On Sat, 2 May 2009 13:55:45 -0400 (EDT) Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Sat, 2 May 2009, James Bottomley wrote: > > > OK, so in your scheme, I get why console devices: they need to be > > present early before we start dumping console output otherwise it > > can get lost. > > > > However, I don't see the need for either network or block. > > > > For network, the only early discovery use is net root (which can be > > done fully asynchronously) > > Are you referring to the "rootwait" kernel parameter? Is there a > reason why this is a boot-time parameter instead of always being > set? I mean, under what circumstances would you _not_ want to wait > until the root device is present? if you have an initrd ;-) > > Perhaps with some enterprise systems, it is preferred to have the > system fail with an explicit error message rather than wait > indefinitely... actually, in an enterprise system, you want to reboot. The bootloader might boot a different kernel the next time that is known to work. (for example, the current kernel might have been booted with the "once" grub option) > > > What I'm getting at is that I don't see the benefit of this in the > > light of Arjan's async boot system, which can also tell us when all > > discovery is complete ... what added benefit am I missing here? > > How does Arjan's async boot system tell use when all discovery is > complete? AFAICS, it only tells you when all its async tasks are > finished. But device discovery and registration sometimes use other > asynchronous techniques which Arjan's code is unaware of. > Examples: the USB khubd thread, the USB mass-storage scanning thread, > and the SCSI async-scanning thread. for normal device probing we already have infrastructure though... wait_for_device_probe, driver_probe_done and friends... (the scsi scanning thread is being converted to the async infrastructure btw) do we need to invent more ? -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
