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mirror of https://github.com/edk2-porting/linux-next.git synced 2025-01-23 04:54:01 +08:00
linux-next/net/rxrpc
David Howells 001c112249 rxrpc: Maintain an extra ref on a conn for the cache list
Overhaul the usage count accounting for the rxrpc_connection struct to make
it easier to implement RCU access from the data_ready handler.

The problem is that currently we're using a lock to prevent the garbage
collector from trying to clean up a connection that we're contemplating
unidling.  We could just stick incoming packets on the connection we find,
but we've then got a problem that we may race when dispatching a work item
to process it as we need to give that a ref to prevent the rxrpc_connection
struct from disappearing in the meantime.

Further, incoming packets may get discarded if attached to an
rxrpc_connection struct that is going away.  Whilst this is not a total
disaster - the client will presumably resend - it would delay processing of
the call.  This would affect the AFS client filesystem's service manager
operation.

To this end:

 (1) We now maintain an extra count on the connection usage count whilst it
     is on the connection list.  This mean it is not in use when its
     refcount is 1.

 (2) When trying to reuse an old connection, we only increment the refcount
     if it is greater than 0.  If it is 0, we replace it in the tree with a
     new candidate connection.

 (3) Two connection flags are added to indicate whether or not a connection
     is in the local's client connection tree (used by sendmsg) or the
     peer's service connection tree (used by data_ready).  This makes sure
     that we don't try and remove a connection if it got replaced.

     The flags are tested under lock with the removal operation to prevent
     the reaper from killing the rxrpc_connection struct whilst someone
     else is trying to effect a replacement.

     This could probably be alleviated by using memory barriers between the
     flag set/test and the rb_tree ops.  The rb_tree op would still need to
     be under the lock, however.

 (4) When trying to reap an old connection, we try to flip the usage count
     from 1 to 0.  If it's not 1 at that point, then it must've come back
     to life temporarily and we ignore it.

Signed-off-by: David Howells <dhowells@redhat.com>
2016-07-06 10:50:04 +01:00
..
af_rxrpc.c rxrpc: Add RCU destruction for connections and calls 2016-07-06 10:43:51 +01:00
ar-internal.h rxrpc: Maintain an extra ref on a conn for the cache list 2016-07-06 10:50:04 +01:00
call_accept.c rxrpc: Move peer lookup from call-accept to new-incoming-conn 2016-07-06 10:49:57 +01:00
call_event.c rxrpc: Access socket accept queue under right lock 2016-07-06 10:43:51 +01:00
call_object.c rxrpc: Call channels should have separate call number spaces 2016-07-06 10:43:52 +01:00
conn_client.c rxrpc: Maintain an extra ref on a conn for the cache list 2016-07-06 10:50:04 +01:00
conn_event.c rxrpc: Call channels should have separate call number spaces 2016-07-06 10:43:52 +01:00
conn_object.c rxrpc: Maintain an extra ref on a conn for the cache list 2016-07-06 10:50:04 +01:00
conn_service.c rxrpc: Maintain an extra ref on a conn for the cache list 2016-07-06 10:50:04 +01:00
input.c rxrpc: Move usage count getting into rxrpc_queue_conn() 2016-07-06 10:43:51 +01:00
insecure.c rxrpc: Avoid using stack memory in SG lists in rxkad 2016-07-06 10:43:05 +01:00
Kconfig rxrpc: Absorb the rxkad security module 2016-04-11 15:34:41 -04:00
key.c rxrpc: Use structs to hold connection params and protocol info 2016-06-22 09:09:59 +01:00
local_event.c rxrpc: Rework local endpoint management 2016-06-15 15:38:17 +01:00
local_object.c rxrpc: Add RCU destruction for connections and calls 2016-07-06 10:43:51 +01:00
Makefile rxrpc: Split service connection code out into its own file 2016-07-06 10:49:35 +01:00
misc.c rxrpc: Limit the listening backlog 2016-06-10 18:14:47 -07:00
output.c rxrpc: Kill off the rxrpc_transport struct 2016-06-22 14:00:23 +01:00
peer_event.c rxrpc: Use the peer record to distribute network errors 2016-06-15 10:15:16 +01:00
peer_object.c rxrpc: Kill off the rxrpc_transport struct 2016-06-22 14:00:23 +01:00
proc.c rxrpc: Call channels should have separate call number spaces 2016-07-06 10:43:52 +01:00
recvmsg.c rxrpc: Replace conn->trans->{local,peer} with conn->params.{local,peer} 2016-06-22 09:10:00 +01:00
rxkad.c rxrpc: Call channels should have separate call number spaces 2016-07-06 10:43:52 +01:00
security.c rxrpc: Replace conn->trans->{local,peer} with conn->params.{local,peer} 2016-06-22 09:10:00 +01:00
skbuff.c rxrpc: Rename files matching ar-*.c to git rid of the "ar-" prefix 2016-06-13 12:16:05 +01:00
sysctl.c rxrpc: Kill off the rxrpc_transport struct 2016-06-22 14:00:23 +01:00
utils.c rxrpc: Move peer lookup from call-accept to new-incoming-conn 2016-07-06 10:49:57 +01:00