I am using the Texas Instruments official Yocto SDK to build a complete BSP for the Beaglebone X-15 ( TI AM5728 Processor ). The entire SDK builds great for the MACHINE=am57xx-evm type from the SDK. Later SDKs include the MACHINE=beagle-x15, but I need this older version with Linux kernel 4.4. The Linux kerne…
Tag: linux-kernel
Is setting the linux memory to unlimit will have an adverse effect?
I am running MPI job in linux server. I got error: it means that my linux server have locked memory with 65M, but my job needed more memory. I think 2G should be emough. I have found a solution about ulimiting the memory: But i am worried that i will cause system crash or some bad things happen. so can
Detect if running on a device with heterogeneous CPU architecture
I’m very specific on this one. I need to know if the device has a CPU which has heterogeneous cores like ARM’s big.LITTLE technology, for instance, a set of 4 ARM Cortex-A53 + another set of 4 more powerfull ARM Cortex-A72, totaling 8 cores, basically 2 processors in the same chip. The processors …
How can I use the cat command to read from a character device with my own character device driver?
I am trying to write a simple read/write character driver for a beaglebone. One of the tasks is to be able to use the cat command to read from the device, but I am unable to do so. Here is the code for my read function for my character device driver located inside char_drvr.c: Read executes successfully (the …
Transition of multi-core processor from real mode to protected mode in Linux
I’m trying to learn more about operating systems and I am currently taking a look how the Linux kernel is loaded and initialized. Thanks to several related questions and this book, I was mostly able to understand how the transition from real mode to protected mode works. However, the one thing I donR…
Serial port hangs on close()
I developed this simple kernel module, which emulates a serial port by using a FIFO queue and a timer (read from hardware : out from the queue, write to hardware : insert in the queue). Source code is shown next. Then, I wrote a simple test-application which configures the port settings (baud rate, parity, st…
Does linux process VSZ equal 0 mean kernel space application?
I notice some process always have VSZ as 0 how to understand why they have 0 VSZ? Answer VSZ is the Virtual Memory Size. It includes all memory that the process can access, including memory that is swapped out, memory that is allocated, but not used, and memory that is from shared libraries. So, the top comma…
Linux CONFIG_PREEMPT_RT for a quad core ARM A53 (newbie doubts)
I would like to activate the PREEMPTion features of my Linux Kernel. To do that I should download the right patch matching the version of the kernel I am using and that I compiled (as explained here). The version of the kernel I have is the Linux version 4.9.0 (obtained just typing uname -a from the command l…
GDB: breakpoint in linux built-in module fails
I am debugging linux kernel using two virtual machines connected via serial port. Target machine awaits connection from remote gdb, by inserting kgdbwait() and kgdboc=ttyS0,115200 in the correct entry in /boot/grub/grub.cfg. In Host machine Symbols are read and I am supposed to be able to put breakpoints on f…
Fast method to get current time with nsec-resolution?
I try to get a time-information with a resolution of a few hundred nanoseconds (to do some bit-banging stuff on an Raspberry Pi). I tried with clock_gettime() which provides the required resolution in timespec.tv_nsec, but it is too slow. Even when I run my process on one separate core of the CPU exclusively …