Linux 3.16中的SPIN_LOCK_UNLOCKED等效于什么？

Question

Here is a line from a kernel module that I wrote for a 2.x kernel.

static spinlock_t mr_lock = SPIN_LOCK_UNLOCKED;

When I try to compile this module for a 3.16 kernel, I get the following build error.

error: ‘SPIN_LOCK_UNLOCKED’ undeclared here (not in a function)

When I look at the 3.16 version of linux/spinlock_types.h , which defines the spinlock_t type for this kernel, there is indeed no SPIN_LOCK_UNLOCKED constant anymore.

However, it is not clear how to initialize a spinlock to unlocked for this kernel.

What is the correct way to achieve the same initialization?

Answer 1

It depends on how you were using it.

#define DEFINE_SPINLOCK(x)    spinlock_t x = __SPIN_LOCK_UNLOCKED(x)

to replace code like:

  spinlock_t init_lock = SPIN_LOCK_UNLOCKED;

with the improved:

  DEFINE_SPINLOCK(init_lock);

I took the above from this

https://www.mail-archive.com/kernelnewbies@nl.linux.org/msg02836.html