Shriramana Sharma wrote: > As I understand it, the kernel is always running Not in the same sense that a process is "running". Most of the time, it's "blocked" waiting for some external event to occur and give it something to do. > and whenever an app > asks for a system resource the kernel does the needful. However, in my > process tree I see no process named linux or kernel. I only see the init > process at the root of the tree. Does the init process represent the kernel? No. "init" is /sbin/init. It's a normal process, albeit a fairly important one. > When an app does a system call, would some form of IPC between the > process of that app and the kernel process (assuming there is one) be > involved? In some ways, a system call is just like a function call. The main difference is that the kernel code is invoked through a software interrupt or trap, which causes the code to execute in the kernel's context rather than the application's context. Apart from having a completely different memory layout, the kernel code runs with increased privileges (ring 0 on i386, supervisor mode on 680x0, etc). If you want to know the details, you'll need to read a reference book for the particular type of CPU. > When an application uses a library, the app and the library are > processed in DIFFERENT threads in which of the following cases: > > 1. the library is statically linked > 2. the library is dynamically linked > 3. the library is loaded using dlopen > > My guess is "none of the above", am I right? Correct. Many applications don't use threads at all. Even for those which do, any calls to a library function are executed in the same thread as the code which call it. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
