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SubjectRe: linux-2.6.12-rc1-mm4-RT-V0.7.42-08
From
Date
Hi Ingo,

I need the following two patches to keep my system alive and avoid
the BUGs in the log send to you earlier (private mail).

------------------- example BUG ------------------------

BUG: using smp_processor_id() in preemptible [00000001] code: java/16460
caller is icmp_send+0x9b/0x3d0
[<c020b1db>] smp_processor_id+0x9b/0xb0 (8)
[<c032246b>] icmp_send+0x9b/0x3d0 (28)
[<c013ae67>] check_wakeup_timing+0x47/0x160 (8)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (40)
[<c014d159>] kmem_cache_free+0x39/0x120 (8)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (12)
[<c014d159>] kmem_cache_free+0x39/0x120 (8)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (24)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (28)
[<c0276066>] rtl8139_start_xmit+0x86/0x1d0 (8)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (40)
[<c02f3259>] qdisc_restart+0x1b9/0x230 (8)
[<c02f3259>] qdisc_restart+0x1b9/0x230 (36)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (8)
[<c02760ae>] rtl8139_start_xmit+0xce/0x1d0 (16)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (32)
[<c02ffe33>] ip_fragment+0x663/0x7f0 (60)
[<c013138f>] rcu_read_unlock+0x5f/0x70 (32)
[<c02f9d2a>] __ip_route_output_key+0xba/0xe0 (8)
[<c02fe950>] ip_finish_output+0x0/0x2f0 (16)
[<c02ff383>] ip_queue_xmit+0x263/0x590 (24)
[<c02ff383>] ip_queue_xmit+0x263/0x590 (20)
[<c03102eb>] tcp_transmit_skb+0x38b/0x750 (196)
[<c031113e>] tcp_write_xmit+0x10e/0x2f0 (56)
[<c03054ab>] tcp_sendmsg+0xffb/0x1050 (52)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (12)
[<c013b9c5>] unqueue_me+0x25/0x130 (8)
[<c0325f4a>] inet_sendmsg+0x4a/0x70 (92)
[<c02dd795>] sock_aio_write+0x135/0x150 (24)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (88)
[<c0163c69>] do_sync_write+0xb9/0x110 (20)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (44)
[<c0164d52>] fget_light+0x62/0x90 (8)
[<c034269d>] _raw_spin_unlock+0xd/0x30 (44)
[<c0134c50>] autoremove_wake_function+0x0/0x50 (8)
[<c0163d9b>] vfs_write+0xdb/0x170 (52)
[<c0163ee1>] sys_write+0x41/0x70 (24)
[<c0102f0b>] sysenter_past_esp+0x54/0x75 (28)
---------------------------
| preempt count: 00000002 ]
| 2-level deep critical section nesting:
----------------------------------------
.. [<c03422e6>] .... _raw_spin_lock+0x16/0x90
.....[<00000000>] .. ( <= 0x0)
.. [<c03422e6>] .... _raw_spin_lock+0x16/0x90
.....[<00000000>] .. ( <= 0x0)


--
Peter Zijlstra <a.p.zijlstra@chello.nl>


Since there is no lock held yet we are still preemptable; and since
icmp_socket is a per cpu variable switching cpus gives weird results.


Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>


--- /usr/src/linux-2.6.12-rc1-mm4-RT-V0.7.42-08/net/ipv4/icmp.c~ 2005-03-25 10:14:32.000000000 +0100
+++ /usr/src/linux-2.6.12-rc1-mm4-RT-V0.7.42-08/net/ipv4/icmp.c 2005-04-02 18:58:19.000000000 +0200
@@ -376,8 +376,8 @@

static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
- struct sock *sk = icmp_socket->sk;
- struct inet_sock *inet = inet_sk(sk);
+ struct sock *sk;
+ struct inet_sock *inet;
struct ipcm_cookie ipc;
struct rtable *rt = (struct rtable *)skb->dst;
u32 daddr;
@@ -388,6 +388,9 @@
if (icmp_xmit_lock())
return;

+ sk = icmp_socket->sk;
+ inet = inet_sk(sk);
+
icmp_param->data.icmph.checksum = 0;
icmp_out_count(icmp_param->data.icmph.type);

Since on PREEMPT_RT spinlocks allow preemption, it's possible to
change cpu at (almost) any point in time. Make sure we stick to
the per cpu variable we started with.


Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>


--- /usr/src/linux-2.6.12-rc1-mm4-RT-V0.7.42-08/net/ipv4/icmp_orig.c 2005-04-03 00:09:08.000000000 +0200
+++ /usr/src/linux-2.6.12-rc1-mm4-RT-V0.7.42-08/net/ipv4/icmp.c 2005-04-03 00:20:22.000000000 +0200
@@ -228,27 +228,32 @@
*
* On SMP we have one ICMP socket per-cpu.
*/
-static DEFINE_PER_CPU(struct socket *, __icmp_socket) = NULL;
-#define icmp_socket __get_cpu_var(__icmp_socket)
+static DEFINE_PER_CPU_LOCKED(struct socket *, __icmp_socket) = NULL;

static __inline__ struct socket * icmp_xmit_lock(int cpu)
{
+ struct socket *icmp_socket;
+
local_bh_disable();
+ icmp_socket = get_cpu_var_locked(__icmp_socket, cpu);

if (unlikely(!spin_trylock(&icmp_socket->sk->sk_lock.slock))) {
/* This can happen if the output path signals a
* dst_link_failure() for an outgoing ICMP packet.
*/
+ put_cpu_var_locked(__icmp_socket, cpu);
local_bh_enable();
- return 1;
+ return NULL;
}

- return 0;
+ return icmp_socket;
}

static void icmp_xmit_unlock(int cpu)
{
+ struct socket *icmp_socket = __get_cpu_var_locked(__icmp_socket, cpu);
spin_unlock_bh(&icmp_socket->sk->sk_lock.slock);
+ put_cpu_var_locked(__icmp_socket, cpu);
}

/*
@@ -345,7 +350,8 @@
}

static void icmp_push_reply(struct icmp_bxm *icmp_param,
- struct ipcm_cookie *ipc, struct rtable *rt)
+ struct ipcm_cookie *ipc, struct rtable *rt,
+ struct socket *icmp_socket)
{
struct sk_buff *skb;

@@ -377,16 +383,19 @@

static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
{
+ struct socket *icmp_socket;
struct sock *sk;
struct inet_sock *inet;
struct ipcm_cookie ipc;
struct rtable *rt = (struct rtable *)skb->dst;
u32 daddr;
+ int cpu;

if (ip_options_echo(&icmp_param->replyopts, skb))
goto out;

- if (icmp_xmit_lock())
+ cpu = _smp_processor_id();
+ if (!(icmp_socket = icmp_xmit_lock(cpu)))
return;

sk = icmp_socket->sk;
@@ -414,10 +423,10 @@
}
if (icmpv4_xrlim_allow(rt, icmp_param->data.icmph.type,
icmp_param->data.icmph.code))
- icmp_push_reply(icmp_param, &ipc, rt);
+ icmp_push_reply(icmp_param, &ipc, rt, icmp_socket);
ip_rt_put(rt);
out_unlock:
- icmp_xmit_unlock();
+ icmp_xmit_unlock(cpu);
out:;
}

@@ -435,8 +444,9 @@

void icmp_send(struct sk_buff *skb_in, int type, int code, u32 info)
{
+ struct socket *icmp_socket;
struct iphdr *iph;
- int room;
+ int room, cpu;
struct icmp_bxm icmp_param;
struct rtable *rt = (struct rtable *)skb_in->dst;
struct ipcm_cookie ipc;
@@ -507,7 +517,8 @@
}
}

- if (icmp_xmit_lock())
+ cpu = _smp_processor_id();
+ if (!(icmp_socket = icmp_xmit_lock(cpu)))
return;

/*
@@ -580,11 +591,11 @@
icmp_param.data_len = room;
icmp_param.head_len = sizeof(struct icmphdr);

- icmp_push_reply(&icmp_param, &ipc, rt);
+ icmp_push_reply(&icmp_param, &ipc, rt, icmp_socket);
ende:
ip_rt_put(rt);
out_unlock:
- icmp_xmit_unlock();
+ icmp_xmit_unlock(cpu);
out:;
}

@@ -1116,20 +1127,20 @@
continue;

err = sock_create_kern(PF_INET, SOCK_RAW, IPPROTO_ICMP,
- &per_cpu(__icmp_socket, i));
+ &__get_cpu_var_locked(__icmp_socket, i));

if (err < 0)
panic("Failed to create the ICMP control socket.\n");

- per_cpu(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC;
+ __get_cpu_var_locked(__icmp_socket, i)->sk->sk_allocation = GFP_ATOMIC;

/* Enough space for 2 64K ICMP packets, including
* sk_buff struct overhead.
*/
- per_cpu(__icmp_socket, i)->sk->sk_sndbuf =
+ __get_cpu_var_locked(__icmp_socket, i)->sk->sk_sndbuf =
(2 * ((64 * 1024) + sizeof(struct sk_buff)));

- inet = inet_sk(per_cpu(__icmp_socket, i)->sk);
+ inet = inet_sk(__get_cpu_var_locked(__icmp_socket, i)->sk);
inet->uc_ttl = -1;
inet->pmtudisc = IP_PMTUDISC_DONT;

@@ -1137,7 +1148,7 @@
* see it, we do not wish this socket to see incoming
* packets.
*/
- per_cpu(__icmp_socket, i)->sk->sk_prot->unhash(per_cpu(__icmp_socket, i)->sk);
+ __get_cpu_var_locked(__icmp_socket, i)->sk->sk_prot->unhash(__get_cpu_var_locked(__icmp_socket, i)->sk);
}
}
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