- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Difference between seq_release and single_release ?
by Abhijeet Kasurde April 24, 2014

April 24, 2014

Hi All, What is difference between seq_release and single_release API ? Can someone explain particular use case of these APIs ? Thanks, Abhijeet Kasurde

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ioperm and iopl
by Adil Mujeeb April 24, 2014

April 24, 2014

Hi list, Are we going to remove the support of ioperm and iopl system call in future kernel release? I heard it but not sure if its already removed or candidate for removal. Regards, Adil

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"Time police" - best way to submit?
by Henry Hallam April 23, 2014

April 23, 2014

Hi, my name is Henry and I'm a kernel newbie. Recently plagued by a perplexing issue where *something* would step the clock on an important server by exactly 5 minutes at infrequent, unpredictable intervals, I put together my first kernel module - a trivial hook into do_settimeofday via a jprobe, that prints the PID, process name and time adjustment to the kernel message log. Here's what I have so far: https://github.com/henryhallam/timepolice Questions: 1. Is a module using kprobes/jprobes the right way to do it, vs adding printks to linux/time/timekeeping.c? 2. If a module is the way to go, would it be better to create a read/write /proc entry to allow enabling and disabling, rather than inserting the module to enable and removing to disable? 3. Is this sort of thing worth submitting to mainline? What are the next steps for that, after choosing a better name, changing the silly load/unload messages and ensuring it passes checkpatch.pl? Thanks!

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Kernel Projects
by Julio Faracco April 23, 2014

April 23, 2014

Hi, Does anybody know if there is a program to offer small (or big) kernel projects to students or someone who are interested in? I'm looking for programs like Google Summer of Code or http://kernelnewbies.org/KernelProjects I'm interested to contribute with kernel patches, but I don't know how and where to start it. I will be glad if someone give me ideas and/or suggestions. Thanks! *--* *Julio Cesar Faracco* *University of São Paulo - Brazil*

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a question about __nocache_pa macro
by Chan Kim April 23, 2014

April 23, 2014

Hi, can someony explain this macro to me? It's in arch/sparc/include/asm/pgtsrmmu.h (linux 3.3) #define __nocache_pa(VADDR) (((unsigned long)VADDR) - SRMMU_NOCACHE_VADDR + __pa((unsigned long)srmmu_nocache_pool)) it looks like converting virtual address VADDR to physical address for which no cache is used. so I can see SRMMU_NOCACHE_VADDR is the virtual address start value from which no cache is used(in our case it's 0xc8000000), and VADDR is relative to this start location (thus the minus). But why do we add the last srmmu_nocache_pool term? we are adding the offset to physical nocache pool address. So it seems like it is converting a virtual address to a physcal address relative to nocache pool.. Why is it done this way? Thanks in advance. Chan

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pft not found for mmtest.
by Raju April 22, 2014

April 22, 2014

Hi all, May I know from where I can download pft. As pft is not found in http://mcp/mmtests-mirror/pft/ <http://mcp/mmtests-mirror/pft//pft-0.12x.tar.gz> and http://free.linux.hp.com/~lts/Tools/ <http://free.linux.hp.com/%7Elts/Tools/pft-0.12x.tar.gz> Log while running mmtest pft-install: Fetching from mirrorhttp://mcp/mmtests-mirror/pft//pft-0.12x.tar.gz <http://mcp/mmtests-mirror/pft//pft-0.12x.tar.gz> pft-install: Fetching from internethttp://free.linux.hp.com/~lts/Tools/pft-0.12x.tar.gz <http://free.linux.hp.com/%7Elts/Tools/pft-0.12x.tar.gz> FATAL pft-install: pft-install: Could not downloadhttp://free.linux.hp.com/~lts/Tools/pft-0.12x.tar.gz <http://free.linux.hp.com/%7Elts/Tools/pft-0.12x.tar.gz> FATAL pft-bench: pft install script returned error FATAL: pft returned failure, unable to continue test exit :: pft 255 Regards

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mmtest is failed as pft is not found
by Hariharan T.S April 22, 2014

April 22, 2014

Hi All, mmtest fails with the following error. The pft (Page fault is not found in any of the locations show below. pft-install: Fetching from mirror http://mcp/mmtests-mirror/pft//pft-0.12x.tar.gz pft-install: Fetching from internet http://free.linux.hp.com/~lts/Tools/pft-0.12x.tar.gz FATAL pft-install: pft-install: Could not download http://free.linux.hp.com/~lts/Tools/pft-0.12x.tar.gz FATAL pft-bench: pft install script returned error FATAL: pft returned failure, unable to continue test exit :: pft 255 May I know from where I can download or find pft. Thanks Hariharan T S

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cgroups: cannot write on file memory.oom_control
by Hedi Boufaied April 22, 2014

April 22, 2014

Hi everyone, I am working with cgroups on OpenSuse (over VirtualBox) and I cannot disable the OOM killer by writing to the file memory.oom_control: > echo 1 > memory.oom_control > -bash: echo: write error: Invalid argument I can change the memory limit and several other settings by writing to the appropriate files (like memory.limit_in_bytes) but I could never write to file memory.oom_control although I am root. I saw someone posted a similar issue a few days ago but there was no reply... I have copied below the sequence of command I am using. Any idea what could be the issue ? Thanks in advance for your help! Hedi ---- /sys/fs> su - root /sys/fs> cd cgroup /sys/fs/cgroup> cgcreate -g memory:/mygroup /sys/fs/cgroup> cd memory/mygroup /sys/fs/cgroup/memory/mygroup> echo 32M > memory.limit_in_bytes /sys/fs/cgroup/memory/mygroup> cat memory.limit_in_bytes 33554432 /sys/fs/cgroup/memory/mygroup> echo 1 > memory.oom_control -bash: echo: write error: Invalid argument /sys/fs/cgroup/memory/mygroup> cat memory.oom_control oom_kill_disable 0 under_oom 0 ---

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Hi, a question about sending patches to lkml
by Jianyu Zhan April 22, 2014

April 22, 2014

Hi,all I have a pile of patches to send. It involves several subsystems, but not all patches are all subsystem related. So 1) should I send all emails to all subsytems or just 2) send the related ones to correspoding mail-list and all to lkml. I am now using git-send-email, it seems it choose 1). Any suggestion? I think 1) is good, by maybe to noisy for those who only cares their subsys-related parts. Thanks, Jianyu Zhan

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slicoss: a hardware debugging question
by David Matlack April 22, 2014

April 22, 2014

I've been working on the staging slicoss driver (for an ethernet NIC). I haven't been able to find any detailed documentation about the card online, all I have is the source code. During the PCI probe routine slic_entry_probe(), the driver attempts to load some configuration data from the card. The driver disables interrupts from the deviece and polls the ISR which signals the completed transfer. The relevant code is in drivers/staging/slicoss/slicoss.c:slic_card_init: [...] slic_config_get(adapter, phys_configl, phys_configh); for (;;) { if (adapter->pshmem->isr) { [...] } else { mdelay(1); i++; if (i > 5000) { dev_err(&adapter->pcidev->dev, "%d config data fetch timed out!\n", adapter->port); [...] } } } [...] The only problem is, this times out more than half the time. And when it succeeds, it [seemingly] always takes 22 cycles. I have tried increasing 5000 to various higher numbers (up to 50000) with no effect. I thought it might be a compiler optimization or coherence issue so I threw a mb() in the loop and that seemed to have no effect as well. Any recommendations on debugging? Thanks. --David

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