January 2015 - kernelnewbies@kernelnewbies.org

linux-tools perf for ARM boards.
by Anand Moon Jan. 25, 2015

Jan. 25, 2015

hi All, Could some body point me method to install linux/tools/perf on ARM boards. I have enabled the support for perf in .config CONFIG_PERF_EVENTS=y CONFIG_HW_PERF_EVENTS=y root@odroid-xu3:/usr/src/odroidxu3-3.18.y/tools# make perf DESCEND lib/api MKDIR libapi_dirs CC fs/debugfs.o CC fs/fs.o CC fd/array.o AR libapikfs.a DESCEND perf BUILD: Doing 'make -j8' parallel build config/Makefile:613: No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev Auto-detecting system features: ... dwarf: [ on ] ... glibc: [ on ] ... gtk2: [ on ] ... libaudit: [ on ] ... libbfd: [ on ] ... libelf: [ on ] ... libnuma: [ OFF ] ... libperl: [ on ] ... libpython: [ on ] ... libslang: [ on ] ... libunwind: [ on ] ... libdw-dwarf-unwind: [ on ] ... DWARF post unwind library: libunwind SUBDIR /usr/src/odroidxu3-3.18.y/tools/lib/traceevent/ LINK perf LINK libperf-gtk.so GEN python/perf.so build is successful but how to install and where to install. -Anand Moon

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difference between struct proto and struct proto_ops
by nawab Jan. 25, 2015

Jan. 25, 2015

What is the difference between struct proto and struct proto_ops : Both are having the same functions:setsockopt,getsockopt,bind,connect etc... So which functions are called when we call connect ,bind from userspace....

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Hi , why the function smp_setup_processor_id is blank ?
by sizel Jan. 23, 2015

Jan. 23, 2015

Hi , i am a kernel_newbie. I am studing the start_kernel function why the function smp_setup_processor_id is blank in arm and x86 playform ? Thank you!

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Show kmem_cache in /proc/slabinfo
by nawab Jan. 22, 2015

Jan. 22, 2015

How can i show the cache created by using kmem_cache_create in /proc/slabinfo... If we have an constructor then i am able to have the cache in /proc/slabinfo... Without constructor can we do??

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Framebuffer Fonts
by Ssagarr Patil Jan. 22, 2015

Jan. 22, 2015

Hi All, I am working on a small oled display, which is implemented as Linux framebuffer driver. I want to write chars and wanted to see if there is a generic framebuffer library that can be used display the fonts. Any pointers on this would be helpful. Thanks & Regards, Sagar

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One question
by Meyer Lansky Jan. 22, 2015

Jan. 22, 2015

I continue to study the task scheduler O(1) I do not understand what makes this part of the code ? 1317 void kick_process(struct task_struct *p) 1318 { 1319 int cpu; 1320 1321 preempt_disable(); 1322 cpu = task_cpu(p); 1323 if ((cpu != smp_processor_id()) && task_curr(p)) 1324 smp_send_reschedule(cpu); 1325 preempt_enable(); link to source code : http://lxr.free-electrons.com/source/kernel/sched/core.c#L1317 what it means to do this function kick_process ? I just met her for the first time If you say I will be very grateful to you for your help

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PCIe bus enumeration
by J.Hwan Kim Jan. 22, 2015

Jan. 22, 2015

Hi, Is there any method for assigning PCIe bus fixed? For example, my device pcie bus number is changed when another pcie device is inserted. I have a 4 same pcie device and i want to identify each device according to the pci bus number (according to pcie slot they are inserted into). When i change kernel boot parameter for kernel to assign the pci bus number, the result was the same. Is there any method for that? Thanks in advance. Regards, J.Hwan Kim.

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examples of `<hardirq-safe> -> <hardirq-unsafe>`
by 孙建希 Jan. 22, 2015

Jan. 22, 2015

Hi, I am reading lockdep document. http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/Documentation/lo… Could anyone give me same dead lock examples of `<hardirq-safe> -> <hardirq-unsafe>`.

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confusion in interrup handler
by Er Krishna Jan. 22, 2015

Jan. 22, 2015

Hi All, Pls help me here to understand the following scenario: As we know, we cant sleep inside interrupt handler. But what is the reason for it? If I put sleep inside the handler code handler, handler code will not complete and none of the process on that particular processor will ever will execute. So it will be kind of deadlock. But what if the system is having multiple processors ? Is it safe here to sleep ? If not what is the reason ? Best regrads, Krishna

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Building Hello World LSM
by Thomas F. J.-M. Pasquier Jan. 21, 2015

Jan. 21, 2015

Hi everyone, Kernel version 3.17.8 I am trying to build a skeleton LSM module, but I am not having much luck so far. The problem seems to be that the LSM init function is never called. I am selecting my helloworld LSM when building the kernel and it is set as default (checked and re-checked in menuconfig + in the file). The build is going fine (my module is built as I would expect). The rest of the building procedure goes fine. I reboot, the new image works just fine except my LSM is not in (nor any other, it seems, for that matter). Here is the init function: static __init int hw_init(void){ /* avoid security registration races */ if (!security_module_enable(&hw_ops)){ printk(KERN_INFO "hw: Disabled at boot.\n"); return 0; } printk(KERN_INFO "hw: Initializing.\n"); if (register_security(&hw_ops)) panic("hw: Unable to register with kernel.\n"); else printk(KERN_INFO "hw: registered with the kernel.\n"); return 0; } security_initcall(hw_init); I looked at how it was done in SELinux and the other security module and I don't seem to be doing things differently or incorrectly. I checked the log level just in case and that's not the issue either. I am tempted to say the problem come from my building procedure/configuration, rather than the module/code in itself (the dist on top of the kernel is fedora21). I have been at it for a while now and any help would be most welcomed. Thank you in advance. Regards, Thomas

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