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RDS: Use spinlock to protect 64b value update on 32b archs

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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>
This commit is contained in:
Andy Grover
2009-04-01 08:20:20 +00:00
committed by David S. Miller
parent 745cbccac3
commit 8cbd9606a6
7 changed files with 100 additions and 24 deletions
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37
net/rds/ib_recv.c
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@@ -395,10 +395,37 @@ void rds_ib_recv_init_ack(struct rds_ib_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_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
int ack_required)
{
rds_ib_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_ib_get_ack(struct rds_ib_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_ib_set_ack(struct rds_ib_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_ib_get_ack(struct rds_ib_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_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
{
@@ -464,6 +493,10 @@ static void rds_ib_send_ack(struct rds_ib_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