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Commit c081a0c7 authored by Greg Banks's avatar Greg Banks Committed by Linus Torvalds
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[PATCH] knfsd: test and set SK_BUSY atomically 



The SK_BUSY bit in svc_sock->sk_flags ensures that we do not attempt to
enqueue a socket twice.  Currently, setting and clearing the bit is protected
by svc_serv->sv_lock.  As I intend to reduce the data that the lock protects
so it's not held when svc_sock_enqueue() tests and sets SK_BUSY, that test and
set needs to be atomic.

Signed-off-by: default avatarGreg Banks <gnb@melbourne.sgi.com>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5685f0fa

net/sunrpc/svcsock.c

+10 −10
Original line number Diff line number Diff line
@@ -48,12 +48,11 @@ 
 *

 *	svc_serv->sv_lock protects most stuff for that service.

 *	svc_sock->sk_defer_lock protects the svc_sock->sk_deferred list

 *	svc_sock->sk_flags.SK_BUSY prevents a svc_sock being enqueued multiply.

 *

 *	Some flags can be set to certain values at any time

 *	providing that certain rules are followed:

 *

 *	SK_BUSY  can be set to 0 at any time.  

 *		svc_sock_enqueue must be called afterwards

 *	SK_CONN, SK_DATA, can be set or cleared at any time.

 *		after a set, svc_sock_enqueue must be called.	

 *		after a clear, the socket must be read/accepted
@@ -170,8 +169,13 @@ svc_sock_enqueue(struct svc_sock *svsk) 
		goto out_unlock;

	}



	if (test_bit(SK_BUSY, &svsk->sk_flags)) {

		/* Don't enqueue socket while daemon is receiving */

	/* Mark socket as busy. It will remain in this state until the

	 * server has processed all pending data and put the socket back

	 * on the idle list.  We update SK_BUSY atomically because

	 * it also guards against trying to enqueue the svc_sock twice.

	 */

	if (test_and_set_bit(SK_BUSY, &svsk->sk_flags)) {

		/* Don't enqueue socket while already enqueued */

		dprintk("svc: socket %p busy, not enqueued\n", svsk->sk_sk);

		goto out_unlock;

	}
@@ -185,15 +189,11 @@ svc_sock_enqueue(struct svc_sock *svsk) 
		dprintk("svc: socket %p  no space, %d*2 > %ld, not enqueued\n",

			svsk->sk_sk, atomic_read(&svsk->sk_reserved)+serv->sv_bufsz,

			svc_sock_wspace(svsk));

		clear_bit(SK_BUSY, &svsk->sk_flags);

		goto out_unlock;

	}

	clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);



	/* Mark socket as busy. It will remain in this state until the

	 * server has processed all pending data and put the socket back

	 * on the idle list.

	 */

	set_bit(SK_BUSY, &svsk->sk_flags);



	if (!list_empty(&serv->sv_threads)) {

		rqstp = list_entry(serv->sv_threads.next,