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rxrpc: Fix error distribution

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Fix error distribution by immediately delivering the errors to all the
affected calls rather than deferring them to a worker thread.  The problem
with the latter is that retries and things can happen in the meantime when we
want to stop that sooner.

To this end:

 (1) Stop the error distributor from removing calls from the error_targets
     list so that peer->lock isn't needed to synchronise against other adds
     and removals.

 (2) Require the peer's error_targets list to be accessed with RCU, thereby
     avoiding the need to take peer->lock over distribution.

 (3) Don't attempt to affect a call's state if it is already marked complete.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells
2018-09-27 15:13:09 +01:00
parent 37a675e768
commit f334430316
7 changed files with 16 additions and 64 deletions
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46
net/rxrpc/peer_event.c
View File

@@ -23,6 +23,8 @@
#include "ar-internal.h"
static void rxrpc_store_error(struct rxrpc_peer *, struct sock_exterr_skb *);
static void rxrpc_distribute_error(struct rxrpc_peer *, int,
enum rxrpc_call_completion);
/*
* Find the peer associated with an ICMP packet.
@@ -194,8 +196,6 @@ void rxrpc_error_report(struct sock *sk)
rcu_read_unlock();
rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
/* The ref we obtained is passed off to the work item */
__rxrpc_queue_peer_error(peer);
_leave("");
}
@@ -205,6 +205,7 @@ void rxrpc_error_report(struct sock *sk)
static void rxrpc_store_error(struct rxrpc_peer *peer,
struct sock_exterr_skb *serr)
{
enum rxrpc_call_completion compl = RXRPC_CALL_NETWORK_ERROR;
struct sock_extended_err *ee;
int err;
@@ -255,7 +256,7 @@ static void rxrpc_store_error(struct rxrpc_peer *peer,
case SO_EE_ORIGIN_NONE:
case SO_EE_ORIGIN_LOCAL:
_proto("Rx Received local error { error=%d }", err);
err += RXRPC_LOCAL_ERROR_OFFSET;
compl = RXRPC_CALL_LOCAL_ERROR;
break;
case SO_EE_ORIGIN_ICMP6:
@@ -264,48 +265,23 @@ static void rxrpc_store_error(struct rxrpc_peer *peer,
break;
}
peer->error_report = err;
rxrpc_distribute_error(peer, err, compl);
}
/*
* Distribute an error that occurred on a peer
* Distribute an error that occurred on a peer.
*/
void rxrpc_peer_error_distributor(struct work_struct *work)
static void rxrpc_distribute_error(struct rxrpc_peer *peer, int error,
enum rxrpc_call_completion compl)
{
struct rxrpc_peer *peer =
container_of(work, struct rxrpc_peer, error_distributor);
struct rxrpc_call *call;
enum rxrpc_call_completion compl;
int error;
_enter("");
error = READ_ONCE(peer->error_report);
if (error < RXRPC_LOCAL_ERROR_OFFSET) {
compl = RXRPC_CALL_NETWORK_ERROR;
} else {
compl = RXRPC_CALL_LOCAL_ERROR;
error -= RXRPC_LOCAL_ERROR_OFFSET;
}
_debug("ISSUE ERROR %s %d", rxrpc_call_completions[compl], error);
spin_lock_bh(&peer->lock);
while (!hlist_empty(&peer->error_targets)) {
call = hlist_entry(peer->error_targets.first,
struct rxrpc_call, error_link);
hlist_del_init(&call->error_link);
hlist_for_each_entry_rcu(call, &peer->error_targets, error_link) {
rxrpc_see_call(call);
if (rxrpc_set_call_completion(call, compl, 0, -error))
if (call->state < RXRPC_CALL_COMPLETE &&
rxrpc_set_call_completion(call, compl, 0, -error))
rxrpc_notify_socket(call);
}
spin_unlock_bh(&peer->lock);
rxrpc_put_peer(peer);
_leave("");
}
/*