From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: dhowells@redhat.com
Cc: linux-kernel@vger.kernel.org
Subject: Confused by smp_read_barrier_depends() in rxrpc_rotate_tx_window()
Date: Fri, 30 May 2008 05:45:54 -0700 [thread overview]
Message-ID: <20080530124554.GA14312@linux.vnet.ibm.com> (raw)
Hello, Dave!
I confess to being confused by the smp_read_barrier_depends() in
rxrpc_rotate_tx_window(). It looks like it is ordering the prior
fetch of tail from call->acks_tail with the subsequent use of
tail as an index into the call->acks_window[] array, but then the
code does an assignment to call->acks_tail a few lines later.
If we hold a lock protecting call->acks_tail, why do we need the
smp_read_barrier_depends()? If we don't hold such a lock, why
is the assignment to call->acks_tail safe?
Help?
Thanx, Paul
next reply other threads:[~2008-05-30 12:46 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-30 12:45 Paul E. McKenney [this message]
2008-06-03 10:19 ` Confused by smp_read_barrier_depends() in rxrpc_rotate_tx_window() David Howells
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