On Fri, Nov 21, 2014 at 02:19:28PM -0500, Jeff Layton wrote:
> ...also make the manipulation of sp_all_threads list use RCU-friendly
> functions.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
> Tested-by: Chris Worley <chris.worley@xxxxxxxxxxxxxxx>
> ---
> include/linux/sunrpc/svc.h | 2 ++
> include/trace/events/sunrpc.h | 3 ++-
> net/sunrpc/svc.c | 10 ++++++----
> 3 files changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
> index 5f0ab39bf7c3..7f80a99c59e4 100644
> --- a/include/linux/sunrpc/svc.h
> +++ b/include/linux/sunrpc/svc.h
> @@ -223,6 +223,7 @@ static inline void svc_putu32(struct kvec *iov, __be32 val)
> struct svc_rqst {
> struct list_head rq_list; /* idle list */
> struct list_head rq_all; /* all threads list */
> + struct rcu_head rq_rcu_head; /* for RCU deferred kfree */
> struct svc_xprt * rq_xprt; /* transport ptr */
>
> struct sockaddr_storage rq_addr; /* peer address */
> @@ -262,6 +263,7 @@ struct svc_rqst {
> #define RQ_SPLICE_OK (4) /* turned off in gss privacy
> * to prevent encrypting page
> * cache pages */
> +#define RQ_VICTIM (5) /* about to be shut down */
> unsigned long rq_flags; /* flags field */
>
> void * rq_argp; /* decoded arguments */
> diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
> index 5848fc235869..08a5fed50f34 100644
> --- a/include/trace/events/sunrpc.h
> +++ b/include/trace/events/sunrpc.h
> @@ -418,7 +418,8 @@ TRACE_EVENT(xs_tcp_data_recv,
> { (1UL << RQ_LOCAL), "RQ_LOCAL"}, \
> { (1UL << RQ_USEDEFERRAL), "RQ_USEDEFERRAL"}, \
> { (1UL << RQ_DROPME), "RQ_DROPME"}, \
> - { (1UL << RQ_SPLICE_OK), "RQ_SPLICE_OK"})
> + { (1UL << RQ_SPLICE_OK), "RQ_SPLICE_OK"}, \
> + { (1UL << RQ_VICTIM), "RQ_VICTIM"})
>
> TRACE_EVENT(svc_recv,
> TP_PROTO(struct svc_rqst *rqst, int status),
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index 5d9a443d21f6..4edef32f3b9f 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -616,7 +616,7 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
> serv->sv_nrthreads++;
> spin_lock_bh(&pool->sp_lock);
> pool->sp_nrthreads++;
> - list_add(&rqstp->rq_all, &pool->sp_all_threads);
> + list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads);
> spin_unlock_bh(&pool->sp_lock);
> rqstp->rq_server = serv;
> rqstp->rq_pool = pool;
> @@ -684,7 +684,8 @@ found_pool:
> * so we don't try to kill it again.
> */
> rqstp = list_entry(pool->sp_all_threads.next, struct svc_rqst, rq_all);
> - list_del_init(&rqstp->rq_all);
> + set_bit(RQ_VICTIM, &rqstp->rq_flags);
> + list_del_rcu(&rqstp->rq_all);
> task = rqstp->rq_task;
> }
> spin_unlock_bh(&pool->sp_lock);
> @@ -782,10 +783,11 @@ svc_exit_thread(struct svc_rqst *rqstp)
>
> spin_lock_bh(&pool->sp_lock);
> pool->sp_nrthreads--;
> - list_del(&rqstp->rq_all);
> + if (!test_and_set_bit(RQ_VICTIM, &rqstp->rq_flags))
> + list_del_rcu(&rqstp->rq_all);
Both users of RQ_VICTIM are under the sp_lock, so we don't really need
an atomic test_and_set_bit, do we?
But I guess svc_exit_thread probably still needs to check for the case
where it's called on a thread that svc_set_num_threads has already
chosen, and this works even if it's overkill. OK, fine.
--b.
> spin_unlock_bh(&pool->sp_lock);
>
> - kfree(rqstp);
> + kfree_rcu(rqstp, rq_rcu_head);
>
> /* Release the server */
> if (serv)
> --
> 2.1.0
>
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