tl;dr -> Provide a proper MVCE. This answer should be a comment but is too big to be posted as comment, so posting as answer instead: I had to fix a bunch of syntax errors (missing semicolons) and declare undefined variables. After fixing all those problems, the code did NOTHING (the program quit even prior … Read more
The quantum allocated for a particular process may vary: You can tune “slice” by adjusting sched_latency_ns and sched_min_granularity_ns, but note that “slice” is not a fixed quantum. Also note that CFS preemption decisions are based upon instantaneous state. A task may have received a full (variable) “slice” of CPU time, but preemption will be triggered … Read more
Device trees do not need to be compiled with “architecture-aware” tools. The dtc compiler on your ubuntu machine is probably current enough to compile your device tree. Or you can download the latest source and compile it yourself. The dtc compiler can be found here: https://git.kernel.org/pub/scm/utils/dtc/dtc.git There are some good documents in that package that … Read more
Not all virtual (linear) addresses must be mapped to anything. If the code accesses unmapped page, the page fault is risen. The physical page can be mapped to several virtual addresses simultaneously. In the 4 GB virtual memory there are 2 sections: 0x0… 0xbfffffff – is process virtual memory and 0xc0000000 .. 0xffffffff is a … Read more
I believe you are looking wrong at the problem – any update which is non atomic (e.g. dd a file system image, replace files in a directory) is broken by design – if the power goes off in the middle of an update the system is a brick and for embedded system, power can go … Read more
First, start by writing a generic kernel module. There are multiple places to look up for information but I found this link to be very useful. After you have gone through all examples specified there you can start writing your own Linux Driver Module. Please note, that you will not get away with just copy-pasting … Read more
**TODO** +editPic: Linux Kernel Developer -> (Ring Layer 0) +addSection: Kernel Virtualization Engine KERN_WARN_CODING_STYLE: Do not Loop unless you absolutely have to. Recommended Books for the Uninitialized void *i “Men do not understand books until they have a certain amount of life, or at any rate no man understands a deep book, until he has … Read more
Linux is a general-purpose OS (GPOS); its application to embedded systems is usually motivated by the availability of device support, file-systems, network connectivity, and UI support. All these things can be available in an RTOS, but often with less broad support, or at additional cost or integration effort. Many RTOS are not full OS in … Read more
asm volatile(“” ::: “memory”); creates a compiler level memory barrier forcing optimizer to not re-order memory accesses across the barrier. For example, if you need to access some address in a specific order (probably because that memory area is actually backed by a different device rather than a memory) you need to be able tell … Read more
What is the difference between them? Image: the generic Linux kernel binary image file. zImage: a compressed version of the Linux kernel image that is self-extracting. uImage: an image file that has a U-Boot wrapper (installed by the mkimage utility) that includes the OS type and loader information. A very common practice (e.g. the typical … Read more