Re: [GIT PULL] adaptive spinning mutexes

Linus Torvalds
2009-01-15T18:16:53Z

On Thu, 15 Jan 2009, Ingo Molnar wrote:
>
> btw., i think spin-mutexes have a design advantage here: in a lot of code
> areas it's quite difficult to use spinlocks - cannot allocate memory,
> cannot call any code that can sporadically block (but does not _normally_
> block), etc.
>
> With mutexes those atomicity constraints go away - and the performance
> profile should now be quite close to that of spinlocks as well.

Umm. Except if you wrote the code nicely and used spinlocks, you wouldn't
hold the lock over all those unnecessary and complex operations.

IOW, if you do pre-allocation instead of holding a lock over the
allocation, you win. So yes, spin-mutexes makes it easier to write the
code, but it also makes it easier to just plain be lazy.

Linus