[PATCH 17/41] net: Replace __this_cpu_inc in route.c with raw_cpu_inc

[PATCH 17/41] net: Replace __this_cpu_inc in route.c with raw_cpu_inc

[Christoph Lameter]

[-- Attachment #1: preempt_rt_cache_stat --]
[-- Type: text/plain, Size: 3614 bytes --]

[Patch depends on another patch in this series that introduces raw_cpu_ops]

The RT_CACHE_STAT_INC macro triggers the new preemption checks
for __this_cpu ops.

I do not see any other synchronization that would allow the use
of a __this_cpu operation here however in commit
dbd2915ce87e811165da0717f8e159276ebb803e Andrew justifies
the use of raw_smp_processor_id() here because "we do not care"
about races. In the past we agreed that the price of disabling
interrupts here to get consistent counters would be too high.
These counters may be inaccurate due to race conditions.

The use of __this_cpu op improves the situation already from what commit
dbd2915ce87e811165da0717f8e159276ebb803e did since the single instruction
emitted on x86 does not allow the race to occur anymore. However,
non x86 platforms could still experience a race here.

Trace:

[ 1277.189084] __this_cpu_add operation in preemptible [00000000] code: avahi-daemon/1193
[ 1277.189085] caller is __this_cpu_preempt_check+0x38/0x60
[ 1277.189086] CPU: 1 PID: 1193 Comm: avahi-daemon Tainted: GF            3.12.0-rc4+ #187
[ 1277.189087] Hardware name: FUJITSU CELSIUS W530 Power/D3227-A1, BIOS V4.6.5.4 R1.10.0 for D3227-A1x 09/16/2013
[ 1277.189088]  0000000000000001 ffff8807ef78fa00 ffffffff816d5a57 ffff8807ef78ffd8
[ 1277.189089]  ffff8807ef78fa30 ffffffff8137359c ffff8807ef78fba0 ffff88079f822b40
[ 1277.189091]  0000000020000000 ffff8807ee32c800 ffff8807ef78fa70 ffffffff813735f8
[ 1277.189093] Call Trace:
[ 1277.189094]  [<ffffffff816d5a57>] dump_stack+0x4e/0x82
[ 1277.189096]  [<ffffffff8137359c>] check_preemption_disabled+0xec/0x110
[ 1277.189097]  [<ffffffff813735f8>] __this_cpu_preempt_check+0x38/0x60
[ 1277.189098]  [<ffffffff81610d65>] __ip_route_output_key+0x575/0x8c0
[ 1277.189100]  [<ffffffff816110d7>] ip_route_output_flow+0x27/0x70
[ 1277.189101]  [<ffffffff81616c80>] ? ip_copy_metadata+0x1a0/0x1a0
[ 1277.189102]  [<ffffffff81640b15>] udp_sendmsg+0x825/0xa20
[ 1277.189104]  [<ffffffff811b4aa9>] ? do_sys_poll+0x449/0x5d0
[ 1277.189105]  [<ffffffff8164c695>] inet_sendmsg+0x85/0xc0
[ 1277.189106]  [<ffffffff815c6e3c>] sock_sendmsg+0x9c/0xd0
[ 1277.189108]  [<ffffffff813735f8>] ? __this_cpu_preempt_check+0x38/0x60
[ 1277.189109]  [<ffffffff815c7550>] ? move_addr_to_kernel+0x40/0xa0
[ 1277.189111]  [<ffffffff815c71ec>] ___sys_sendmsg+0x37c/0x390
[ 1277.189112]  [<ffffffff8136613a>] ? string.isra.3+0x3a/0xd0
[ 1277.189113]  [<ffffffff8136613a>] ? string.isra.3+0x3a/0xd0
[ 1277.189115]  [<ffffffff81367b54>] ? vsnprintf+0x364/0x650
[ 1277.189116]  [<ffffffff81367ee9>] ? snprintf+0x39/0x40
[ 1277.189118]  [<ffffffff813735f8>] ? __this_cpu_preempt_check+0x38/0x60
[ 1277.189119]  [<ffffffff815c7ff9>] __sys_sendmsg+0x49/0x90
[ 1277.189121]  [<ffffffff815c8052>] SyS_sendmsg+0x12/0x20
[ 1277.189122]  [<ffffffff816e4fd3>] tracesys+0xe1/0xe6

