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Jetpack/kernel/kernel-4.9/rt-patches/0239-net-Qdisc-use-a-seqloc...

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From aeb0f0d33b308849a15f2f26410bb8d786d11869 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 14 Sep 2016 17:36:35 +0200
Subject: [PATCH 239/352] net/Qdisc: use a seqlock instead seqcount
The seqcount disables preemption on -RT while it is held which can't
remove. Also we don't want the reader to spin for ages if the writer is
scheduled out. The seqlock on the other hand will serialize / sleep on
the lock while writer is active.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/seqlock.h | 9 +++++++++
include/net/gen_stats.h | 9 +++++----
include/net/net_seq_lock.h | 15 +++++++++++++++
include/net/sch_generic.h | 21 ++++++++++++++++++---
net/core/gen_estimator.c | 6 +++---
net/core/gen_stats.c | 8 ++++----
net/sched/sch_api.c | 2 +-
net/sched/sch_generic.c | 12 ++++++++++++
8 files changed, 67 insertions(+), 15 deletions(-)
create mode 100644 include/net/net_seq_lock.h
diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 17a8721..3d7223f 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -481,6 +481,15 @@ static inline void write_seqlock(seqlock_t *sl)
__raw_write_seqcount_begin(&sl->seqcount);
}
+static inline int try_write_seqlock(seqlock_t *sl)
+{
+ if (spin_trylock(&sl->lock)) {
+ __raw_write_seqcount_begin(&sl->seqcount);
+ return 1;
+ }
+ return 0;
+}
+
static inline void write_sequnlock(seqlock_t *sl)
{
__raw_write_seqcount_end(&sl->seqcount);
diff --git a/include/net/gen_stats.h b/include/net/gen_stats.h
index 231e121..d125222 100644
--- a/include/net/gen_stats.h
+++ b/include/net/gen_stats.h
@@ -5,6 +5,7 @@
#include <linux/socket.h>
#include <linux/rtnetlink.h>
#include <linux/pkt_sched.h>
+#include <net/net_seq_lock.h>
struct gnet_stats_basic_cpu {
struct gnet_stats_basic_packed bstats;
@@ -33,11 +34,11 @@ int gnet_stats_start_copy_compat(struct sk_buff *skb, int type,
spinlock_t *lock, struct gnet_dump *d,
int padattr);
-int gnet_stats_copy_basic(const seqcount_t *running,
+int gnet_stats_copy_basic(net_seqlock_t *running,
struct gnet_dump *d,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b);
-void __gnet_stats_copy_basic(const seqcount_t *running,
+void __gnet_stats_copy_basic(net_seqlock_t *running,
struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b);
@@ -55,14 +56,14 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
- seqcount_t *running, struct nlattr *opt);
+ net_seqlock_t *running, struct nlattr *opt);
void gen_kill_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_rate_est64 *rate_est);
int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
- seqcount_t *running, struct nlattr *opt);
+ net_seqlock_t *running, struct nlattr *opt);
bool gen_estimator_active(const struct gnet_stats_basic_packed *bstats,
const struct gnet_stats_rate_est64 *rate_est);
#endif
diff --git a/include/net/net_seq_lock.h b/include/net/net_seq_lock.h
new file mode 100644
index 0000000..a703429
--- /dev/null
+++ b/include/net/net_seq_lock.h
@@ -0,0 +1,15 @@
+#ifndef __NET_NET_SEQ_LOCK_H__
+#define __NET_NET_SEQ_LOCK_H__
+
+#ifdef CONFIG_PREEMPT_RT_BASE
+# define net_seqlock_t seqlock_t
+# define net_seq_begin(__r) read_seqbegin(__r)
+# define net_seq_retry(__r, __s) read_seqretry(__r, __s)
+
+#else
+# define net_seqlock_t seqcount_t
+# define net_seq_begin(__r) read_seqcount_begin(__r)
+# define net_seq_retry(__r, __s) read_seqcount_retry(__r, __s)
+#endif
+
+#endif
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 538f3c4..1f49824 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -10,6 +10,7 @@
#include <linux/dynamic_queue_limits.h>
#include <net/gen_stats.h>
#include <net/rtnetlink.h>
+#include <net/net_seq_lock.h>
struct Qdisc_ops;
struct qdisc_walker;
@@ -86,7 +87,7 @@ struct Qdisc {
struct sk_buff *gso_skb ____cacheline_aligned_in_smp;
struct qdisc_skb_head q;
struct gnet_stats_basic_packed bstats;
- seqcount_t running;
+ net_seqlock_t running;
struct gnet_stats_queue qstats;
unsigned long state;
struct Qdisc *next_sched;
@@ -98,13 +99,22 @@ struct Qdisc {
spinlock_t busylock ____cacheline_aligned_in_smp;
};
-static inline bool qdisc_is_running(const struct Qdisc *qdisc)
+static inline bool qdisc_is_running(struct Qdisc *qdisc)
{
+#ifdef CONFIG_PREEMPT_RT_BASE
+ return spin_is_locked(&qdisc->running.lock) ? true : false;
+#else
return (raw_read_seqcount(&qdisc->running) & 1) ? true : false;
+#endif
}
static inline bool qdisc_run_begin(struct Qdisc *qdisc)
{
