From: Oleg Nesterov <oleg@redhat.com>
To: Jason Baron <jbaron@akamai.com>, "David S. Miller" <davem@davemloft.net>
Cc: Herbert Xu <herbert.xu@redhat.com>,
Yauheni Kaliuta <yauheni.kaliuta@redhat.com>,
netdev@vger.kernel.org
Subject: wrong smp_mb__after_atomic() in tcp_check_space() ?
Date: Mon, 23 Jan 2017 15:30:25 +0100 [thread overview]
Message-ID: <20170123143025.GA31676@redhat.com> (raw)
Hello,
smp_mb__after_atomic() looks wrong and misleading, sock_reset_flag() does the
non-atomic __clear_bit() and thus it can not guarantee test_bit(SOCK_NOSPACE)
(non-atomic too) won't be reordered.
It was added by 3c7151275c0c9a "tcp: add memory barriers to write space paths"
and the patch looks correct in that we need the barriers in tcp_check_space()
and tcp_poll() in theory, so it seems tcp_check_space() needs smp_mb() ?
Oleg.
next reply other threads:[~2017-01-23 14:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-23 14:30 Oleg Nesterov [this message]
2017-01-23 16:56 ` wrong smp_mb__after_atomic() in tcp_check_space() ? Jason Baron
2017-01-23 17:18 ` Oleg Nesterov
2017-01-23 18:04 ` Eric Dumazet
2017-01-23 18:45 ` Jason Baron
2017-01-24 9:18 ` Oleg Nesterov
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