Message ID | 1288267354.2649.369.camel@edumazet-laptop |
---|---|
State | Awaiting Upstream, archived |
Delegated to: | David Miller |
Headers | show |
On Thu, 2010-10-28 at 05:02 -0700, Eric Dumazet wrote: > 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@gmail.com> > Reported-by: Tantilov, Emil S <emil.s.tantilov@intel.com> > --- > drivers/net/ixgbe/ixgbe.h | 1 > drivers/net/ixgbe/ixgbe_main.c | 34 +++++++++++++++++++++---------- > 2 files changed, 25 insertions(+), 10 deletions(-) > Thanks Eric, I have added this patch to my queue.
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