From: Neil Brown <neilb@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
nfs@lists.sourceforge.net, gnb@sgi.com
Subject: Re: [RFC,PATCH 14/35] svc: Change sk_inuse to a kref
Date: Mon, 8 Oct 2007 13:52:12 +1000 [thread overview]
Message-ID: <18185.43372.936660.630626@notabene.brown> (raw)
In-Reply-To: message from Christoph Hellwig on Wednesday October 3
On Wednesday October 3, hch@infradead.org wrote:
> On Wed, Oct 03, 2007 at 11:11:39AM -0400, J. Bruce Fields wrote:
> > OK, but why are they a complete pain in the ass, and which hard-to-avoid
> > races are you thinking of? Is that documented somewhere?
>
> They lack a primitive equivalent to atomic_dec_and_test which is required
> if you need the lock to prevent it going up from zero again. There have
> been various lkml threads on this.
I think you mean an equivalent to atomic_dec_and_lock.
I have noticed that too. However I don't think it means that krefs
should be a avoided.
Rather, I think it means that we need something slightly different
(lrefs?) that use atomic_dec_and_lock instead of atomic_dec_and_test,
and then some accessible documentation which explains the different
common usage patterns of reference counting, and when krefs are
correct, and when lrefs are correct.
I'm in favour of using krefs for sk_inuse. dec_and_lock isn't an
issue in this case.
NeilBrown
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next prev parent reply other threads:[~2007-10-08 3:52 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-01 19:14 [RFC,PATCH 00/35] SVC Transport Switch Tom Tucker
2007-10-01 19:27 ` [RFC,PATCH 01/35] svc: Add an svc transport class Tom Tucker
2007-10-01 19:27 ` [RFC,PATCH 02/35] svc: Make svc_sock the tcp/udp transport Tom Tucker
2007-10-01 19:27 ` [RFC, PATCH 03/35] svc: Change the svc_sock in the rqstp structure to a transport Tom Tucker
2007-10-01 19:27 ` [RFC, PATCH 04/35] svc: Add a max payload value to the transport Tom Tucker
2007-10-02 14:54 ` Chuck Lever
2007-10-02 16:28 ` Tom Tucker
2007-10-03 11:09 ` Greg Banks
2007-10-03 14:26 ` Tom Tucker
2007-10-03 15:18 ` Chuck Lever
2007-10-04 1:10 ` Greg Banks
2007-10-01 19:27 ` [RFC, PATCH 05/35] svc: Move sk_sendto and sk_recvfrom to svc_xprt_class Tom Tucker
2007-10-02 15:04 ` Chuck Lever
2007-10-02 16:29 ` Tom Tucker
2007-10-02 16:57 ` Chuck Lever
2007-10-02 18:24 ` Tom Tucker
2007-10-02 18:30 ` Tom Tucker
2007-10-02 18:47 ` Chuck Lever
2007-10-02 19:55 ` Tom Tucker
2007-10-02 20:29 ` Chuck Lever
2007-10-02 20:35 ` Tom Tucker
2007-10-02 20:38 ` Tom Tucker
2007-10-04 1:34 ` Greg Banks
2007-10-04 1:21 ` Greg Banks
2007-10-03 11:13 ` Greg Banks
2007-10-01 19:27 ` [RFC, PATCH 06/35] svc: Add transport specific xpo_release function Tom Tucker
2007-10-02 15:18 ` Chuck Lever
2007-10-02 16:35 ` Tom Tucker
2007-10-04 1:48 ` Greg Banks
2007-10-01 19:27 ` [RFC,PATCH 07/35] svc: Add per-transport delete functions Tom Tucker
2007-10-01 19:27 ` [RFC,PATCH 08/35] svc: Add xpo_prep_reply_hdr Tom Tucker
2007-10-01 19:27 ` [RFC, PATCH 09/35] svc: Add a transport function that checks for write space Tom Tucker
2007-10-01 19:27 ` [RFC, PATCH 10/35] svc: Move close processing to a single place Tom Tucker
2007-10-01 19:27 ` [RFC,PATCH 11/35] svc: Add xpo_accept transport function Tom Tucker
2007-10-02 15:33 ` Chuck Lever
2007-10-02 16:41 ` Tom Tucker
2007-10-02 17:07 ` Chuck Lever
2007-10-02 18:28 ` Tom Tucker
2007-10-02 18:49 ` Chuck Lever
2007-10-04 1:54 ` Greg Banks
2007-10-01 19:27 ` [RFC, PATCH 12/35] svc: Add a generic transport svc_create_xprt function Tom Tucker
2007-10-02 15:39 ` Chuck Lever
2007-10-03 20:01 ` Tom Tucker
