Dear. Chris. kernel is blocking during 5sec included mmc initializing by root_delay. I think root_wait is better the solution than rootdelay. Thanks for your advice. 2011/3/30 Chris Ball <cjb@xxxxxxxxxx>: > Hi, > > On Tue, Mar 29 2011, NamJae Jeon wrote: >> Dear. Chris, Ben. >> >> Thanks for your reply. >> >> As you know, booting time is important factor in embededd device. >> >> If rootdelay is set to 5, kernel will be waiting for 5 sec. root_wait >> is also looping per 100ms. > > No. It will wait for *up to* five seconds, but it will actually > continue as soon as the device has enumerated. Same with rootwait, > of course. > > MMC is by no means the only subsystem that behaves this way. If you > were using a USB or SATA/AHCI device, amongst many others, you would > have exactly the same problem. > > You can see http://lwn.net/Articles/330378/ for some background reading. > >> I have a question. Why is mmc using delayed workqueue ? > > So that device enumeration can happen in the background, without > delaying the kernel boot while we wait for the controller to get all > the way to creating partitions. > > If we didn't use a workqueue and you were working on an embedded project > that had an MMC slot that it *didn't* boot from, you'd be yelling at us > for instead wasting time holding up your non-mmc boot by not letting > userspace get going until we list MMC partitions. We can't win. :-) > > In any case, I suspect that your system actually does boot faster than > it would if we didn't use a workqueue -- this way the delays in waiting > for the controller to come up are parallelized with other boot code. > That's good, right? > > - Chris. > -- > Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/> > One Laptop Per Child > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
