[Question] I doublt on spin_lock again.

[liyu <liyu@ccoss.com.cn>]

Hi, All.

    I come here again.

    I have two questions on spin_lock. these are:

    1. I found these use spin_lock(&rq->lock) in set_user_nice(), but 
not disable interrput ( e.g.  when sys_nice() call it ),  if the one 
timer interrput come before we unlock the spin_lock, Shall
we dead lock here?  Since the scheduler_tick() may try to hold the same 
lock.

    2. I also found some function name in its definition have some 
postfix, I show here two classical examples:

static void double_rq_lock(runqueue_t *rq1, runqueue_t *rq2)
    __acquires(rq1->lock)
    __acquires(rq2->lock)
{ ... }

static void double_rq_unlock(runqueue_t *rq1, runqueue_t *rq2)
    __releases(rq1->lock)
    __releases(rq2->lock)
{ ... }

    In the related header files, they are defined as two preprocess 
macroes, are follow:

# define __acquires(x)    __attribute__((context(0,1)))
# define __releases(x)    __attribute__((context(1,0)))
# define __acquire(x)    __context__(1)
# define __release(x)    __context__(-1)


    I guess they are some extensions of gcc for C language, but I did 
not  found any information in GCC manual.

    Would you like reply these questions? Thank advanced.

-liyu