Re: sem_lock() vs qspinlocks

[Peter Zijlstra]

On Sun, May 22, 2016 at 10:43:08AM +0200, Manfred Spraul wrote:
> How would we handle mixed spin_lock()/mutex_lock() code?
> For the IPC code, I would like to replace the outer lock with a mutex.
> The code only uses spinlocks, because at the time it was written, the mutex
> code didn't contain a busy wait.
> With a mutex, the code would become simpler (all the
> lock/unlock/kmalloc/relock parts could be removed).
> 
> The result would be something like:
> 
> 	mutex_lock(A)			spin_lock(B)
> 	spin_unlock_wait(B)		if (!mutex_is_locked(A))
> 	do_something()			  do_something()
> 

Should work similarly, but we'll have to audit mutex for these same
issues. I'll put it on todo.