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Date: Tue, 17 Mar 2015 21:06:35 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com> Cc: Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Nicholas Miell <nmiell@...cast.net>, Linus Torvalds <torvalds@...ux-foundation.org>, Ingo Molnar <mingo@...hat.com>, Alan Cox <gnomes@...rguk.ukuu.org.uk>, Lai Jiangshan <laijs@...fujitsu.com>, Stephen Hemminger <stephen@...workplumber.org>, Andrew Morton <akpm@...ux-foundation.org>, Josh Triplett <josh@...htriplett.org>, Thomas Gleixner <tglx@...utronix.de>, David Howells <dhowells@...hat.com> Subject: Re: [RFC PATCH] sys_membarrier(): system/process-wide memory barrier (x86) (v12) On Tue, 17 Mar 2015 12:46:41 +0000 (UTC) Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote: > > Would that help? > > > > this_cpu_write(saved_next, next); > > rq = context_switch(rq, prev, next); > > rq->curr = this_cpu_read(saved_next); > > Assuming there is a full memory barrier (e.g. load_cr3) within > context_switch, it would help for ordering memory accesses that > are performed prior to the preemption, but not for memory accesses > to be performed immediately after return to userspace from preemption. Hmm, I was thinking that there was a spin_unlock(rq->lock) after that, but it appears that context_switch() does the unlock. If there was an spin_unlock() after this code, then it could work. There's always setting the rq->curr in the context_switch() call itself. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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