We need barriers to guarantee this pattern works as intended: [w] req->rc, 1 [r] req->status, 1 wmb rmb [w] req->status, 1 [r] req->rc
Where the wmb ensures that rc gets written before status, and the rmb ensures that if you observe status == 1, rc is the new value. Signed-off-by: Dominique Martinet <[email protected]> --- include/net/9p/client.h | 2 +- net/9p/client.c | 16 +++++++++++++++- net/9p/trans_fd.c | 15 ++++++--------- net/9p/trans_rdma.c | 3 +-- net/9p/trans_virtio.c | 3 +-- 5 files changed, 24 insertions(+), 15 deletions(-) diff --git a/include/net/9p/client.h b/include/net/9p/client.h index c38a005..115aeac 100644 --- a/include/net/9p/client.h +++ b/include/net/9p/client.h @@ -261,7 +261,7 @@ int p9_client_mkdir_dotl(struct p9_fid *fid, char *name, int mode, int p9_client_lock_dotl(struct p9_fid *fid, struct p9_flock *flock, u8 *status); int p9_client_getlock_dotl(struct p9_fid *fid, struct p9_getlock *fl); struct p9_req_t *p9_tag_lookup(struct p9_client *, u16); -void p9_client_cb(struct p9_client *c, struct p9_req_t *req); +void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status); int p9_parse_header(struct p9_fcall *, int32_t *, int8_t *, int16_t *, int); int p9stat_read(struct p9_client *, char *, int, struct p9_wstat *); diff --git a/net/9p/client.c b/net/9p/client.c index ee8fd6b..03431f0 100644 --- a/net/9p/client.c +++ b/net/9p/client.c @@ -415,9 +415,17 @@ static void p9_free_req(struct p9_client *c, struct p9_req_t *r) * req: request received * */ -void p9_client_cb(struct p9_client *c, struct p9_req_t *req) +void p9_client_cb(struct p9_client *c, struct p9_req_t *req, int status) { p9_debug(P9_DEBUG_MUX, " tag %d\n", req->tc->tag); + + /* + * This barrier is needed to make sure any change made to req before + * the other thread wakes up will indeed be seen by the waiting side. + */ + smp_wmb(); + req->status = status; + wake_up(req->wq); p9_debug(P9_DEBUG_MUX, "wakeup: %d\n", req->tc->tag); } @@ -751,6 +759,12 @@ again: err = wait_event_interruptible(*req->wq, req->status >= REQ_STATUS_RCVD); + /* + * Make sure our req is coherent with regard to updates in other + * threads - echoes to wmb() in the callback + */ + smp_rmb(); + if ((err == -ERESTARTSYS) && (c->status == Connected) && (type == P9_TFLUSH)) { sigpending = 1; diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c index 9321a77..74e6bbc 100644 --- a/net/9p/trans_fd.c +++ b/net/9p/trans_fd.c @@ -212,15 +212,9 @@ static void p9_conn_cancel(struct p9_conn *m, int err) m->err = err; list_for_each_entry_safe(req, rtmp, &m->req_list, req_list) { - req->status = REQ_STATUS_ERROR; - if (!req->t_err) - req->t_err = err; list_move(&req->req_list, &cancel_list); } list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) { - req->status = REQ_STATUS_ERROR; - if (!req->t_err) - req->t_err = err; list_move(&req->req_list, &cancel_list); } spin_unlock_irqrestore(&m->client->lock, flags); @@ -228,7 +222,9 @@ static void p9_conn_cancel(struct p9_conn *m, int err) list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) { p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req); list_del(&req->req_list); - p9_client_cb(m->client, req); + if (!req->t_err) + req->t_err = err; + p9_client_cb(m->client, req, REQ_STATUS_ERROR); } } @@ -302,6 +298,7 @@ static void p9_read_work(struct work_struct *work) { int n, err; struct p9_conn *m; + int status = REQ_STATUS_ERROR; m = container_of(work, struct p9_conn, rq); @@ -375,10 +372,10 @@ static void p9_read_work(struct work_struct *work) p9_debug(P9_DEBUG_TRANS, "got new packet\n"); spin_lock(&m->client->lock); if (m->req->status != REQ_STATUS_ERROR) - m->req->status = REQ_STATUS_RCVD; + status = REQ_STATUS_RCVD; list_del(&m->req->req_list); spin_unlock(&m->client->lock); - p9_client_cb(m->client, m->req); + p9_client_cb(m->client, m->req, status); m->rbuf = NULL; m->rpos = 0; m->rsize = 0; diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c index 8f68df5..f127ae5 100644 --- a/net/9p/trans_rdma.c +++ b/net/9p/trans_rdma.c @@ -305,8 +305,7 @@ handle_recv(struct p9_client *client, struct p9_trans_rdma *rdma, } req->rc = c->rc; - req->status = REQ_STATUS_RCVD; - p9_client_cb(client, req); + p9_client_cb(client, req, REQ_STATUS_RCVD); return; diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c index 9c5a1aa..81785b7b 100644 --- a/net/9p/trans_virtio.c +++ b/net/9p/trans_virtio.c @@ -164,8 +164,7 @@ static void req_done(struct virtqueue *vq) p9_debug(P9_DEBUG_TRANS, ": rc %p\n", rc); p9_debug(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag); req = p9_tag_lookup(chan->client, rc->tag); - req->status = REQ_STATUS_RCVD; - p9_client_cb(chan->client, req); + p9_client_cb(chan->client, req, REQ_STATUS_RCVD); } } -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
