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Date: Sun, 31 Aug 2014 07:38:22 -0400 From: Tejun Heo <tj@...nel.org> To: David Herrmann <dh.herrmann@...il.com> Cc: "Luis R. Rodriguez" <mcgrof@...not-panic.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Dmitry Torokhov <dmitry.torokhov@...il.com>, falcon@...zu.com, Takashi Iwai <tiwai@...e.de>, arjan@...ux.intel.com, linux-kernel <linux-kernel@...r.kernel.org>, Oleg Nesterov <oleg@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, penguin-kernel@...ove.sakura.ne.jp, Joseph Salisbury <joseph.salisbury@...onical.com>, bpoirier@...e.de, "Luis R. Rodriguez" <mcgrof@...e.com>, Rusty Russell <rusty@...tcorp.com.au> Subject: Re: [RFC v1 0/3] driver-core: add asynch module loading support (cc'ing Rusty for module loading) Hello, On Sun, Aug 31, 2014 at 01:25:03PM +0200, David Herrmann wrote: > On Sun, Aug 31, 2014 at 1:02 PM, Tejun Heo <tj@...nel.org> wrote: > > @@ -689,9 +704,23 @@ int bus_add_driver(struct device_driver *drv) > > > > klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); > > if (drv->bus->p->drivers_autoprobe) { > > - error = driver_attach(drv); > > - if (error) > > - goto out_unregister; > > + struct driver_attach_work *daw; Oops, this probably should go inside the below if block. > > + > > + if (drv->owner) { > > + daw = kzalloc(sizeof(*daw), GFP_KERNEL); > > + if (!daw) { > > + error = -ENOMEM; > > + goto out_unregister; > > + } > > + > > + INIT_WORK(&daw->work, driver_attach_workfn); > > + daw->driver = drv; > > + queue_work(driver_attach_wq, &daw->work); > > Doesn't this break on-demand cdev initialization? We currently call > request_module() on open() for unclaimed major/minor combinations. If > driver_attach() is no longer part of module_init(), there is no > guarantee the driver created the cdev before request_module() returns. Right, yeah, this really looks like something we'd need to switch per insmod instance. It looks like driver core needs a generic parameter to tell it to whether drive probing asynchronously to module loading or not. Maybe we can add a generic driver param like "driver_async_probe"? > I actually like this "deferred attach" approach, so this is not meant > as counter-argument. We just need to make sure to have a notion of > "settled modules" so we know how long to wait after loading a module. Another way could be making module-generic pollable file in the module's sysfs dir to indicate "full init completion", which would map to probing completion for drivers; however, given that we need to keep the synchronous behavior by default for compatibility, I don't think that buys us much. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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