I have a vmlinux ELF image which includes the initramfs image(kernel and root file system-RFS) which I would like to modify. I would like to add a new file to RFS.
I manage to get kernel and RFS part from vmlinux images. When RFS part is changed, below warning messages is seen

WARNING: at kernel/rcutree.c:2032 0x80512810()
Modules linked in:
Call Trace:[<800277f0>] 0x800277f0
[<8043fa90>] 0x8043fa90
[<8043fa90>] 0x8043fa90
[<800265dc>] 0x800265dc
[<80512810>] 0x80512810
[<80026620>] 0x80026620
[<800bdb8c>] 0x800bdb8c
[<80512810>] 0x80512810
[<80512908>] 0x80512908
[<80509758>] 0x80509758
[<805090dc>] 0x805090dc
[<8042f99c>] 0x8042f99c

I believe that the size of the initramfs is embedded into the kernel.
Do I need to recompile the kernel any time when I make any changes on RFS?
is there any way to change RFS without compiling the kernel?