June 2016 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

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

1 0

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?

3 2

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

5 4

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.

1 1

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

3 2

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 ========================================================================

1 0

[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 ========================================================================

1 0

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

4 3

want to clarify a couple things about initramfs
by Robert P. J. Day June 20, 2016

June 20, 2016

for the first time, i'm going to dive into the kernel support for initramfs, so i'll start with a couple questions. first, i note that the Doc file ramfs-rootfs-initramfs.txt seems(?) a bit dated, in that it refers to the 2.6 kernel, but it may just mean that it's relevant for 2.6 and everything newer, so it may be just fine, i guess i'll find out eventually. next (and possibly a silly question), i know that the primary(?) purpose of an initramfs is to load an early rootfs to get access to kernel modules, after which one tosses away the initramfs and mounts the "real" rootfs. but i'm pretty sure i have the right to build a kernel with enough of an initramfs that i can run off that embedded initramfs entirely out of RAM if all i want to do is, say, basic diagnostics. next, from the Doc file, i see the possibility of a second (external) initramfs: External initramfs images: -------------------------- If the kernel has initrd support enabled, an external cpio.gz archive can also be passed into a 2.6 kernel in place of an initrd. In this case, the kernel will autodetect the type (initramfs, not initrd) and extract the external cpio archive into rootfs before trying to run /init. This has the memory efficiency advantages of initramfs (no ramdisk block device) but the separate packaging of initrd (which is nice if you have non-GPL code you'd like to run from initramfs, without conflating it with the GPL licensed Linux kernel binary). It can also be used to supplement the kernel's built-in initramfs image. The files in the external archive will overwrite any conflicting files in the built-in initramfs archive. Some distributors also prefer to customize a single kernel image with task-specific initramfs images, without recompiling." is all that still accurate? again, i'm sure i can confirm that once i start digging through the code. in my case, i don't think i'll need an external initramfs if i can cram everything i need into the one embedded in the kernel. thoughts? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

2 1

Coding style quesion
by Nicholas Mc Guire June 18, 2016

June 18, 2016

HI ! Stumbled across the somewhat inconsistent treatement of functions returning ERR_PTR() in the kernel with respect to coding style, while trying to write some static code checks. The two forms which seem comon are: if (PTR_ERR(var) == -EINVAL) { and if (var == ERR_PTR(-EINVAL)) { of which I think the first is the intended construct. my understanding of ERR_PTR is that it is intended to be used in the form ret = ERR_PTR(-EINVAL); ... retrurn ret; or return ERR_PTR(-EINVAL); but not as in the second if() above - technically its the same thing Is there an "official" preference to the one or other form ? thx! hofrat

1 0