atomic.h vs spinlock.h

atomic.h vs spinlock.h

[Umut Aymakoglu]

Hi -
   2 questions actually:

1) what is the difference between the macros defined in asm/atomic.h and
asm/spinlock.h. (usage and purpose wise)?

2) If I need to use asm/atomic.h, which macro can I use to test-and-set?


thanks,
Umut

Re: atomic.h vs spinlock.h

[David Mosberger]

>>>>> On Fri, 20 Jun 2003 16:00:45 -0700, Umut Aymakoglu <umuta@us.ibm.com> said:

  Umut> 1) what is the difference between the macros defined in
  Umut> asm/atomic.h and asm/spinlock.h. (usage and purpose wise)?

The first provides atomic operations, such as increment and decrement;
the second provides spinlocks.  I'm afraid I'm just stating the
obvious here.

In case you have a copy of my book (ia64 linux kernel), atomic ops and
spinlocks are described in sections 3.3.2 and 3.3.5, respectively.
(Of course, I wouldn't recommend to get the book _just_ because of
this.)

  Umut> 2) If I need to use asm/atomic.h, which macro can I use to
  Umut> test-and-set?

cmpxchg() is the closest thing to test-and-set.  Not all platforms support it.
Platforms that do support it (such as ia64), define macro __HAVE_ARCH_CMPXCHG.

	--david