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How to make linux stop all processes/activities except the one I am benchmarking?
by Lev Olshvang Oct. 8, 2018

Oct. 8, 2018

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Diploma project with the Linux kernel
by Boian Karatotev Oct. 5, 2018

Oct. 5, 2018

Hello, I am a Computer Science student and for my last year I need to make and present a 'diploma project' at the end of June. So far I want to make a kernel module, whose description is in the following paragraph. I feel comfortable with C and my OS knowledge is maybe slightly better than my OS course. My question is: Would it possible to pull this off? I have no experience with the kernel and I want to get into kernel development, so this would be a perfect opportunity for that. My only issue is that this may be too complex for my experience. My idea: Something along the lines of checkpoint-restart as a kernel module. I want to ultimately be able to migrate a running process to a different machine (assuming same at least some basic similarity). I know of BLCR <http://crd.lbl.gov/departments/computer-science/CLaSS/research/BLCR/> and I am planning on using it as a guide, although I am unsure about working on it directly. As far as I know, the grading process does not require this to be 100% complete, so I am aiming at transferring at least all the memory, restoring file descriptors and maybe child processes/threads. I will really appreciate any feedback! Cheers, Boyan

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How to enable max98357a in sound/soc/codecs
by Paul Nader Oct. 4, 2018

Oct. 4, 2018

Hi, I'm trying to enable the max98357a codec in sound/soc/codecs. In the Kconfig file it is listed with an empty tristate so it doesn't show up when I do a make menu config. The only way I found so far was to patch the Kconfig and add a description to the tristate. It then appears in the menu when doing make menuconfig and it is also enabled if i patch my board's defconfig and add CONFIG_SND_SOC_MAX98357A=m to it. If I don't add a description then adding CONFIG_SND_SOC_MAX98357A=m doesn't enable it. How can I enable it without adding a description to the tristate? Thanks

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Forum registration activation broken?
by Paul Nader Oct. 4, 2018

Oct. 4, 2018

Hi, I registered to the forum this morning but it never sends any activation emails, maybe an admin could look into it? cheers

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style guide recommendations when including UAPI files?
by rpjday＠crashcourse.ca Oct. 3, 2018

Oct. 3, 2018

is there a strong (or even weak) style recommendation when including kernel header files under include/uapi in terms of explicitly including the "uapi" path component? i'm fully aware of the standard that most kernel code should include the "standard" kernel headers, such as: #include <linux/mii.h> where those headers are, of course, free to turn around and include the corresponding UAPI content; the above header file does indeed do just that: #include <linux/if.h> #include <uapi/linux/mii.h> however, in that very example, you can see the include of "linux/if.h" where there is, in fact, no header file include/linux/if.h, only include/uapi/linux/if.h. i can see from the top-level Makefile that that include will eventually pick up the UAPI version of the if.h header file: # Use USERINCLUDE when you must reference the UAPI directories only. USERINCLUDE := \ -I$(srctree)/arch/$(SRCARCH)/include/uapi \ -I$(objtree)/arch/$(SRCARCH)/include/generated/uapi \ -I$(srctree)/include/uapi \ -I$(objtree)/include/generated/uapi \ -include $(srctree)/include/linux/kconfig.h # Use LINUXINCLUDE when you must reference the include/ directory. # Needed to be compatible with the O= option LINUXINCLUDE := \ -I$(srctree)/arch/$(SRCARCH)/include \ -I$(objtree)/arch/$(SRCARCH)/include/generated \ $(if $(KBUILD_SRC), -I$(srctree)/include) \ -I$(objtree)/include \ $(USERINCLUDE) the point is, is that acceptable style? when i'm perusing kernel code and i see a reference to a header file <linux/if.h>, i simply assume it's a standard header file under include/, and i expect header files under the UAPI directory will explicitly say so in the include directive. thoughts? rday

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stack pointer used in vector_swi() in arm linux system call
by Anonymous Page Oct. 2, 2018

