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confused about use of "INITRD_COMPRESS" lines in top-level Makefile
by Robert P. J. Day June 22, 2016

June 22, 2016

currently poring over the initramfs code, and i'm a bit curious about the following. in usr/Kconfig, all the possible compression protocols can be selected, and by default are: config RD_GZIP bool "Support initial ramdisks compressed using gzip" default y select DECOMPRESS_GZIP help Support loading of a gzip-encoded initial ramdisk or cpio buffer. If unsure, say Y. config RD_BZIP2 bool "Support initial ramdisks compressed using bzip2" default y select DECOMPRESS_BZIP2 help Support loading of a bzip2-encoded initial ramdisk or cpio buffer. If unsure, say N. ... etc etc ... but in the top-level Makefile, here are the lines that ostensibly select which compression to actually use: # Select initial ramdisk compression format, default is gzip(1). # This shall be used by the dracut(8) tool while creating an initramfs image. # INITRD_COMPRESS-y := gzip INITRD_COMPRESS-$(CONFIG_RD_BZIP2) := bzip2 INITRD_COMPRESS-$(CONFIG_RD_LZMA) := lzma INITRD_COMPRESS-$(CONFIG_RD_XZ) := xz INITRD_COMPRESS-$(CONFIG_RD_LZO) := lzo INITRD_COMPRESS-$(CONFIG_RD_LZ4) := lz4 # do not export INITRD_COMPRESS, since we didn't actually # choose a sane default compression above. # export INITRD_COMPRESS := $(INITRD_COMPRESS-y) so as i read this, the single compression protocol selected will be the last one configured in that list, but where is that variable eventually used? where is the build code or utility that examines the value eventually set and invokes dracut, as the comment suggests? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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oh yeah
by ty armour June 21, 2016

June 21, 2016

if you all want to you can build computers microchip by microchip, just post tutorials on it if you do! these are fun things to think about. IM like a few years out but im sure ill get it done

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cool
by ty armour June 21, 2016

June 21, 2016

yeah ill take a read through them. I am working on building my own computers and cnc machines either analog or microchip by microchip and im sure these will help me. ill figure it out but yeah also look for analog computers in a few years. thanks

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boot param to change tick
by Lax Clarke June 21, 2016

June 21, 2016

Is there a way to change a grub/lilo kernel boot param to change the kernel tick rate?

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looking for tutorials
by ty armour June 21, 2016

June 21, 2016

I need tutorials on kernel development. And on complete operating system development. I would prefer them to be in assembly because it is faster, but it seriously needs to get done. If you are interested, simply post all of the tutorials and other relevant information to coding kernels that you can and show the references, like actually say okay so in order to do this we need to look for this in the assembler manual. Thanks and have fun

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IPV6 Multipath support
by Narasimha M June 21, 2016

June 21, 2016

Hi All, I am using linux kernel 3.10.20, and tried to add multipath routes using the below commands. ip -6 route add default nexthop via 2222::1 dev eth1 weight 1 nexthop via 3333::2 dev eth0 weight 1. But when i run the traffic to the host reachable to both the interfaces, traffic is always going through eth1, which means the multipath routing is not working. Could you please let us know that do we have multipath support for ipv6 in linux3.10.20 kernel ? Thanks in advance.

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Call Trace analysis doubt
by Muni Sekhar June 21, 2016

June 21, 2016

Hi, Let’s assume WARNING message says something like: [ 0.000000] Call Trace: [ 0.000000] [<ffffffff81762590>] dump_stack+0x45/0x56 [ 0.000000] [<ffffffff8106dd2d>] warn_slowpath_common+0x7d/0xa0 [ 0.000000] [<ffffffff8106dde4>] warn_slowpath_fmt_taint+0x44/0x50 [ 0.000000] [<ffffffff8143329c>] ? acpi_tb_acquire_table+0x3e/0x6c [ 0.000000] [<ffffffff81765070>] warn_invalid_dmar+0x81/0x93 [ 0.000000] [<ffffffff81d8989d>] detect_intel_iommu+0xe9/0x172 [ 0.000000] [<ffffffff81d3c84f>] pci_iommu_alloc+0x4a/0x6c [ 0.000000] [<ffffffff81d4cb4b>] mem_init+0x17/0x9c [ 0.000000] [<ffffffff81d31e80>] start_kernel+0x23b/0x47d [ 0.000000] [<ffffffff81d31a4e>] ? set_init_arg+0x53/0x53 [ 0.000000] [<ffffffff81d31120>] ? early_idt_handlers+0x120/0x120 [ 0.000000] [<ffffffff81d315ee>] x86_64_start_reservations+0x2a/0x2c [ 0.000000] [<ffffffff81d31733>] x86_64_start_kernel+0x143/0x152 [ 0.000000] ---[ end trace c32c0e307381ad8a ]--- Few symbols in the above mentioned call trace are prefixed with “?” (for e.g. ?early_idt_handlers\? set_init_arg\? acpi_tb_acquire_table), what does it mean? Does it needs to be considered while debugging the kernel module? Call Trace shows “function+0xoffset/0xlength”. Does the 0xoffset/0xlength changes if the module is built with –g option and without –g option? Thanks in Advance, -- Thanks, Sekhar

