diff options
| author | Andy Grover <andy.grover@oracle.com> | 2009-04-01 08:20:20 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-04-02 00:52:22 -0700 |
| commit | 8cbd9606a6367c221a7bbcc47f3ab1a8c31b6437 (patch) | |
| tree | 9ff2adf88be32383fd59dc133f1cd6670b9ee815 /net/rds/iw_recv.c | |
| parent | 745cbccac3fe8cead529a1b3358e1e86a1505bfa (diff) | |
RDS: Use spinlock to protect 64b value update on 32b archs
We have a 64bit value that needs to be set atomically.
This is easy and quick on all 64bit archs, and can also be done
on x86/32 with set_64bit() (uses cmpxchg8b). However other
32b archs don't have this.
I actually changed this to the current state in preparation for
mainline because the old way (using a spinlock on 32b) resulted in
unsightly #ifdefs in the code. But obviously, being correct takes
precedence.
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/iw_recv.c')
| -rw-r--r-- | net/rds/iw_recv.c | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/net/rds/iw_recv.c b/net/rds/iw_recv.c index a1931f0027a2..fde470fa50d5 100644 --- a/net/rds/iw_recv.c +++ b/net/rds/iw_recv.c @@ -395,10 +395,37 @@ void rds_iw_recv_init_ack(struct rds_iw_connection *ic) * room for it beyond the ring size. Send completion notices its special * wr_id and avoids working with the ring in that case. */ +#ifndef KERNEL_HAS_ATOMIC64 static void rds_iw_set_ack(struct rds_iw_connection *ic, u64 seq, int ack_required) { - rds_iw_set_64bit(&ic->i_ack_next, seq); + unsigned long flags; + + spin_lock_irqsave(&ic->i_ack_lock, flags); + ic->i_ack_next = seq; + if (ack_required) + set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags); + spin_unlock_irqrestore(&ic->i_ack_lock, flags); +} + +static u64 rds_iw_get_ack(struct rds_iw_connection *ic) +{ + unsigned long flags; + u64 seq; + + clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags); + + spin_lock_irqsave(&ic->i_ack_lock, flags); + seq = ic->i_ack_next; + spin_unlock_irqrestore(&ic->i_ack_lock, flags); + + return seq; +} +#else +static void rds_iw_set_ack(struct rds_iw_connection *ic, u64 seq, + int ack_required) +{ + atomic64_set(&ic->i_ack_next, seq); if (ack_required) { smp_mb__before_clear_bit(); set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags); @@ -410,8 +437,10 @@ static u64 rds_iw_get_ack(struct rds_iw_connection *ic) clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags); smp_mb__after_clear_bit(); - return ic->i_ack_next; + return atomic64_read(&ic->i_ack_next); } +#endif + static void rds_iw_send_ack(struct rds_iw_connection *ic, unsigned int adv_credits) { @@ -464,6 +493,10 @@ static void rds_iw_send_ack(struct rds_iw_connection *ic, unsigned int adv_credi * - i_ack_next, which is the last sequence number we received * * Potentially, send queue and receive queue handlers can run concurrently. + * It would be nice to not have to use a spinlock to synchronize things, + * but the one problem that rules this out is that 64bit updates are + * not atomic on all platforms. Things would be a lot simpler if + * we had atomic64 or maybe cmpxchg64 everywhere. * * Reconnecting complicates this picture just slightly. When we * reconnect, we may be seeing duplicate packets. The peer |