| Message ID | Pine.LNX.4.64.1105161033150.12367@cobra.newdream.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Sage, Sage Weil wrote: > Hi Jim, > > Finally had some time to look at this closely. This is great work > nailing down the misbehavior. Here's what confuses me: > > - con_work takes con->mutex and does (almost) everything under the > protection of that lock. > - con_close and con_open both take it as well when they twiddle with state > - therefore, after the close/open are called by __reset_osd(), the next > call into con_work should see the OPENING bit is set. > > Of course, it doesn't. See below... > >> [ 2392.366919] libceph: tid 447 timed out on osd20, will reset osd >> [ 2392.366922] libceph: osd_client.c:725 : __reset_osd ffff8801955c0000 osd20 >> [ 2392.366926] libceph: messenger.c:349 : con_close ffff8801955c0030 peer 172.17.40.27:6800 >> >>>> A message times out, __reset_osd signals that connection should be closed; work >>>> queued to connection is discarded. >> [ 2392.366934] libceph: messenger.c:369 : con_open ffff8801955c0030 172.17.40.27:6800 >> >>>> __reset_osd signals that connection should be opened. >> [ 2392.367237] libceph: messenger.c:2159 : ----- ffff88018f91c600 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367242] libceph: messenger.c:2159 : ----- ffff88018f91d6c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367247] libceph: messenger.c:2159 : ----- ffff88018f920a80 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367251] libceph: messenger.c:2159 : ----- ffff88018f924d80 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367256] libceph: messenger.c:2159 : ----- ffff88018f926480 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367260] libceph: messenger.c:2159 : ----- ffff88018f92f240 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367265] libceph: messenger.c:2159 : ----- ffff88018f930d80 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367269] libceph: messenger.c:2159 : ----- ffff88018be14f00 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367274] libceph: messenger.c:2159 : ----- ffff88018be1b3c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367279] libceph: messenger.c:2159 : ----- ffff88018be210c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367283] libceph: messenger.c:2159 : ----- ffff88018d9c69c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367288] libceph: messenger.c:2159 : ----- ffff88018d85f9c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367293] libceph: messenger.c:2159 : ----- ffff88018daf2300 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367297] libceph: messenger.c:2159 : ----- ffff88018f8b6600 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367302] libceph: messenger.c:2159 : ----- ffff88018be28840 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367307] libceph: messenger.c:2159 : ----- ffff880154105240 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367311] libceph: messenger.c:2159 : ----- ffff88015410a300 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367316] libceph: messenger.c:2159 : ----- ffff88015410f0c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367320] libceph: messenger.c:2159 : ----- ffff880154116d80 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367325] libceph: messenger.c:2159 : ----- ffff8801541176c0 to osd20 42=osd_op len 128+0+524288 ----- >> [ 2392.367329] libceph: messenger.c:2159 : ----- ffff88015411bb40 to osd20 42=osd_op len 128+0+524288 ----- >> >>>> Outstanding work is requeued to connection. >> [ 2397.376206] libceph: messenger.c:2230 : con_keepalive ffff8801955c0030 >> [ 2402.384140] libceph: messenger.c:2230 : con_keepalive ffff8801955c0030 >> [ 2407.395283] libceph: messenger.c:2230 : con_keepalive ffff8801955c0030 >> [ 2411.207412] libceph: messenger.c:2177 : con_revoke ffff8801955c0030 msg ffff88018f91c600 - was on queue > > Not sure why the first message was revoked... but that shouldn't matter... > >> [ 2411.217092] libceph: messenger.c:1708 : try_write start ffff8801955c0030 state 8220 nref 1 >> [ 2411.225536] libceph: messenger.c:1712 : try_write ffff8801955c0030 out_msg (null) out_kvec_bytes 0 >> [ 2411.235555] libceph: messenger.c:509 : prepare_write_message ffff8801955c0030 msg ffff88018f91d6c0 seq 1 type 42 len 128+0+524288 128 pgs >> [ 2411.256874] libceph: messenger.c:1712 : try_write ffff8801955c0030 out_msg ffff88018f91d6c0 out_kvec_bytes 191 >> [ 2411.267280] libceph: messenger.c:1790 : try_write done on ffff8801955c0030 ret 0 > > This picks up the second resent message. But and OPENING is set.. so how > is it that we were in try_write but we didn't pass through the OPENING > test in con_work? The only way I see this could happen is if this instance of con_work passed through that test before OPENING was set. That's what made me think "race". But, look at the time stamps. 18.85 seconds pass between con_open and try_write !! I don't see how that could happen unless the instance of con_work that called try_write above was stuck in try_read for most of that 18.85 seconds. I'll check that out. Also, AFAICS neither ceph_con_open nor ceph_con_close take con->mutex while they are twiddling bits in con->state. But here's a fun fact I didn't mention earlier since it didn't help: putting everything in both ceph_con_open and ceph_con_close except the call to queue_con(con) under con->mutex didn't help at all. So it must be something else. > >>>> con_work()/try_write() start again on new message. >>>> Note that con_work() did not notice that the connection was marked to >>>> be closed/reopened! This is where things went bad. >>>> Note the connection state: 8220 = 0x201c, and 0x2000 is OPENING. >> [ 2412.643178] libceph: messenger.c:1969 : con_work ffff8801955c0030 OPENING >> [ 2412.643182] libceph: messenger.c:292 : con_close_socket on ffff8801955c0030 sock ffff8801825a8c00 >> [ 2412.643197] libceph: messenger.c:162 : ceph_state_change ffff8801955c0030 state = 2076 sk_state = 4 > > Ok, now we see it, but this should have executed before we ever got to > try_write! > > There are a handful of places that drop and re-take con->mutex... I think > it has to be one of those. OK, I will look at them. They are: > > - prepare_connect_authorizer (before calling ->prepare_authorizer > callback) > - fail_protocol (before calling ->bad_proto callback) > - process_connect RESETSESSION case (before calling ->reset callback) > - process_message (before calling ->dispatch callback) > > I think after retaking the lock in each of these cases we need to test for > the CLOSED or OPENING bits and, if set, bail out so that con_work can > restart. > > Does that make sense? Can you confirm which case of lock droppage inside > con_work is at fault? (Maybe adding a printk at the top of con_work after > taking the lock too would make it more clear what's going on; currently it > only prints in all the random test_bit cases). > > I'm thinking something like the below... does that seem reasonable? I > only did the prepare_authorizer case to start, but the others should be > fixed up too. Compile tested only. OK, I'll fix them all up and let you know what I learn. > > BTW, I looked at the second patch too. Messages should only be requeued > for non-lossy connections, and that's done in ceph_fault by the > list_splice call. The current out_msg is placed on the out_sent list when > we first start, so it is already included in that set. I don't think any > special casing is needed there. OK, thanks; there's lots of details I haven't fully understood yet. -- Jim > > Thanks for hunting this down! > sage > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index e15a82c..544d52c 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -598,7 +598,7 @@ static void prepare_write_keepalive(struct ceph_connection *con) * Connection negotiation. */ -static void prepare_connect_authorizer(struct ceph_connection *con) +static int prepare_connect_authorizer(struct ceph_connection *con) { void *auth_buf; int auth_len = 0; @@ -612,6 +612,10 @@ static void prepare_connect_authorizer(struct ceph_connection *con) con->auth_retry); mutex_lock(&con->mutex); + if (test_bit(CLOSED, &con->state) || + test_bit(OPENING, &con->state)) + return -EAGAIN; + con->out_connect.authorizer_protocol = cpu_to_le32(auth_protocol); con->out_connect.authorizer_len = cpu_to_le32(auth_len); @@ -619,6 +623,7 @@ static void prepare_connect_authorizer(struct ceph_connection *con) con->out_kvec[con->out_kvec_left].iov_len = auth_len; con->out_kvec_left++; con->out_kvec_bytes += auth_len; + return 0; } /* @@ -640,9 +645,9 @@ static void prepare_write_banner(struct ceph_messenger *msgr, set_bit(WRITE_PENDING, &con->state); } -static void prepare_write_connect(struct ceph_messenger *msgr, - struct ceph_connection *con, - int after_banner) +static int prepare_write_connect(struct ceph_messenger *msgr, + struct ceph_connection *con, + int after_banner) { unsigned global_seq = get_global_seq(con->msgr, 0); int proto; @@ -683,7 +688,7 @@ static void prepare_write_connect(struct ceph_messenger *msgr, con->out_more = 0; set_bit(WRITE_PENDING, &con->state); - prepare_connect_authorizer(con); + return prepare_connect_authorizer(con); } @@ -1216,6 +1221,7 @@ static int process_connect(struct ceph_connection *con) u64 sup_feat = con->msgr->supported_features; u64 req_feat = con->msgr->required_features; u64 server_feat = le64_to_cpu(con->in_reply.features); + int r; dout("process_connect on %p tag %d\n", con, (int)con->in_tag); @@ -1250,7 +1256,9 @@ static int process_connect(struct ceph_connection *con) return -1; } con->auth_retry = 1; - prepare_write_connect(con->msgr, con, 0); + r = prepare_write_connect(con->msgr, con, 0); + if (r < 0) + return r; prepare_read_connect(con); break; @@ -1938,6 +1946,7 @@ static void con_work(struct work_struct *work) { struct ceph_connection *con = container_of(work, struct ceph_connection, work.work); + int ret; mutex_lock(&con->mutex); if (test_and_clear_bit(BACKOFF, &con->state)) { @@ -1958,6 +1967,7 @@ static void con_work(struct work_struct *work) dout("con_work %p STANDBY\n", con); goto done; } +restart: if (test_bit(CLOSED, &con->state)) { /* e.g. if we are replaced */ dout("con_work CLOSED\n"); con_close_socket(con); @@ -1969,18 +1979,32 @@ static void con_work(struct work_struct *work) con_close_socket(con); } - if (test_and_clear_bit(SOCK_CLOSED, &con->state) || - try_read(con) < 0 || - try_write(con) < 0) { - mutex_unlock(&con->mutex); - ceph_fault(con); /* error/fault path */ - goto done_unlocked; - } + if (test_and_clear_bit(SOCK_CLOSED, &con->state)) + goto fault; + + ret = try_read(con); + if (ret == -EAGAIN) + goto restart; + if (ret < 0) + goto fault; + + ret = try_write(con); + if (ret == -EAGAIN) + goto restart; + if (ret < 0) + goto fault; done: mutex_unlock(&con->mutex); done_unlocked: con->ops->put(con); + return; + + +fault: + mutex_unlock(&con->mutex); + ceph_fault(con); + goto done_unlocked; }