+#ifdef CONFIG_PREEMPT_RT_BASE
+ if (try_write_seqlock(&qdisc->running))
+ return true;
+ return false;
+#else
if (qdisc_is_running(qdisc))
return false;
/* Variant of write_seqcount_begin() telling lockdep a trylock
@@ -113,11 +123,16 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
raw_write_seqcount_begin(&qdisc->running);
seqcount_acquire(&qdisc->running.dep_map, 0, 1, _RET_IP_);
return true;
+#endif
}
static inline void qdisc_run_end(struct Qdisc *qdisc)
{
+#ifdef CONFIG_PREEMPT_RT_BASE
+ write_sequnlock(&qdisc->running);
+#else
write_seqcount_end(&qdisc->running);
+#endif
}
static inline bool qdisc_may_bulk(const struct Qdisc *qdisc)
@@ -308,7 +323,7 @@ static inline spinlock_t *qdisc_root_sleeping_lock(const struct Qdisc *qdisc)
return qdisc_lock(root);
}
-static inline seqcount_t *qdisc_root_sleeping_running(const struct Qdisc *qdisc)
+static inline net_seqlock_t *qdisc_root_sleeping_running(const struct Qdisc *qdisc)
{
struct Qdisc *root = qdisc_root_sleeping(qdisc);
diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c
index cad8e79..2a9364f 100644
--- a/net/core/gen_estimator.c
+++ b/net/core/gen_estimator.c
@@ -84,7 +84,7 @@ struct gen_estimator
struct gnet_stats_basic_packed *bstats;
struct gnet_stats_rate_est64 *rate_est;
spinlock_t *stats_lock;
- seqcount_t *running;
+ net_seqlock_t *running;
int ewma_log;
u32 last_packets;
unsigned long avpps;
@@ -213,7 +213,7 @@ int gen_new_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
- seqcount_t *running,
+ net_seqlock_t *running,
struct nlattr *opt)
{
struct gen_estimator *est;
@@ -309,7 +309,7 @@ int gen_replace_estimator(struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu_bstats,
struct gnet_stats_rate_est64 *rate_est,
spinlock_t *stats_lock,
- seqcount_t *running, struct nlattr *opt)
+ net_seqlock_t *running, struct nlattr *opt)
{
gen_kill_estimator(bstats, rate_est);
return gen_new_estimator(bstats, cpu_bstats, rate_est, stats_lock, running, opt);
diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index 18f17e1..9afe5d6 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -142,7 +142,7 @@ __gnet_stats_copy_basic_cpu(struct gnet_stats_basic_packed *bstats,
}
void
-__gnet_stats_copy_basic(const seqcount_t *running,
+__gnet_stats_copy_basic(net_seqlock_t *running,
struct gnet_stats_basic_packed *bstats,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b)
@@ -155,10 +155,10 @@ __gnet_stats_copy_basic(const seqcount_t *running,
}
do {
if (running)
- seq = read_seqcount_begin(running);
+ seq = net_seq_begin(running);
bstats->bytes = b->bytes;
bstats->packets = b->packets;
- } while (running && read_seqcount_retry(running, seq));
+ } while (running && net_seq_retry(running, seq));
}
EXPORT_SYMBOL(__gnet_stats_copy_basic);
@@ -176,7 +176,7 @@ EXPORT_SYMBOL(__gnet_stats_copy_basic);
* if the room in the socket buffer was not sufficient.
*/
int
-gnet_stats_copy_basic(const seqcount_t *running,
+gnet_stats_copy_basic(net_seqlock_t *running,
struct gnet_dump *d,
struct gnet_stats_basic_cpu __percpu *cpu,
struct gnet_stats_basic_packed *b)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index ea13df1..76c2074 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -980,7 +980,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
rcu_assign_pointer(sch->stab, stab);
}
if (tca[TCA_RATE]) {
- seqcount_t *running;
+ net_seqlock_t *running;
err = -EOPNOTSUPP;
if (sch->flags & TCQ_F_MQROOT)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 2cff9e4..77d50f2 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -425,7 +425,11 @@ struct Qdisc noop_qdisc = {
.ops = &noop_qdisc_ops,
.q.lock = __SPIN_LOCK_UNLOCKED(noop_qdisc.q.lock),
.dev_queue = &noop_netdev_queue,
+#ifdef CONFIG_PREEMPT_RT_BASE
+ .running = __SEQLOCK_UNLOCKED(noop_qdisc.running),
+#else
.running = SEQCNT_ZERO(noop_qdisc.running),
+#endif
.busylock = __SPIN_LOCK_UNLOCKED(noop_qdisc.busylock),
};
EXPORT_SYMBOL(noop_qdisc);
@@ -624,9 +628,17 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
lockdep_set_class(&sch->busylock,
dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
+#ifdef CONFIG_PREEMPT_RT_BASE
+ seqlock_init(&sch->running);
+ lockdep_set_class(&sch->running.seqcount,
+ dev->qdisc_running_key ?: &qdisc_running_key);
+ lockdep_set_class(&sch->running.lock,
+ dev->qdisc_running_key ?: &qdisc_running_key);
+#else
seqcount_init(&sch->running);
lockdep_set_class(&sch->running,
dev->qdisc_running_key ?: &qdisc_running_key);
+#endif
sch->ops = ops;
sch->enqueue = ops->enqueue;
--
2.7.4
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