Cc: netdev@vger.kernel.org
Cc: davem@davemloft.net
Cc: edumazet@google.com
Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/net/ipv4/route.c
===================================================================
--- linux.orig/net/ipv4/route.c	2013-12-02 16:07:51.964573250 -0600
+++ linux/net/ipv4/route.c	2013-12-02 16:07:51.954573526 -0600
@@ -197,7 +197,7 @@ const __u8 ip_tos2prio[16] = {
 EXPORT_SYMBOL(ip_tos2prio);
 
 static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
-#define RT_CACHE_STAT_INC(field) __this_cpu_inc(rt_cache_stat.field)
+#define RT_CACHE_STAT_INC(field) raw_cpu_inc(rt_cache_stat.field)
 
 #ifdef CONFIG_PROC_FS
 static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)

[PATCH 24/41] net: Replace get_cpu_var through this_cpu_ptr

[Christoph Lameter]

[-- Attachment #1: this_net --]
[-- Type: text/plain, Size: 8883 bytes --]

[Patch depends on another patch in this series that introduces raw_cpu_ops]

Replace uses of get_cpu_var for address calculation through this_cpu_ptr.

Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/net/core/dev.c
===================================================================
--- linux.orig/net/core/dev.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/core/dev.c	2013-12-02 16:07:45.254759699 -0600
@@ -2130,7 +2130,7 @@ static inline void __netif_reschedule(st
 	unsigned long flags;
 
 	local_irq_save(flags);
-	sd = &__get_cpu_var(softnet_data);
+	sd = this_cpu_ptr(&softnet_data);
 	q->next_sched = NULL;
 	*sd->output_queue_tailp = q;
 	sd->output_queue_tailp = &q->next_sched;
@@ -2152,7 +2152,7 @@ void dev_kfree_skb_irq(struct sk_buff *s
 		unsigned long flags;
 
 		local_irq_save(flags);
-		sd = &__get_cpu_var(softnet_data);
+		sd = this_cpu_ptr(&softnet_data);
 		skb->next = sd->completion_queue;
 		sd->completion_queue = skb;
 		raise_softirq_irqoff(NET_TX_SOFTIRQ);
@@ -3122,7 +3122,7 @@ static void rps_trigger_softirq(void *da
 static int rps_ipi_queued(struct softnet_data *sd)
 {
 #ifdef CONFIG_RPS
-	struct softnet_data *mysd = &__get_cpu_var(softnet_data);
+	struct softnet_data *mysd = this_cpu_ptr(&softnet_data);
 
 	if (sd != mysd) {
 		sd->rps_ipi_next = mysd->rps_ipi_list;
@@ -3149,7 +3149,7 @@ static bool skb_flow_limit(struct sk_buf
 	if (qlen < (netdev_max_backlog >> 1))
 		return false;
 
-	sd = &__get_cpu_var(softnet_data);
+	sd = this_cpu_ptr(&softnet_data);
 
 	rcu_read_lock();
 	fl = rcu_dereference(sd->flow_limit);
@@ -3291,7 +3291,7 @@ EXPORT_SYMBOL(netif_rx_ni);
 
 static void net_tx_action(struct softirq_action *h)
 {
-	struct softnet_data *sd = &__get_cpu_var(softnet_data);
+	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 
 	if (sd->completion_queue) {
 		struct sk_buff *clist;
@@ -3711,7 +3711,7 @@ EXPORT_SYMBOL(netif_receive_skb);
 static void flush_backlog(void *arg)
 {
 	struct net_device *dev = arg;
-	struct softnet_data *sd = &__get_cpu_var(softnet_data);
+	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 	struct sk_buff *skb, *tmp;
 
 	rps_lock(sd);
@@ -4157,7 +4157,7 @@ void __napi_schedule(struct napi_struct
 	unsigned long flags;
 
 	local_irq_save(flags);
-	____napi_schedule(&__get_cpu_var(softnet_data), n);
+	____napi_schedule(this_cpu_ptr(&softnet_data), n);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL(__napi_schedule);
@@ -4285,7 +4285,7 @@ EXPORT_SYMBOL(netif_napi_del);
 