Oct. 2, 2018

Hi, While reading the vector_swi() routine for arm linux system call, I found that r0-r12 registers are copied to the kernel stack(below is the code). ENTRY(vector_swi) #ifdef CONFIG_CPU_V7M v7m_exception_entry #else sub sp, sp, #S_FRAME_SIZE stmia sp, {r0 - r12} @ Calling r0 - r12 As per my understanding, during system call arm enters into svc mode and jumps to vector_swi()routine and begins execution. The sp register of svc mode(sp_svc)points to kernel stack. r0-r12 registers are copied to the kernel stack. My question is how is the sp (sp_svc) register setup? How does it know the address of kernel stack? Is this kernel stack same as the process's(the process that called system call) kernel stack? Thanks & Regards

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Checkpatch.pl warning
by Shubham Singh Sept. 30, 2018

Sept. 30, 2018

Regarding the warning of checkpatch.pl, " 'str' object has no attribute 'decode' " This warning is related to spdxcheck.py which is because of version of python In python3 str has no attribute decode(), while it works fine in python2, without any warning. I checked the patch related to this https://lore.kernel.org/lkml/20180717190635.29467-1-jcline@redhat.com/T/#u We can resolve the warning by just putting an if statement above line.decode() to resolve the warning. Am I right or I missed something ? SHUBHAM SINGH @shubhsherl

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Linux FS design and implementation book
by inventsekar Sept. 29, 2018

Sept. 29, 2018

Hi All... Around last year I was searching for Linux Kernel FS design and implementation, and I found out a book by someone,.. a full length book, particularly, at the end of the book he/she included source code as well... unfortunately I forgotten the author of the book and the exact book name.. may i know if anybody remembers that book, please reply book name or the author name thank you.

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Problem with netconsole and eth0 timing
by don fisher Sept. 27, 2018

Sept. 27, 2018

I am trying to use netconsole to examine some problems I am having booting Alienware 13 r3 and 14 laptops. I am running opensuse 42.3 with generic 4.18.7 kernel configured to include netconsole. After building my kernel and including the proper command (as shown below) in the linux boot string: netconsole=64001@192.168.7.60/eth0,64001@192.168.7.55/34:e6:d7:01:2a:dd I receive the following error message, as shown by journalctl: sudo journalctl -b | grep netconsole Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: local port 64001 Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: local IPv4 address 192.168.7.60 Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: interface 'eth0' Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: remote port 64001 Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: remote IPv4 address 192.168.7.55 Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: remote ethernet address 34:e6:d7:01:2a:dd Sep 24 22:01:25 dfpc60 kernel: netpoll: netconsole: eth0 doesn't exist, aborting Sep 24 22:01:25 dfpc60 kernel: netconsole: cleaning up Sep 24 22:01:25 dfpc60 systemd-modules-load[185]: Module 'netconsole' is builtin I examined the timing in more detail and found that the above "eth0: doesn't exist" message comes at Sep 24 22:01:25.080603. The wicked message eth0: up comes at Sep 24 22:02:01.173616. The difference is maybe 36 seconds? There is an eth0: avail message at Sep 24 22:01:34.112744, don't know if that would suffice for netconsole Both are after netconsole has bailed out. Any obvious solutions I am missing? The documentation is pretty clear on how to set this up, so there must be some way to get it to work. I could find nothing on Google. This is my first post to this list, so if this question is not appropriate please let me know without flames:-) Don

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[PATCH] fix error handling in drivers/staging/rtl8192u/ieee80211/ieee80211_module.c
by valdis.kletnieks＠vt.edu Sept. 27, 2018

Sept. 27, 2018

John notes that if the kzalloc of ieee->pHTInfo fails, we fail to call ieee80211_networks_free(). In addition, that function has an un-needed check before kfree(). Reported-by: John Whitmore <arigead(a)gmail.com> Signed-off-by: Valdis Kletnieks <valdis.kletnieks(a)vt.edu> --- diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c b/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c index 90a097f2cd4e..97ff0371b5bb 100644 --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_module.c @@ -78,8 +78,6 @@ static inline int ieee80211_networks_allocate(struct ieee80211_device *ieee) static inline void ieee80211_networks_free(struct ieee80211_device *ieee) { - if (!ieee->networks) - return; kfree(ieee->networks); ieee->networks = NULL; } @@ -180,6 +178,7 @@ struct net_device *alloc_ieee80211(int sizeof_priv) return dev; failed: + ieee80211_networks_free(ieee); if (dev) free_netdev(dev);

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