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    Subject[PATCH] [NET]: Fix Ooops of napi net_rx_action.
    Date
    [NET]: Fix Ooops of napi net_rx_action.
    Before doing list_move_tail napi poll_list, it should be ensured

    Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
    ---
    diff --git a/net/core/dev.c b/net/core/dev.c
    index 86d6261..74bd5ab 100644
    --- a/net/core/dev.c
    +++ b/net/core/dev.c
    @@ -2207,7 +2207,8 @@ static void net_rx_action(struct softirq_action *h)
    * still "owns" the NAPI instance and therefore can
    * move the instance around on the list at-will.
    */
    - if (unlikely(work == weight))
    + if (unlikely((test_bit(NAPI_STATE_SCHED, &n->state))
    + && (work == weight)))
    list_move_tail(&n->poll_list, list);

    netpoll_poll_unlock(have);
    ---
    I was able to make it real oops on 2.6.24-rc4 + e1000 napi + smp.
    eth0 of my laptop is connected directly to a packet generator.
    The packet generator is making unicast udp packets to laptop (approximately 70000pps).
    At that time, if the interface is went down, Ooops occurred.
    Thanks.
    Joonwoo


    root@joonwpark-laptop:~# ifconfig eth0 down
    BUG: unable to handle kernel paging request at virtual address 00100104
    printing eip: c42ecc35 *pdpt = 000000001fc89001 *pde = 0000000000000000
    Ooops: 0002 [#1] SMP
    Modules linked in:
    Pid: 4, comm:ksoftirqd/0 Not tainted (2.6.24-rc4 #27)
    EIP: 0060:[<c42ecc35>] EFLAGS: 00010046 CPU: 0
    EIP is at net_rx_action+0x1d5/0x1f0
    EAX: 00100100 EBX: f77c965c ECX: 00000000 EDX: 00200200
    ESI: 00000040 EDI: f77c965c EBP: f7c6df94 ESP: f7c6df64
    DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
    Process ksoftirqd/0 (pid: 4, ti=f7c6c000 task=f7c68ab0 task.ti=f7c6c000)
    Stack: 00000002 00000001 c42ecabe c4598f40 c1d0f5cc 0000c7da 000000ac f77c965c
    00000040 00000001 c4543b18 c4598f40 f7c6dfb0 c4032a07 00000004 00000000
    00000246 00000000 c4032f60 f7c6dfbc c4032ad7 c459ba80 f6c6dfcc c4032fb9
    Call Trace:
    [<c40053ca>] show_trace_log_lvl+0x1a/0x30
    [<c4005489>] show_stack_log_lvl+0xa9/0xd0
    [<c400557a>] show_registers+0xca/0x1c0
    [<c4005785>] die+0x115/0x230
    [<c4020f0c>] do_page_fault+0x34c/0x7f0
    [<c43c9cea>] error_code+0x72/0x78
    [<c4032a07>] __do_softirq+0x87/0x60
    [<c4032ad7>] do_softirq+0x57/0xe0
    [<c4041ee2>] kthread+0x42/0x70
    [<c4004fc3>] kernel_thread_helper+0x7/0x14
    gdb outputs
    (gdb) info line *net_rx_action+0x1d5
    Line 157 of "include/linux/list.h"
    starts at address 0xc42ecc35 <net_rx_action+469>
    and ends at 0xc42ecc38 <net_rx_action+472>.
    (gdb) l include/linux/list.h:157
    152 * This is only for internal list manipulation where we know
    153 * the prev/next entries already!
    154 */
    155 static inline void __list_del(struct list_head * prev, struct list_head * next)
    156 {
    157 next->prev = prev;
    158 prev->next = next;
    159 }
    160
    161 /**
    (gdb) info line *__do_softirq+0x87
    Line 130 of "include/linux/rcupdate.h"
    starts at address 0xc4032a07 <__do_softirq+135>
    and ends at 0xc4032a0a <__do_softirq+138>.
    (gdb) l include/linux/rcupdate.h:130
    125 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
    126 rdp->passed_quiesc = 1;
    127 }
    128 static inline void rcu_bh_qsctr_inc(int cpu)
    129 {
    130 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
    131 rdp->passed_quiesc = 1;
    132 }
    133
    134 extern int rcu_pending(int cpu);
    (gdb) info line *do_softirq+0x57
    Line 269 of "kernel/softirq.c" starts at address 0xc4032ad2 <do_softirq+82>
    and ends at 0xc4032ae0 <tasklet_kill>.
    (gdb) l kernel/softirq.c:269
    264 local_irq_save(flags);
    265
    266 pending = local_softirq_pending();
    267
    268 if (pending)
    269 __do_softirq();
    270
    271 local_irq_restore(flags);
    272 }
    273


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