- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

kernel memory allocation
by Amirali Shambayati June 3, 2011

June 3, 2011

Hello all, I just want to allocate memory for a struct instantiation. Would anyone guide me what arguments I should pass to "kmalloc_node"? Regards, -- Amirali Shambayati Bachelor Student Computer Engineering Department Sharif University of Technology Tehran, Iran

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Calling printk with locks held
by Neil Baylis June 2, 2011

June 2, 2011

I've just been told that it's not OK to call printk while holding a lock. This came as a surprise to me, as I've written thousands of lines of code that calls printk while holding multiple locks, and have not seen any problem. The only explanation I was given was that it can deadlock. Is this correct? I thought there were very few places where it was not safe to call printk. Neil Baylis

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Fwd: Check Kernel Memory Allocation
by Dev Null June 2, 2011

June 2, 2011

---------- Forwarded message ---------- From: Dev Null <devnullfin(a)gmail.com> Date: Tue, May 31, 2011 at 4:08 PM Subject: Check Kernel Memory Allocation To: kernelnewbies Newbies <kernelnewbies(a)nl.linux.org> Hello, I wanted to know how much kernel and userspace memory is available on the Linux system during run-time either by some C code or some procfile. Do you know how to do that? Thanks, Dev

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show_regs vs dump_stack in watchdog_timer_fn
by Daniel Baluta June 2, 2011

June 2, 2011

Hello, Why the stack isn't always dumped in watchdog_timer_fn ([1])? Registers content is useful, but without a stack trace it's very hard to find the task which caused system softlockup. thanks, Daniel. [1] http://lxr.linux.no/linux+v2.6.39/kernel/watchdog.c#L292

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Implementing RFC 6056
by Arjun S R June 2, 2011

June 2, 2011

Hi, I would like implement RFC 6506 in linux kernel. It seems no one has implemented it. Its mainly about Transport protocol port randomisation. The fixed order[sequence of predictable randomness] of allocation of ephemeral port to application on request can cause malicious users to hijack connections based on time spent by the tcp ip api in various states. I have read the standards and is willing to go forward. Please post comments. -- Arjun S R

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surviving in lkml
by Anuz Pratap Singh Tomar June 2, 2011

June 2, 2011

Hi list, This is an interesting story/presentation by an lkml regular, not technical but useful. https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B8baQh2S… Regards Anuz

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Clarification on memory mapping
by sandeep kumar June 1, 2011

June 1, 2011

Hi, I am new to kernel programming. Last few days i have been reading about memory management, memory mapping etc., But i could not put the things together. Here i need clarifications regarding the few things whether wat i understood is right or not. 1) Mapping means bringing a device memory which is not in the address space of kernel/user to its address space. ioremap() : 2) ioremap does mapping of a particular i/o device to kernel logical memory address. mmap() 3) mmap does the mapping of a device memory to user space virtual address. kmap() 4) gets a kernel virtual address of an allocated high memory page. 5) And finally memory mapping does a manipulation of a PTE. Tell if i have interpreted anything wrong and please correct me. Thank you -- With regards, Sandeep Kumar Anantapalli,

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picking an ARM board with jtag for debugging
by Christopher Harvey June 1, 2011

June 1, 2011

I'm looking for an ARM board with a cortex a9 mpcore with a good solution for jtag debugging under linux. I have a beagle and a pandaboard sitting in front of me, but the beagle only has cortex a8 and the pandboard jtag situation looks pretty dismal. (You need to buy and download a lot of software). Cost really isn't an issue, (under 1000$) but good gdb support is critical. I need jtag specifically because kgdb doesn't start up soon enough for me. Anybody here doing ARM linux development with jtag? thanks, -Chris

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How DMA transfers > 2MB are being performed?
by sandeep kumar June 1, 2011

June 1, 2011

Hi all A very limited (1-2MB) address space is mapped to dma_alloc() in ARM architecture..what if a DMA transfer of >2MB is needed at a time? As DMA transfer starts asynchronously..CPU relinquishes data buses..so CPU cant control. So the excess data which is >2MB will be overflown or lost..So how this large data transfers are being managed? -- With regards, Sandeep Kumar Anantapalli,

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Disabling nagle algorithm
by C K Kashyap June 1, 2011

June 1, 2011

Hi, Is setting *net.ipv4.tcp_low_latency to 1 the right way of disabling nagle's algorithm?* *Regards,* *Kashyap*

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