. > > Oleg, so can I attach your Ack to the patch in question, and merge > it all through net-next? Well, I do not think you need my ack ;) But I must admit, I personally dislike this idea. A kernel thread which is the child of the user-space process, and in fact it is not the "real" kernel thread. I think this is against the common case. If you do not care the signals/reparenting, why can't you fork the user-space process which does all the work via ioctl's ? OK, I do not understand the problem domain, probably this can't work. Anyway, the patch looks buggy to me. Starting from create_kthread(&create); wait_for_completion(&create.done); At least you should check create_kthread() suceeds, otherwise wait_for_completion() will hang forever. OTOH, if it suceeds then wait_for_completion() is not needed. But this is minor. create_kthread()->kernel_thread() uses CLONE_VM, this means that the child will share ->mm. And this means that if the parent recieves the coredumping signal it will hang forever in kernel space waiting until this child exits. This is just the immediate surprise I can see with this approach, I am afraid there is something else. And once again. We are doing this hacks only because we lack a couples of exports (iiuk). This is, well, a bit strange ;) Oleg. -- 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
