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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>
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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14
net/rds/ib.h
View File

@ -108,7 +108,12 @@ struct rds_ib_connection {
/* sending acks */
unsigned long i_ack_flags;
#ifdef KERNEL_HAS_ATOMIC64
atomic64_t i_ack_next; /* next ACK to send */
#else
spinlock_t i_ack_lock; /* protect i_ack_next */
u64 i_ack_next; /* next ACK to send */
#endif
struct rds_header *i_ack;
struct ib_send_wr i_ack_wr;
struct ib_sge i_ack_sge;
@ -363,13 +368,4 @@ rds_ib_data_sge(struct rds_ib_connection *ic, struct ib_sge *sge)
return &sge[1];
}
static inline void rds_ib_set_64bit(u64 *ptr, u64 val)
{
#if BITS_PER_LONG == 64
*ptr = val;
#else
set_64bit(ptr, val);
#endif
}
#endif

9
net/rds/ib_cm.c
View File

@ -636,7 +636,11 @@ void rds_ib_conn_shutdown(struct rds_connection *conn)
/* Clear the ACK state */
clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
rds_ib_set_64bit(&ic->i_ack_next, 0);
#ifdef KERNEL_HAS_ATOMIC64
atomic64_set(&ic->i_ack_next, 0);
#else
ic->i_ack_next = 0;
#endif
ic->i_ack_recv = 0;
/* Clear flow control state */
@ -669,6 +673,9 @@ int rds_ib_conn_alloc(struct rds_connection *conn, gfp_t gfp)
INIT_LIST_HEAD(&ic->ib_node);
mutex_init(&ic->i_recv_mutex);
#ifndef KERNEL_HAS_ATOMIC64
spin_lock_init(&ic->i_ack_lock);
#endif
/*
* rds_ib_conn_shutdown() waits for these to be emptied so they

37
net/rds/ib_recv.c
View File

@ -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

14
net/rds/iw.h
View File

@ -131,7 +131,12 @@ struct rds_iw_connection {
/* sending acks */
unsigned long i_ack_flags;
#ifdef KERNEL_HAS_ATOMIC64
atomic64_t i_ack_next; /* next ACK to send */
#else
spinlock_t i_ack_lock; /* protect i_ack_next */
u64 i_ack_next; /* next ACK to send */
#endif
struct rds_header *i_ack;
struct ib_send_wr i_ack_wr;
struct ib_sge i_ack_sge;
@ -391,13 +396,4 @@ rds_iw_data_sge(struct rds_iw_connection *ic, struct ib_sge *sge)
return &sge[1];
}
static inline void rds_iw_set_64bit(u64 *ptr, u64 val)
{
#if BITS_PER_LONG == 64
*ptr = val;
#else
set_64bit(ptr, val);
#endif
}
#endif

9
net/rds/iw_cm.c
View File

@ -659,7 +659,11 @@ void rds_iw_conn_shutdown(struct rds_connection *conn)
/* Clear the ACK state */
clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
rds_iw_set_64bit(&ic->i_ack_next, 0);
#ifdef KERNEL_HAS_ATOMIC64
atomic64_set(&ic->i_ack_next, 0);
#else
ic->i_ack_next = 0;
#endif
ic->i_ack_recv = 0;
/* Clear flow control state */
@ -693,6 +697,9 @@ int rds_iw_conn_alloc(struct rds_connection *conn, gfp_t gfp)
INIT_LIST_HEAD(&ic->iw_node);
mutex_init(&ic->i_recv_mutex);
#ifndef KERNEL_HAS_ATOMIC64
spin_lock_init(&ic->i_ack_lock);
#endif
/*
* rds_iw_conn_shutdown() waits for these to be emptied so they

37
net/rds/iw_recv.c
View File

@ -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

4
net/rds/rds.h
View File

@ -28,6 +28,10 @@
*/
#define RDS_PORT 18634
#ifdef ATOMIC64_INIT
#define KERNEL_HAS_ATOMIC64
#endif
#ifdef DEBUG
#define rdsdebug(fmt, args...) pr_debug("%s(): " fmt, __func__ , ##args)
#else