From: Davidlohr Bueso <dave@stgolabs.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Manfred Spraul <manfred@colorfullife.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Susanne Spraul <1vier1@web.de>,
parri.andrea@gmail.com
Subject: Re: spin_lock implicit/explicit memory barrier
Date: Thu, 11 Aug 2016 11:31:06 -0700 [thread overview]
Message-ID: <20160811183106.GA18261@linux-80c1.suse> (raw)
In-Reply-To: <20160811081139.GT30192@twins.programming.kicks-ass.net>
On Thu, 11 Aug 2016, Peter Zijlstra wrote:
>On Wed, Aug 10, 2016 at 04:29:22PM -0700, Davidlohr Bueso wrote:
>
>> (1) As Manfred suggested, have a patch 1 that fixes the race against mainline
>> with the redundant smp_rmb, then apply a second patch that gets rid of it
>> for mainline, but only backport the original patch 1 down to 3.12.
>
>I have not followed the thread closely, but this seems like the best
>option. Esp. since 726328d92a42 ("locking/spinlock, arch: Update and fix
>spin_unlock_wait() implementations") is incomplete, it relies on at
>least 6262db7c088b ("powerpc/spinlock: Fix spin_unlock_wait()") to sort
>PPC.
Yeah, and we'd also need the arm bits; which reminds me, aren't alpha
ldl_l/stl_c sequences also exposed to this delaying of the publishing
when a non-owner peeks at the lock? Right now sysv sem's would be busted
when doing either is_locked or unlock_wait, shouldn't these be pimped up
to full smp_mb()s?
Thanks,
Davidlohr
next prev parent reply other threads:[~2016-08-11 18:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-09 18:52 spin_lock implicit/explicit memory barrier Manfred Spraul
2016-08-10 0:05 ` Benjamin Herrenschmidt
2016-08-10 18:21 ` Manfred Spraul
2016-08-10 19:17 ` Davidlohr Bueso
2016-08-10 21:00 ` Paul E. McKenney
2016-08-15 20:06 ` Manfred Spraul
2016-08-15 20:28 ` Paul E. McKenney
2016-08-12 2:47 ` Boqun Feng
2016-08-12 18:43 ` Manfred Spraul
2016-08-22 9:15 ` Boqun Feng
2016-08-10 20:52 ` Paul E. McKenney
2016-08-10 22:23 ` Davidlohr Bueso
2016-08-10 22:58 ` Paul E. McKenney
2016-08-10 23:29 ` Davidlohr Bueso
2016-08-11 8:11 ` Peter Zijlstra
2016-08-11 18:31 ` Davidlohr Bueso [this message]
2016-08-12 2:59 ` Boqun Feng
2016-08-19 14:01 ` Peter Zijlstra
2016-08-10 23:59 ` Benjamin Herrenschmidt
2016-08-10 18:33 ` Paul E. McKenney
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