Messages in this thread | | | Date | Sat, 29 Jun 2013 17:34:09 -0400 | From | Waiman Long <> | Subject | Re: [PATCH v2 1/2] spinlock: New spinlock_refcount.h for lockless update of refcount |
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On 06/29/2013 04:23 PM, Waiman Long wrote: > On 06/29/2013 01:45 PM, Linus Torvalds wrote: > >> But more importantly, I think this needs to be architecture-specific, >> and using<linux/spinlock_refcount.h> to try to do some generic 64-bit >> cmpxchg() version is a bad bad idea. > > Yes, I can put the current implementation into > asm-generic/spinlock_refcount.h. Now I need to put an > asm/spinlock_refcount.h into every arch's include/asm directory. > Right? I don't think there is a mechanism in the build script to > create a symlink from asm to generic-asm when a header file is > missing. Is it the general rule that we should have a > linux/spinlock_refcount.h that include asm/spinlock_refcount.h instead > of including asm/spinlock_refcount.h directly? > >> We have several architectures coming up that have memory transaction >> support, and the "spinlock with refcount" is a perfect candidate for a >> transactional memory implementation. So when introducing a new atomic >> like this that is very performance-critical and used for some very >> core code, I really think architectures would want to make their own >> optimized versions. >> >> These things should also not be inlined, I think. >>
I think I got it now. For architecture with transactional memory support to use an alternative implementation, we will need to use some kind of dynamic patching at kernel boot up time as not all CPUs in that architecture will have that support. In that case the helper functions have to be real functions and cannot be inlined. That means I need to put the implementation into a spinlock_refcount.c file with the header file contains structure definitions and function prototypes only. Is that what you are looking for?
Regards, Longman
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