On Mon, Apr 30, 2018 at 08:13:11PM +0530, Pritam Bankar wrote:

Hi,

My question is, do all the code of interrupt handler in system call gets executed in interrupt context?

No.

System calls generate software interrupts.

Some do, some do not. It all depends :)

So when I do open() syscall it we call do_sys_open() handler which will eventually call file system specific open function call.

Normal file open calls do not generate a hardware interrupt. Some might, but some might not. It all depends.

Will all this happen in interrupt context until I get open file descriptor in user land?

No, if disk I/O is needed, which requires interrupts, the system call process (your process) will sleep in the kernel until the needed I/O happens and is returned. That I/O can cause irq code to run, and if so, that's fine, it runs in its own context.

If not when does context change?

Often and frequently :) Sorry, it's a complex thing, all depending on the hardware, system, cache, and loads of other things. Try using ftrace or other function tracing tools to follow a call through the kernel to see how this all plays out. hope this helps, greg k-h