2007-10-03 20:04 ` Tom Tucker
2007-10-04 2:30 ` Greg Banks
2007-10-04 15:18 ` Chuck Lever
2007-10-01 19:27 ` [RFC, PATCH 13/35] svc: Change services to use new svc_create_xprt service Tom Tucker
2007-10-02 15:44 ` Chuck Lever
2007-10-02 16:45 ` Tom Tucker
2007-10-03 15:25 ` Chuck Lever
2007-10-03 16:23 ` Tom Tucker
2007-10-04 2:35 ` Greg Banks
2007-10-04 14:27 ` Tom Tucker
2007-10-09 17:09 ` J. Bruce Fields
2007-10-09 18:32 ` Tom Tucker
2007-10-09 19:49 ` J. Bruce Fields
2007-10-09 20:19 ` J. Bruce Fields
2007-10-01 19:28 ` [RFC,PATCH 14/35] svc: Change sk_inuse to a kref Tom Tucker
2007-10-03 11:12 ` Christoph Hellwig
2007-10-03 14:39 ` Tom Tucker
2007-10-03 14:45 ` J. Bruce Fields
2007-10-03 14:52 ` Christoph Hellwig
2007-10-03 15:11 ` J. Bruce Fields
2007-10-03 15:15 ` Christoph Hellwig
2007-10-08 3:52 ` Neil Brown [this message]
2007-10-03 15:13 ` Chuck Lever
2007-10-03 15:34 ` J. Bruce Fields
2007-10-04 2:51 ` Greg Banks
2007-10-01 19:28 ` [RFC, PATCH 15/35] svc: Move sk_flags to the svc_xprt structure Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 16/35] svc: Move sk_server and sk_pool to svc_xprt Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 17/35] svc: Make close transport independent Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 18/35] svc: Move sk_reserved to svc_xprt Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 19/35] svc: Make the enqueue service transport neutral and export it Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 20/35] svc: Make svc_send transport neutral Tom Tucker
2007-10-02 16:15 ` Chuck Lever
2007-10-02 16:46 ` Tom Tucker
2007-10-02 16:54 ` Chuck Lever
2007-10-04 2:59 ` Greg Banks
2007-10-01 19:28 ` [RFC, PATCH 21/35] svc: Change svc_sock_received to svc_xprt_received and export it Tom Tucker
2007-10-02 16:18 ` Chuck Lever
2007-10-01 19:28 ` [RFC,PATCH 22/35] svc: Remove sk_lastrecv Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 23/35] svc: Move the authinfo cache to svc_xprt Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 24/35] svc: Make deferral processing xprt independent Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 25/35] svc: Move the sockaddr information to svc_xprt Tom Tucker
2007-10-02 16:34 ` Chuck Lever
2007-10-02 16:50 ` Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 26/35] svc: Make svc_sock_release svc_xprt_release Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 27/35] svc: Make svc_recv transport neutral Tom Tucker
2007-10-02 16:36 ` Chuck Lever
2007-10-01 19:28 ` [RFC, PATCH 28/35] svc: Make svc_age_temp_sockets svc_age_temp_transports Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 29/35] svc: Move common create logic to common code Tom Tucker
2007-10-02 16:42 ` Chuck Lever
2007-10-02 16:51 ` Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 30/35] svc: Removing remaining references to rq_sock in rqstp Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 31/35] svc: Make svc_check_conn_limits xprt independent Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 32/35] svc: Move the xprt independent code to the svc_xprt.c file Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 33/35] svc: Add transport hdr size for defer/revisit Tom Tucker
2007-10-01 19:28 ` [RFC,PATCH 34/35] svc: Add /proc/sys/sunrpc/transport files Tom Tucker
2007-10-01 19:28 ` [RFC, PATCH 35/35] knfsd: Support adding transports by writing portlist file Tom Tucker
2007-10-02 15:25 ` [RFC,PATCH 00/35] SVC Transport Switch J. Bruce Fields
2007-10-02 16:18 ` Tom Tucker
2007-10-03 11:03 ` Greg Banks
2007-10-03 14:02 ` Tom Tucker
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