Re: [PATCH] mutex: Introduce mutex_cpu_relax()

Peter Zijlstra
2010-10-14T15:55:50Z

On Thu, 2010-10-14 at 17:33 +0200, Gerald Schaefer wrote:
> From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>
> The spinning mutex implementation uses cpu_relax() in busy loops as a
> compiler barrier. Depending on the architecture, cpu_relax() may do more
> than needed in this specific mutex spin loops. On System z we also give
> up the time slice of the virtual cpu in cpu_relax(), which prevents
> effective spinning on the mutex.
>
> This patch replaces cpu_relax() in the spinning mutex code with a new
> function mutex_cpu_relax(), which can be defined by each architecture
> that selects HAVE_MUTEX_CPU_RELAX. The default is still cpu_relax(), so
> this patch should not affect other architectures than System z for now.

Sure.. I'll take it.