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Message-ID: <1288267354.2649.369.camel@edumazet-laptop>
Date: Thu, 28 Oct 2010 14:02:34 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: "Tantilov, Emil S" <emil.s.tantilov@...el.com>
Cc: David Miller <davem@...emloft.net>,
"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>,
"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
"Brattain, Ross B" <ross.b.brattain@...el.com>,
netdev <netdev@...r.kernel.org>
Subject: [PATCH] ixgbe: delay rx_ring freeing
Le jeudi 28 octobre 2010 à 06:24 +0200, Eric Dumazet a écrit :
> Le mercredi 27 octobre 2010 à 16:35 -0600, Tantilov, Emil S a écrit :
> > Eric,
> >
> > We are seeing intermittent hangs on ia32 arch which seem to point to this patch:
> >
> > BUG: unable to handle kernel NULL pointer dereference at 00000040
> > IP: [<f7f6b537>] ixgbe_get_stats64+0x47/0x120 [ixgbe]
> > *pdpt = 000000002dc83001 *pde = 000000032d7e5067
> > Oops: 0000 [#2] SMP
> > last sysfs file: /sys/devices/system/cpu/cpu23/cache/index2/shared_cpu_map
> > Modules linked in: act_skbedit cls_u32 sch_multiq ixgbe mdio netconsole configfs autofs4 8021q garp stp llc sunrpc ipv6 e
> > xt3 jbd dm_mirror dm_region_hash dm_log dm_round_robin dm_multipath power_meter hwmon sg ses enclosure dcdbas pcspkr serio_raw iTCO_wdt iTCO_vendor_support io
> > atdma dca i7core_edac edac_core bnx2 ext4 mbcache jbd2 sr_mod cdrom sd_mod crc_t10dif pata_acpi ata_generic ata_piix megaraid_sas dm_mod [last unloaded: mperf
> > ]
> >
> > Pid: 1939, comm: irqbalance Tainted: G D W 2.6.36-rc7-upstream-net-next-2.6-ixgbe-queue-i386-g55e1a84 #1 09CGW2/Po
> > werEdge T610
> > EIP: 0060:[<f7f6b537>] EFLAGS: 00010206 CPU: 0
> > EIP is at ixgbe_get_stats64+0x47/0x120 [ixgbe]
> > EAX: 00000000 EBX: ecc45e4c ECX: ebea0400 EDX: 00000000
> > ESI: ebea0000 EDI: 00000018 EBP: f7f846a0 ESP: ecc45d88
> > DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
> > Process irqbalance (pid: 1939, ti=ecc44000 task=efc63a50 task.ti=ecc44000)
> > Stack:
> > ecc45e4c 00000000 ebea0400 ebea0000 ecc45e4c ebea0000 ecc45f04 f7f846a0
> > <0> c0750593 ebea0000 edfec340 ebea0000 000002b5 c075063a edfec340 c0993eec
> > <0> ebe78000 0000021c 00000000 00000009 00000000 00000000 00000000 00000000
> > Call Trace:
> > [<c0750593>] ? dev_get_stats+0x33/0xc0
> > [<c075063a>] ? dev_seq_printf_stats+0x1a/0x180
> > [<c07507aa>] ? dev_seq_show+0xa/0x20
> > [<c052398f>] ? seq_read+0x22f/0x3d0
> > [<c0523760>] ? seq_read+0x0/0x3d0
> > [<c054fdde>] ? proc_reg_read+0x5e/0x90
> > [<c054fd80>] ? proc_reg_read+0x0/0x90
> > [<c050a1dd>] ? vfs_read+0x9d/0x160
> > [<c049d4ef>] ? audit_syscall_entry+0x20f/0x230
> > [<c050a971>] ? sys_read+0x41/0x70
> > [<c0409cdf>] ? sysenter_do_call+0x12/0x28
> > Code: 60 4f 7e c8 8b 44 24 08 8b b8 20 06 00 00 85 ff 7e 63 c7 44 24 04 00 00 00 00 66 90 8b 54 24 04 8b 4c 24 08 8b 84 9
> > 1 00 05 00 00 <8b> 50 40 eb 06 8d 74 26 00 89 ca f6 c2 01 0f 85 ae 00 00 00 8b
> > EIP: [<f7f6b537>] ixgbe_get_stats64+0x47/0x120 [ixgbe] SS:ESP 0068:ecc45d88
> > CR2: 0000000000000040
> > ---[ end trace 51ea89f4e57f54f1 ]---
> >
> > Emil
I believe I now understand the problem, please try following patch.
