Hi Sage,
Sage Weil wrote:
Hi Jim,
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?
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. 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).
So I've got logs now that show that connection state changes
across a call to process_message. That seems like it proves
the concept.
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.
Is there any reason not to fix all the cases at once, in try_read?
It's less code, but far away from where the mutex dropping occurs,
so we add a comment:
diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index a9bd424..11d6a61 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1816,10 +1820,19 @@ static int try_read(struct ceph_connection *con)
dout("try_read start on %p state %lu\n", con, con->state);
more:
dout("try_read %p state %lu tag %d in_base_pos %d\n", con,
con->state, (int)con->in_tag, con->in_base_pos);
+
+ /* process_connect, process_message need to drop con->mutex,
+ * so connection state might have changed on us. Check it,
+ * leave if necessary so new state can be processed.
+ */
+ if (test_bit(CLOSED, &con->state) ||
+ test_bit(OPENING, &con->state))
+ goto out;
+
if (test_bit(CONNECTING, &con->state)) {
if (!test_bit(NEGOTIATING, &con->state)) {
dout("try_read %p connecting\n", con);
ret = read_partial_banner(con);
if (ret <= 0)
What am I missing?
-- Jim
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