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coding style: "obj-y" versus "obj-$(CONFIG_FOO)"?
by Robert P. J. Day June 20, 2016

June 20, 2016

a bit more pedantry ... in init/Makefile, i see this test: ifneq ($(CONFIG_BLK_DEV_INITRD),y) obj-y += noinitramfs.o else obj-$(CONFIG_BLK_DEV_INITRD) += initramfs.o endif which is perfectly correct, but since BLK_DEV_INITRD is defined as a boolean, it can be assigned only yes or no, so is there any reason that second assignment wasn't written simply as: obj-y += initramfs.o sure, it's picky, but whenever i see Makefile content of the form: obj-$(CONFIG_FOO) i take into account that that could be a tristate setting. if it isn't, it just makes more sense aesthetically to me to use "obj-y" for clarity. is there a coding style note about this sort of thing? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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[PATCH] Small number of aesthetic/dependency cleanups in usr/Kconfig
by Robert P. J. Day June 20, 2016

June 20, 2016

* Remove superfluous dependencies on BLK_DEV_INITRD. * Couple grammar fixes. * Add proper hyphenation. * Add periods at end of some help sentences. Signed-off-by: Robert P. J. Day <rpjday(a)crashcourse.ca> --- only place i'm not absolutely confident is the removal of those dependency lines but, AFAICT, this Kconfig file is sourced only from init/Kconfig, which contains: if BLK_DEV_INITRD source "usr/Kconfig" endif so unless that Kconfig file is sourced from elsewhere, this should be fine. diff --git a/usr/Kconfig b/usr/Kconfig index 572dcf7..392021d 100644 --- a/usr/Kconfig +++ b/usr/Kconfig @@ -26,7 +26,7 @@ config INITRAMFS_ROOT_UID depends on INITRAMFS_SOURCE!="" default "0" help - This setting is only meaningful if the INITRAMFS_SOURCE is + This setting is only meaningful if the INITRAMFS_SOURCE contains a directory. Setting this user ID (UID) to something other than "0" will cause all files owned by that UID to be owned by user root in the initial ramdisk image. @@ -38,7 +38,7 @@ config INITRAMFS_ROOT_GID depends on INITRAMFS_SOURCE!="" default "0" help - This setting is only meaningful if the INITRAMFS_SOURCE is + This setting is only meaningful if the INITRAMFS_SOURCE contains a directory. Setting this group ID (GID) to something other than "0" will cause all files owned by that GID to be owned by group root in the initial ramdisk image. @@ -47,54 +47,48 @@ config INITRAMFS_ROOT_GID config RD_GZIP bool "Support initial ramdisks compressed using gzip" - depends on BLK_DEV_INITRD default y select DECOMPRESS_GZIP help - Support loading of a gzip encoded initial ramdisk or cpio buffer. + Support loading of a gzip-encoded initial ramdisk or cpio buffer. If unsure, say Y. config RD_BZIP2 bool "Support initial ramdisks compressed using bzip2" default y - depends on BLK_DEV_INITRD select DECOMPRESS_BZIP2 help - Support loading of a bzip2 encoded initial ramdisk or cpio buffer + Support loading of a bzip2-encoded initial ramdisk or cpio buffer. If unsure, say N. config RD_LZMA bool "Support initial ramdisks compressed using LZMA" default y - depends on BLK_DEV_INITRD select DECOMPRESS_LZMA help - Support loading of a LZMA encoded initial ramdisk or cpio buffer + Support loading of a LZMA-encoded initial ramdisk or cpio buffer. If unsure, say N. config RD_XZ bool "Support initial ramdisks compressed using XZ" - depends on BLK_DEV_INITRD default y select DECOMPRESS_XZ help - Support loading of a XZ encoded initial ramdisk or cpio buffer. + Support loading of a XZ-encoded initial ramdisk or cpio buffer. If unsure, say N. config RD_LZO bool "Support initial ramdisks compressed using LZO" default y - depends on BLK_DEV_INITRD select DECOMPRESS_LZO help - Support loading of a LZO encoded initial ramdisk or cpio buffer + Support loading of a LZO-encoded initial ramdisk or cpio buffer. If unsure, say N. config RD_LZ4 bool "Support initial ramdisks compressed using LZ4" default y - depends on BLK_DEV_INITRD select DECOMPRESS_LZ4 help - Support loading of a LZ4 encoded initial ramdisk or cpio buffer + Support loading of a LZ4-encoded initial ramdisk or cpio buffer. If unsure, say N. -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Use of list_head struct
by Martin Houry June 20, 2016

June 20, 2016

Hello mailing list! I've read some code in the NFS4.1 client. I have trouble to access variables in a list_head. So I have : (include/linux/sunrpc/xprt.h line 168) struct rpc_xprt{ . . struct rpc_wait_queue pending; /* requests in flight */ . . } ==> struct rpc_wait_queue { . struct list_head tasks[RPC_NR_PRIORITY]; /* task queue for each priority level */ . } The struct "list_head" is a classical linked list. But How do I know the type of the struct in this list? I can maybe guess the struct in it : struct rpc_task {} But how can I be certain that "struct list_head tasks" contains some "struct rpc_task"? I'm new here, thank you for your help! Martin

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