sunrpc: remove xpt_pool
The xpt_pool field is only used for reporting BUGs. And it isn't used correctly. In particular, when it is cleared in svc_xprt_received before XPT_BUSY is cleared, there is no guarantee that either the compiler or the CPU might not re-order to two assignments, just setting xpt_pool to NULL after XPT_BUSY is cleared. If a different cpu were running svc_xprt_enqueue at this moment, it might see XPT_BUSY clear and then xpt_pool non-NULL, and so BUG. This could be fixed by calling smp_mb__before_clear_bit() before the clear_bit. However as xpt_pool isn't really used, it seems safest to simply remove xpt_pool. Another alternate would be to change the clear_bit to clear_bit_unlock, and the test_and_set_bit to test_and_set_bit_lock. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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@ -63,7 +63,6 @@ struct svc_xprt {
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#define XPT_LISTENER 11 /* listening endpoint */
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#define XPT_LISTENER 11 /* listening endpoint */
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#define XPT_CACHE_AUTH 12 /* cache auth info */
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#define XPT_CACHE_AUTH 12 /* cache auth info */
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struct svc_pool *xpt_pool; /* current pool iff queued */
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struct svc_serv *xpt_server; /* service for transport */
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struct svc_serv *xpt_server; /* service for transport */
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atomic_t xpt_reserved; /* space on outq that is rsvd */
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atomic_t xpt_reserved; /* space on outq that is rsvd */
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struct mutex xpt_mutex; /* to serialize sending data */
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struct mutex xpt_mutex; /* to serialize sending data */
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@ -351,8 +351,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
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dprintk("svc: transport %p busy, not enqueued\n", xprt);
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dprintk("svc: transport %p busy, not enqueued\n", xprt);
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goto out_unlock;
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goto out_unlock;
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}
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}
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BUG_ON(xprt->xpt_pool != NULL);
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xprt->xpt_pool = pool;
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if (!list_empty(&pool->sp_threads)) {
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if (!list_empty(&pool->sp_threads)) {
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rqstp = list_entry(pool->sp_threads.next,
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rqstp = list_entry(pool->sp_threads.next,
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@ -370,13 +368,11 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
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rqstp->rq_reserved = serv->sv_max_mesg;
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rqstp->rq_reserved = serv->sv_max_mesg;
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atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
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atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
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pool->sp_stats.threads_woken++;
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pool->sp_stats.threads_woken++;
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BUG_ON(xprt->xpt_pool != pool);
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wake_up(&rqstp->rq_wait);
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wake_up(&rqstp->rq_wait);
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} else {
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} else {
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dprintk("svc: transport %p put into queue\n", xprt);
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dprintk("svc: transport %p put into queue\n", xprt);
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list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
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list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
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pool->sp_stats.sockets_queued++;
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pool->sp_stats.sockets_queued++;
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BUG_ON(xprt->xpt_pool != pool);
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}
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}
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out_unlock:
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out_unlock:
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@ -415,7 +411,6 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
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void svc_xprt_received(struct svc_xprt *xprt)
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void svc_xprt_received(struct svc_xprt *xprt)
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{
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{
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BUG_ON(!test_bit(XPT_BUSY, &xprt->xpt_flags));
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BUG_ON(!test_bit(XPT_BUSY, &xprt->xpt_flags));
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xprt->xpt_pool = NULL;
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/* As soon as we clear busy, the xprt could be closed and
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/* As soon as we clear busy, the xprt could be closed and
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* 'put', so we need a reference to call svc_xprt_enqueue with:
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* 'put', so we need a reference to call svc_xprt_enqueue with:
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*/
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*/
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