Date: Tue, 17 Jul 2012 21:15:50 +0200
Subject: setup_thread_stack
From: francesco.sc...@gmail.com
To: kernelnewbies@kernelnewbies.org
Hi,
I'm totally new to kernel code, just trying to understand the basics of the
core subsystems.
During the do_fork call, there is a call to dup_task_struct, which in turn
calls setup_thread_stack.
What's this call supposed to do? Inside I can see a call to the
"task_thread_info" macro, but I don't quite understand it:
#define task_thread_info(task) ((struct thread_info *)(task)->stack)
can a task_struct be cast to a thread_info? perhaps my C knowledge should be
improved..I know :(
Sorry for the trivial question..just trying to understand :)
it is nothing about C, but architecture of kernel. kernel put thread_info of
every process at the bottom of stack.
please reference thread_info.h for your specific cpu architecture:
/*
* how to get the thread information struct from C
*/
static inline struct thread_info *current_thread_info(void) __attribute_const__;
static inline struct thread_info *current_thread_info(void)
{
register unsigned long sp asm ("sp");
return (struct thread_info *)(sp & ~(THREAD_SIZE - 1));
}
because kernel put thread_info at the bottom of stack, so when one process is
running, kernel can use above inline
function to get the thread_info conveniently.
Regards,
Francesco
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