netdev - Re: [PATCH 17/21] RDS/IB: Receive datagrams via IB

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Date:	Thu, 29 Jan 2009 13:47:03 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Olaf Kirch <okir@...e.de>
Cc:	Andy Grover <andy.grover@...cle.com>, rds-devel@....oracle.com,
	general@...ts.openfabrics.org, netdev@...r.kernel.org
Subject: Re: [PATCH 17/21] RDS/IB: Receive datagrams via IB

 > > > This is racy.  You check if you're at the limit, do the allocation, and
 > > > then increment the atomic rds_ib_allocation count.  So many threads can
 > > > pass the atomic_read() test and then take you over the limit.  If you
 > > > want to make it safe then you could do atomic_inc_return() and check if
 > > > that took you over the limit.
 > >
 > > Woah, yup, thanks.
 > 
 > The refill code used to be single-threaded; and I think it still is. So
 > this can't race I think

So you don't need the atomic op at all?

 - R.
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