On Sun, 10 Feb 2008 12:58:09 +0100 Eric Piel wrote: > (adding some CC's) > Christoph Hellwig wrote: > > On Sun, Feb 10, 2008 at 08:12:26AM +0100, Christoph Hellwig wrote: > >> Folks, moving this call around hidden behing in completely unreviewed > >> acpi junk is not acceptable. > >> > >> Either populate_rootfs _is_ safe to be called earlier and then we should > >> do it always or it's not. Either way such a change should be posted > >> separately and reviewd on lkml. > Hi, > > I agree with you, the order of the initialization should not be changed > by some config options. Either it works, or it doesn't! So the question > now is : "is fine to move populate_rootfs() earlier?" > > Some data points: > * It used to be called earlier. It was moved to be called later about a > year ago by Linus (8d610dd52dd1da696e199e4b4545f33a2a5de5c6) with this log: > > Make sure we populate the initroot filesystem late enough > > > > We should not initialize rootfs before all the core initializers have > > run. So do it as a separate stage just before starting the regular > > driver initializers. > So there must be some good reasons to keep it late enough... > > * This patch is used in SuSE, and it seems noone has ever had a problem > with the initramfs early init. > > I guess the problem that Linus solved by moving populate_rootfs() > happens only rarely or on only few configurations. Linus, do you > remember what kind of problem it was? How can I reproduce it?
AFAIR the problem was that the kernel was trying to exec /sbin/hotplug before some kernel subsystems (e.g., pipe support) were completely initialized, which caused oopses during boot. Initramfs images generated by distro tools usually do not contain /sbin/hotplug, and therefore avoid the problem. (The kernel might also call /sbin/modprobe by itself, but it either does not do it during early boot, or /sbin/modprobe does not use kernel features which had not been initialized yet). > One different solution that I implemented [1] was to have an > "early_populate_rootfs()" before the acpi_early_init(), leaving > populate_rootfs() at the normal place. If the early version fails, it's > ok: we can't override the DSDT, but the later version will work as usual > anyway. This solution also seems to work quite often (it's used in > Ubuntu, Mandriva and PCLinuxOS) This would not solve the problem, because /sbin/hotplug (if present in the initramfs image) will exist too early. > Would that seem an acceptable solution? Or what other way exists? Disabling call_usermodehelper() until all core initializers had completed would fix the problem too; will such change be acceptable?
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