----- Original Message ----- > From: "Josh Triplett" <[email protected]> > To: "Mathieu Desnoyers" <[email protected]> > Cc: [email protected], "KOSAKI Motohiro" > <[email protected]>, "Steven Rostedt" > <[email protected]>, "Paul E. McKenney" <[email protected]>, > "Nicholas Miell" <[email protected]>, > "Linus Torvalds" <[email protected]>, "Ingo Molnar" > <[email protected]>, "Alan Cox" > <[email protected]>, "Lai Jiangshan" <[email protected]>, > "Stephen Hemminger" > <[email protected]>, "Andrew Morton" <[email protected]>, > "Thomas Gleixner" <[email protected]>, > "Peter Zijlstra" <[email protected]>, "David Howells" > <[email protected]>, "Nick Piggin" <[email protected]> > Sent: Sunday, March 15, 2015 11:25:50 PM > Subject: Re: [RFC PATCH] sys_membarrier(): system/process-wide memory barrier > (x86) (v12) > > On Sun, Mar 15, 2015 at 03:24:19PM -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_FLAG) or calls synchronize_sched() to issue > > a memory barrier on all threads running on the system. It can be used to > > distribute the cost of user-space memory barriers asymmetrically by > > transforming pairs of memory barriers into pairs consisting of > > sys_membarrier() and a compiler barrier. For synchronization primitives > > that distinguish between read-side and write-side (e.g. userspace RCU, > > rwlocks), the read-side can be accelerated significantly by moving the > > bulk of the memory barrier overhead to the write-side. > > From a quick review, this seems quite reasonable (as it did 5 years > ago). > > One request: Could you please add a config option (default y) in the > EXPERT menu to disable this? You actually seem to already have it > marked as a cond_syscall.
Sure, done. > > Also, a very minor nit: flags in kernel APIs aren't typically named with > a _FLAG suffix. OK, good point. > > With the syscall made optional, and with or without that naming nit > fixed: > Reviewed-by: Josh Triplett <[email protected]> Thanks! Mathieu > > - Josh Triplett > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