Thanks
[PATCH] ixgbe: delay rx_ring freeing
"cat /proc/net/dev" uses RCU protection only.
Its quite possible we call a driver get_stats() method while device is
dismantling and freeing its data structures.
So get_stats() methods must be very careful not accessing driver private
data without appropriate locking.
In ixgbe case, we access rx_ring pointers. These pointers are freed in
ixgbe_clear_interrupt_scheme() and set to NULL, this can trigger NULL
dereference in ixgbe_get_stats64()
A possible fix is to use RCU locking in ixgbe_get_stats64() and defer
rx_ring freeing after a grace period in ixgbe_clear_interrupt_scheme()
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Reported-by: Tantilov, Emil S <emil.s.tantilov@...el.com>
---
drivers/net/ixgbe/ixgbe.h | 1
drivers/net/ixgbe/ixgbe_main.c | 34 +++++++++++++++++++++----------
2 files changed, 25 insertions(+), 10 deletions(-)
diff --git a/drivers/net/ixgbe/ixgbe.h b/drivers/net/ixgbe/ixgbe.h
index ed8703c..018e143 100644
--- a/drivers/net/ixgbe/ixgbe.h
+++ b/drivers/net/ixgbe/ixgbe.h
@@ -192,6 +192,7 @@ struct ixgbe_ring {
unsigned int size; /* length in bytes */
dma_addr_t dma; /* phys. address of descriptor ring */
+ struct rcu_head rcu;
} ____cacheline_internodealigned_in_smp;
enum ixgbe_ring_f_enum {
diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
index f856312..1b16292 100644
--- a/drivers/net/ixgbe/ixgbe_main.c
+++ b/drivers/net/ixgbe/ixgbe_main.c
@@ -4742,6 +4742,11 @@ err_set_interrupt:
return err;
}
+static void ring_free_rcu(struct rcu_head *head)
+{
+ kfree(container_of(head, struct ixgbe_ring, rcu));
+}
+
/**
* ixgbe_clear_interrupt_scheme - Clear the current interrupt scheme settings
* @adapter: board private structure to clear interrupt scheme on
@@ -4758,7 +4763,12 @@ void ixgbe_clear_interrupt_scheme(struct ixgbe_adapter *adapter)
adapter->tx_ring[i] = NULL;
}
for (i = 0; i < adapter->num_rx_queues; i++) {
- kfree(adapter->rx_ring[i]);
+ struct ixgbe_ring *ring = adapter->rx_ring[i];
+
+ /* ixgbe_get_stats64() might access this ring, we must wait
+ * a grace period before freeing it.
+ */
+ call_rcu(&ring->rcu, ring_free_rcu);
adapter->rx_ring[i] = NULL;
}
@@ -6551,20 +6561,23 @@ static struct rtnl_link_stats64 *ixgbe_get_stats64(struct net_device *netdev,
/* accurate rx/tx bytes/packets stats */
dev_txq_stats_fold(netdev, stats);
+ rcu_read_lock();
for (i = 0; i < adapter->num_rx_queues; i++) {
- struct ixgbe_ring *ring = adapter->rx_ring[i];
+ struct ixgbe_ring *ring = ACCESS_ONCE(adapter->rx_ring[i]);
u64 bytes, packets;
unsigned int start;
- do {
- start = u64_stats_fetch_begin_bh(&ring->syncp);
- packets = ring->stats.packets;
- bytes = ring->stats.bytes;
- } while (u64_stats_fetch_retry_bh(&ring->syncp, start));
- stats->rx_packets += packets;
- stats->rx_bytes += bytes;
+ if (ring) {
+ do {
+ start = u64_stats_fetch_begin_bh(&ring->syncp);
+ packets = ring->stats.packets;
+ bytes = ring->stats.bytes;
+ } while (u64_stats_fetch_retry_bh(&ring->syncp, start));
+ stats->rx_packets += packets;
+ stats->rx_bytes += bytes;
+ }
}
-
+ rcu_read_unlock();
/* following stats updated by ixgbe_watchdog_task() */
stats->multicast = netdev->stats.multicast;
stats->rx_errors = netdev->stats.rx_errors;
@@ -7270,6 +7283,7 @@ static void __exit ixgbe_exit_module(void)
dca_unregister_notify(&dca_notifier);
#endif
pci_unregister_driver(&ixgbe_driver);
+ rcu_barrier(); /* Wait for completion of call_rcu()'s */
}
#ifdef CONFIG_IXGBE_DCA
--
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