[PATCH 4/12] iseries_veth: Remove a FIXME WRT deletion of the ack_timer

[Michael Ellerman <michael@xxxxxxxxxxxxxx>]

The iseries_veth driver has a timer which we use to send acks. When the
connection is reset or stopped we need to delete the timer.

Currently we only call del_timer() when resetting a connection, which means
the timer might run again while the connection is being re-setup. As it turns
out that's ok, because the flags the timer consults have been reset.

It's cleaner though to call del_timer_sync() once we've dropped the lock,
although the timer may still run between us dropping the lock and calling
del_timer_sync(), but as above that's ok.


---

 drivers/net/iseries_veth.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)

Index: veth-dev/drivers/net/iseries_veth.c
===================================================================
--- veth-dev.orig/drivers/net/iseries_veth.c
+++ veth-dev/drivers/net/iseries_veth.c
@@ -450,13 +450,15 @@ static void veth_statemachine(void *p)
        if (cnx->state & VETH_STATE_RESET) {
                int i;
 
-               del_timer(&cnx->ack_timer);
-
                if (cnx->state & VETH_STATE_OPEN)
                        HvCallEvent_closeLpEventPath(cnx->remote_lp,
                                                     HvLpEvent_Type_VirtualLan);
 
-               /* reset ack data */
+               /*
+                * Reset ack data. This prevents the ack_timer actually
+                * doing anything, even if it runs one more time when
+                * we drop the lock below.
+                */
                memset(&cnx->pending_acks, 0xff, sizeof (cnx->pending_acks));
                cnx->num_pending_acks = 0;
 
@@ -469,9 +471,16 @@ static void veth_statemachine(void *p)
                if (cnx->msgs)
                        for (i = 0; i < VETH_NUMBUFFERS; ++i)
                                veth_recycle_msg(cnx, cnx->msgs + i);
+
+               /* Drop the lock so we can do stuff that might sleep or
+                * take other locks. */
                spin_unlock_irq(&cnx->lock);
+
+               del_timer_sync(&cnx->ack_timer);
                veth_flush_pending(cnx);
+
                spin_lock_irq(&cnx->lock);
+
                if (cnx->state & VETH_STATE_RESET)
                        goto restart;
        }
@@ -658,12 +667,8 @@ static void veth_stop_connection(u8 rlp)
        veth_kick_statemachine(cnx);
        spin_unlock_irq(&cnx->lock);
 
+       /* Wait for the state machine to run. */
        flush_scheduled_work();
-
-       /* FIXME: not sure if this is necessary - will already have
-        * been deleted by the state machine, just want to make sure
-        * its not running any more */
-       del_timer_sync(&cnx->ack_timer);
 }
 
 static void veth_destroy_connection(u8 rlp)