From: Thomas Monjalon <thomas.monjalon@6wind.com>
To: "François-Frédéric Ozog" <ff@ozog.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] Bit spinlocks in DPDK
Date: Fri, 20 Dec 2013 16:39:05 +0100 [thread overview]
Message-ID: <201312201639.05277.thomas.monjalon@6wind.com> (raw)
In-Reply-To: <01d001cef375$7167e300$5437a900$@com>
Hello,
07/12/2013 18:54, François-Frédéric Ozog :
> 1) If the critical section deals with weakly ordered loads then explicit
> fencing MUST be used: if not, out of order execution will just kill your
> idea of critical section.
[...]
> So use rte_mb() or rte_wmb() or rte_rmb() where appropriate. I recommend
> the rte_unlock code and documentation explains the out of order execution
> issues and the conditions they have to be mitigated with rte*mb(). I
> wonder if having an explicit mfence in rte_sinlock_unlock wouldn't be just
> necessary to avoid "hairy" bugs. In addition, we would have
> rte_sinlock_unlock_no_mb used internally for performance reasons, and
> usable externally by advanced users.
Using lock prefix is lighter than using memory barrier and have the same
effects.
But you're right about the bug in spinlocks.
I am going to send a patch for this.
--
Thomas
next prev parent reply other threads:[~2013-12-20 15:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-06 21:04 Pashupati Kumar
2013-12-06 22:02 ` Thomas Monjalon
2013-12-06 22:12 ` Pashupati Kumar
2013-12-06 22:24 ` Thomas Monjalon
2013-12-06 22:54 ` Pashupati Kumar
2013-12-07 17:54 ` François-Frédéric Ozog
2013-12-19 16:41 ` Thomas Monjalon
2013-12-20 15:39 ` Thomas Monjalon [this message]
2013-12-20 16:00 ` François-Frédéric Ozog
2013-12-20 16:36 ` Stephen Hemminger
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