embedded-system-software-note.txt

embedded-system-software-note.txt

Process Context : context of kernel flow through system call of user process
Interrupt Context : context of kernel flow through interrupt by I/O devices.

Kernel Control Flow
 - Process Context (by system call)
 - Interrupt Context (by interrupt)
 
 kmalloc GFP_KERNEL
 sleep 
 
 In interrupt context, GPF_KERNEL cannot be used. (Because, sleeping is not accepted in interrupt context.)
 
 
 malloc
 ----------
 kmalloc
 get_alloc_page
 buddy, slab (2^N)
 
 jiffies
 high resolution tiemr
 
 
 signal handler
 -------
 for process
 in multi-thread, handler is executed on one thread.
 executing in user stack.
 mutex cannot be used! (handler is executed on a thread which already acquires the mutex)