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Date: Wed, 1 Apr 2009 11:20:20 -0700
From: Andy Grover <andy.grover@...cle.com>
To: netdev@...r.kernel.org
Cc: rds-devel@....oracle.com
Subject: [PATCH 3/3] 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@...cle.com>
---
net/rds/ib.h | 14 +++++---------
net/rds/ib_cm.c | 9 ++++++++-
net/rds/ib_recv.c | 37 +++++++++++++++++++++++++++++++++++--
net/rds/iw.h | 14 +++++---------
net/rds/iw_cm.c | 9 ++++++++-
net/rds/iw_recv.c | 37 +++++++++++++++++++++++++++++++++++--
net/rds/rds.h | 4 ++++
7 files changed, 100 insertions(+), 24 deletions(-)
diff --git a/net/rds/ib.h b/net/rds/ib.h
index c08ffff..069206c 100644
--- a/net/rds/ib.h
+++ b/net/rds/ib.h
@@ -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
diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 889ab04..f8e40e1 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -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
diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 5061b55..36d9315 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -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
diff --git a/net/rds/iw.h b/net/rds/iw.h
index 70eb948..b4fb272 100644
--- a/net/rds/iw.h
+++ b/net/rds/iw.h
@@ -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
diff --git a/net/rds/iw_cm.c b/net/rds/iw_cm.c
index 0ffaa3e..a416b0d 100644
--- a/net/rds/iw_cm.c
+++ b/net/rds/iw_cm.c
@@ -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
diff --git a/net/rds/iw_recv.c b/net/rds/iw_recv.c
index a1931f0..fde470f 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
diff --git a/net/rds/rds.h b/net/rds/rds.h
index 0604007..619f0a3 100644
--- a/net/rds/rds.h
+++ b/net/rds/rds.h
@@ -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
--
1.5.6.3
--
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