RE: Processor descriptor

["Yagnavarahan" <yagnavarahan@xxxxxxxxx>]

To get information about the currently running task we use:

current_task_info()->task

this looks up the Structure thread_info from where another Structure task_info is looked up

Maybe I am knive, I dont understand the C syntax, is current_task_info() a function.  Please explain the syntax in detail.

Best
A.S.

Hi,

 

the function current_thread_info is given as follows in asm/thread_info.h

 

static inline struct thread_info *current_thread_info(void)
{
    struct thread_info *ti;
    __asm__("andl %%esp, %0; ":"=r" (ti) : "0" (~8191UL));
    return ti;
}

 

The important thing to note is that it is protptyped to return a struct thread_info * (a thread_info pointer).

 

In C when you say current_thread_info()->task, the current_thread_info() part of the _expression_ evaluates to what is returned when this function is called (in this case a thread_info pointer). You can then access the task field in this struct.

 

Thus

 

struct task_struct *task = current_thread_info()->task

 

is essentially equivalent to

 

struct thread_info *ti;

 

ti = current_thread_info();
struct task_struct *task = ti->task;

 

Hope this helps.
Yagnavarahan