 static void net_rx_action(struct softirq_action *h)
 {
-	struct softnet_data *sd = &__get_cpu_var(softnet_data);
+	struct softnet_data *sd = this_cpu_ptr(&softnet_data);
 	unsigned long time_limit = jiffies + 2;
 	int budget = netdev_budget;
 	void *have;
Index: linux/net/core/drop_monitor.c
===================================================================
--- linux.orig/net/core/drop_monitor.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/core/drop_monitor.c	2013-12-02 16:07:45.254759699 -0600
@@ -147,7 +147,7 @@ static void trace_drop_common(struct sk_
 	unsigned long flags;
 
 	local_irq_save(flags);
-	data = &__get_cpu_var(dm_cpu_data);
+	data = this_cpu_ptr(&dm_cpu_data);
 	spin_lock(&data->lock);
 	dskb = data->skb;
 
Index: linux/net/core/skbuff.c
===================================================================
--- linux.orig/net/core/skbuff.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/core/skbuff.c	2013-12-02 16:07:45.254759699 -0600
@@ -371,7 +371,7 @@ static void *__netdev_alloc_frag(unsigne
 	unsigned long flags;
 
 	local_irq_save(flags);
-	nc = &__get_cpu_var(netdev_alloc_cache);
+	nc = this_cpu_ptr(&netdev_alloc_cache);
 	if (unlikely(!nc->frag.page)) {
 refill:
 		for (order = NETDEV_FRAG_PAGE_MAX_ORDER; ;) {
Index: linux/net/ipv4/tcp_output.c
===================================================================
--- linux.orig/net/ipv4/tcp_output.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/ipv4/tcp_output.c	2013-12-02 16:07:45.254759699 -0600
@@ -815,7 +815,7 @@ void tcp_wfree(struct sk_buff *skb)
 
 		/* queue this socket to tasklet queue */
 		local_irq_save(flags);
-		tsq = &__get_cpu_var(tsq_tasklet);
+		tsq = this_cpu_ptr(&tsq_tasklet);
 		list_add(&tp->tsq_node, &tsq->head);
 		tasklet_schedule(&tsq->tasklet);
 		local_irq_restore(flags);
Index: linux/net/ipv6/syncookies.c
===================================================================
--- linux.orig/net/ipv6/syncookies.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/ipv6/syncookies.c	2013-12-02 16:07:45.254759699 -0600
@@ -67,7 +67,7 @@ static u32 cookie_hash(const struct in6_
 
 	net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
 
-	tmp  = __get_cpu_var(ipv6_cookie_scratch);
+	tmp  = this_cpu_ptr(ipv6_cookie_scratch);
 
 	/*
 	 * we have 320 bits of information to hash, copy in the remaining
Index: linux/net/rds/ib_rdma.c
===================================================================
--- linux.orig/net/rds/ib_rdma.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/rds/ib_rdma.c	2013-12-02 16:07:45.254759699 -0600
@@ -267,7 +267,7 @@ static inline struct rds_ib_mr *rds_ib_r
 	unsigned long *flag;
 
 	preempt_disable();
-	flag = &__get_cpu_var(clean_list_grace);
+	flag = this_cpu_ptr(&clean_list_grace);
 	set_bit(CLEAN_LIST_BUSY_BIT, flag);
 	ret = llist_del_first(&pool->clean_list);
 	if (ret)
Index: linux/include/net/netfilter/nf_conntrack.h
===================================================================
--- linux.orig/include/net/netfilter/nf_conntrack.h	2013-12-02 16:07:45.264759422 -0600
+++ linux/include/net/netfilter/nf_conntrack.h	2013-12-02 16:07:45.254759699 -0600
@@ -235,7 +235,7 @@ extern s32 (*nf_ct_nat_offset)(const str
 DECLARE_PER_CPU(struct nf_conn, nf_conntrack_untracked);
 static inline struct nf_conn *nf_ct_untracked_get(void)
 {
-	return &__raw_get_cpu_var(nf_conntrack_untracked);
+	return raw_cpu_ptr(&nf_conntrack_untracked);
 }
 void nf_ct_untracked_status_or(unsigned long bits);
 
Index: linux/include/net/snmp.h
===================================================================
--- linux.orig/include/net/snmp.h	2013-12-02 16:07:45.264759422 -0600
+++ linux/include/net/snmp.h	2013-12-02 16:07:45.254759699 -0600
@@ -170,7 +170,7 @@ struct linux_xfrm_mib {
 
