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Date:   Mon, 3 Jun 2019 12:01:14 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Fengguang Wu <fengguang.wu@intel.com>, LKP <lkp@01.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: rcu_read_lock lost its compiler barrier
Message-ID: <20190603040114.st646bujtgyu7adn@gondor.apana.org.au>
References: <20150910005708.GA23369@wfg-t540p.sh.intel.com>
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 <20150911021933.GA1521@fixme-laptop.cn.ibm.com>
 <20150921193045.GA13674@lerouge>
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On Sun, Jun 02, 2019 at 08:47:07PM -0700, Paul E. McKenney wrote:
>
> 	CPU2:         if (b != 1)
> 	CPU2:                 b = 1;

Stop right there.  The kernel is full of code that assumes that
assignment to an int/long is atomic.  If your compiler breaks this
assumption that we can kiss the kernel good-bye.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt