RE: [PATCH 3/3] IB/sa: route SA pathrecord query through netlink

From: "Hefty, Sean" <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: "Weiny, Ira" <ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Jason Gunthorpe
	<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: Or Gerlitz <gerlitz.or-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"Wan, Kaike" <kaike.wan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Or Gerlitz <ogerlitz-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	"linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"Fleck,
	John" <john.fleck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: RE: [PATCH 3/3] IB/sa: route SA pathrecord query through netlink
Date: Wed, 20 May 2015 16:13:59 +0000	[thread overview]
Message-ID: <1828884A29C6694DAF28B7E6B8A82373A8FDD971@ORSMSX109.amr.corp.intel.com> (raw)
In-Reply-To: <20150520090505.GA19896-W4f6Xiosr+yv7QzWx2u06xL4W9x8LtSr@public.gmane.org>

> The other issue is that each caller in the kernel specifies a different
> timeout.  Defining this in 1 central place and allowing user space to
> control
> the policy of that timeout is much better than allowing the kernel clients
> to
> specify the timeout as they do now.

Everything has been randomly hard-coded.  IMO, the sa_query module should use its own timeout value, which it updates based on how fast it actually gets responses.  But that takes too much work, and no one is ever going to write the code to do this.

For the netlink specific problem, I'll propose using a different randomly hard-coded value as a timeout.  Then define an 'MRA' type of message that user space can send to the kernel in order to ask it to wait longer.  The 'set timeout' message could apply to a single request or all future requests.  If we only wanted to the 'all future requests' option, the data value could be written into a file.  In any case, this pushes the policy of the timeout value into the hands of the responding daemon.

- Sean
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