 #define SNMP_ADD_STATS64_BH(mib, field, addend) 			\
 	do {								\
-		__typeof__(*mib[0]) *ptr = __this_cpu_ptr((mib)[0]);	\
+		__typeof__(*mib[0]) *ptr = raw_cpu_ptr((mib)[0]);	\
 		u64_stats_update_begin(&ptr->syncp);			\
 		ptr->mibs[field] += addend;				\
 		u64_stats_update_end(&ptr->syncp);			\
@@ -192,7 +192,7 @@ struct linux_xfrm_mib {
 #define SNMP_UPD_PO_STATS64_BH(mib, basefield, addend)			\
 	do {								\
 		__typeof__(*mib[0]) *ptr;				\
-		ptr = __this_cpu_ptr((mib)[0]);				\
+		ptr = raw_cpu_ptr((mib)[0]);				\
 		u64_stats_update_begin(&ptr->syncp);			\
 		ptr->mibs[basefield##PKTS]++;				\
 		ptr->mibs[basefield##OCTETS] += addend;			\
Index: linux/net/ipv4/route.c
===================================================================
--- linux.orig/net/ipv4/route.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/ipv4/route.c	2013-12-02 16:09:22.000000000 -0600
@@ -1306,7 +1306,7 @@ static bool rt_cache_route(struct fib_nh
 	if (rt_is_input_route(rt)) {
 		p = (struct rtable **)&nh->nh_rth_input;
 	} else {
-		p = (struct rtable **)__this_cpu_ptr(nh->nh_pcpu_rth_output);
+		p = (struct rtable **)raw_cpu_ptr(nh->nh_pcpu_rth_output);
 	}
 	orig = *p;
 
@@ -1932,7 +1932,7 @@ static struct rtable *__mkroute_output(c
 				do_cache = false;
 				goto add;
 			}
-			prth = __this_cpu_ptr(nh->nh_pcpu_rth_output);
+			prth = raw_cpu_ptr(nh->nh_pcpu_rth_output);
 		}
 		rth = rcu_dereference(*prth);
 		if (rt_cache_valid(rth)) {
Index: linux/net/ipv4/tcp.c
===================================================================
--- linux.orig/net/ipv4/tcp.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/ipv4/tcp.c	2013-12-02 16:07:45.254759699 -0600
@@ -2981,7 +2981,7 @@ struct tcp_md5sig_pool *tcp_get_md5sig_p
 	local_bh_disable();
 	p = ACCESS_ONCE(tcp_md5sig_pool);
 	if (p)
-		return __this_cpu_ptr(p);
+		return raw_cpu_ptr(p);
 
 	local_bh_enable();
 	return NULL;
Index: linux/net/ipv4/syncookies.c
===================================================================
--- linux.orig/net/ipv4/syncookies.c	2013-12-02 16:07:45.264759422 -0600
+++ linux/net/ipv4/syncookies.c	2013-12-02 16:07:45.254759699 -0600
@@ -40,7 +40,7 @@ static u32 cookie_hash(__be32 saddr, __b
 
 	net_get_random_once(syncookie_secret, sizeof(syncookie_secret));
 
-	tmp  = __get_cpu_var(ipv4_cookie_scratch);
+	tmp  = this_cpu_ptr(ipv4_cookie_scratch);
 	memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
 	tmp[0] = (__force u32)saddr;
 	tmp[1] = (__force u32)daddr;

Re: [PATCH 17/41] net: Replace __this_cpu_inc in route.c with raw_cpu_inc

[David Miller]

From: Christoph Lameter <cl@linux.com>
Date: Fri, 17 Jan 2014 09:18:29 -0600

> Acked-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Christoph Lameter <cl@linux.com>

Acked-by: David S. Miller <davem@davemloft.net>

Re: [PATCH 24/41] net: Replace get_cpu_var through this_cpu_ptr

[David Miller]

From: Christoph Lameter <cl@linux.com>
Date: Fri, 17 Jan 2014 09:18:36 -0600

> [Patch depends on another patch in this series that introduces raw_cpu_ops]
> 
> Replace uses of get_cpu_var for address calculation through this_cpu_ptr.
> 
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: netdev@vger.kernel.org
> Cc: Eric Dumazet <edumazet@google.com>
> Signed-off-by: Christoph Lameter <cl@linux.com>

Acked-by: David S. Miller <davem@davemloft.net>