On Tue, Mar 17, 2015 at 06:30:35PM +0100, Peter Zijlstra wrote: > On Tue, Mar 17, 2015 at 01:22:02PM -0400, Mathieu Desnoyers wrote: > > Here is an implementation of a new system call, sys_membarrier(), which > > executes a memory barrier on either all running threads of the current > > process (MEMBARRIER_PRIVATE) issues a memory barrier on all threads > > running on the system (~MEMBARRIER_PRIVATE). Both are currently > > implemented by calling synchronize_sched(). > > Then why bother with the flag?
Semantically, MEMBARRIER_PRIVATE is allowed to avoid issuing a barrier on CPUs not running the current process if it can, while ~MEMBARRIER_PRIVATE may not. (The latter would be useful for applications such as system-wide tracing.) That they're currently both implemented the same way doesn't mean they're semantically equivalent. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
