huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?

这段话可能是来自 Linux 内核的调试信息。其中 %u %s %p %08x 都是占位符，用于打印不同类型的变量值。其中，“%u”表示一个无符号整数，"%s" 表示一个字符串，"%p" 表示一个指针，"%08x" 表示一个 8 位十六进制数。

这段信息的意思是：内核中的软中断被触发了，同时打印出了相应的信息。在进入软中断时，记录了当前的抢占计数器值（preempt_count），并在退出时再次记录了这个值。这个值用于确保在处理软中断期间不会被抢占。

相关问题

第一幕： 旁白: (male protagonist) No matter how complicated the outside world is, it has nothing to do with a broken heart. Pei Zhi: Chen Ning! Chen Ning: Huh? What's wrong? Pei Zhi: There’s a group event after class today . Chen Ning: I already know that and I will definitely go. Pei Zhi: Okay, let's go together. [Chen Ning glanced back at Lu Bai]: Lu Bai, will you go to next week's dinner? [glanced up at Chen Ning]: I’m not interested. Chen Ning: Why not go? Why don't you participate in all class activities? Lu Bai: I'm not interested. Chen Ning: I just hope you can contact us more... Lu Bai: No. 【Get up and leave】 Qu Yanting: Okay Chen Ning, he never goes to this kind of activity, don't persuade you. Narrator: [Lu Bai] I'm not rejecting her, I'm just rejecting the world.

Act 1:

Narrator: "No matter how complicated the outside world may seem, it has nothing to do with a broken heart."

Pei Zhi: "Chen Ning!"

Chen Ning: "Yes?"

Pei Zhi: "There's a group event after class today. Are you going?"

Chen Ning: "Of course, I'm definitely going."

Pei Zhi: "Great, let's go together."

[Chen Ning glances back at Lu Bai]

Chen Ning: "Lu Bai, will you come to the dinner next week?"

[Lu Bai looks up at Chen Ning]

Lu Bai: "I'm not interested."

Chen Ning: "Why not? Why don't you participate in any of the class activities?"

Lu Bai: "I'm just not interested."

Chen Ning: "I just hope you can hang out with us more."

Lu Bai: "No."

[Lu Bai gets up and leaves]

Qu Yanting: "It's okay Chen Ning. Lu Bai never goes to these kinds of activities. Don't try to persuade him."

Narrator: [Lu Bai] "I'm not rejecting her, I'm just rejecting the world."

struct sk_buff结构体解析

`struct sk_buff` 是 Linux 内核中用来表示网络数据包的数据结构。它是一个很重要的数据结构，因为 Linux 内核中网络协议栈的所有数据包处理都是基于 sk_buff 进行的。

下面是 `struct sk_buff` 结构体的定义：

struct sk_buff {
    struct sk_buff *next;
    struct sk_buff *prev;

    ktime_t tstamp;

    struct sock *sk;
    struct net_device *dev;
    char cb[48];

    unsigned int len;
    unsigned int data_len;
    __u16 mac_len;
    __u16 hdr_len;
    union {
        __u16 all;
        struct {
            __u16 nfmark : 16;
        } nfctmark;
        struct {
            __u16 pkt_type : 3;
            __u16 ignore_df : 1;
            __u16 nf_trace : 1;
            __u16 ip_summed : 2;
            __u16 ooo_okay : 1;
            __u16 l4_rxhash : 1;
            __u16 sw_hash : 1;
            __u16 sw_hash_valid : 1;
            __u16 l5_hash_valid : 1;
            __u16 l4_hash_valid : 1;
            __u16 fclone : 2;
            __u16 frag_list : 2;
            __u16 rxhash : 1;
            __u16 loopback : 1;
            __u16 vlan_present : 1;
            __u16 vlan_tci : 16;
            __u16 inner_protocol : 16;
            __u16 inner_transport_header : 16;
        } parsed;
    } encapsulation;

    unsigned char protocol;
    unsigned char pkt_type: 3;
    unsigned char fclone: 2;
    unsigned char ip_summed: 2;
    unsigned char ooo_okay: 1;

    __u16 vlan_proto;
    __u16 vlan_tci;

    union {
        struct {
            __be16 h_vlan_TCI;
            __be16 h_vlan_encapsulated_proto;
        };
        __be32 ipv4;
        struct ipv6hdr *ipv6h;
        struct arphdr *arph;
        struct tcphdr *hth;
        struct udphdr *huh;
        struct icmphdr *icmph;
    } protocol_headers;

    union {
        struct tcphdr *th;
        struct udphdr *uh;
        struct icmphdr *icmph;
        struct igmphdr *igmph;
        struct iphdr *iph;
        struct ipv6hdr *ipv6h;
        struct arphdr *arph;
        struct pppox_hdr *pppoe;
        struct snap_header *llc;
        struct cfm_pdu_header *cfm_pdu;
        struct batadv_unicast_packet *batman_adv;
        struct batadv_bcast_packet *batman_adv_bcast;
        struct batadv_icmp_packet *batman_adv_icmp;
        struct batadv_tvlv_packet *batman_adv_tvlv;
        struct batadv_frag_packet *batman_adv_frag;
        struct batadv_purge_packet *batman_adv_purge;
        struct batadv_gw_packet *batman_adv_gw;
        struct batadv_tt_change_packet *batman_adv_tt_change;
        struct batadv_mcast_packet *batman_adv_mcast;
        struct batadv_frag_list *batman_adv_frag_list;
        struct batadv_unicast_4addr_packet *batman_adv_unicast_4addr;
        struct batadv_bla_claim *batman_adv_bla_claim;
        struct batadv_bla_backbone_gw *batman_adv_bla_backbone_gw;
        struct batadv_bla_claim_reply *batman_adv_bla_claim_reply;
        struct batadv_bla_claim_confirm *batman_adv_bla_claim_confirm;
        struct batadv_bla_claim_ack *batman_adv_bla_claim_ack;
        struct batadv_bla_update *batman_adv_bla_update;
        struct batadv_bla_claim_broadcast *batman_adv_bla_claim_broadcast;
        struct batadv_bla_claim_broadcast_reply *batman_adv_bla_claim_broadcast_reply;
    } encapsulated;

    char *head;
    char *data;
    char *tail;
    char *end;

    unsigned int truesize;
    atomic_t users;
};

`struct sk_buff` 结构体中的字段含义如下：

- `next` 和 `prev`：`struct sk_buff` 是一个双向链表，这两个字段用于链表操作；
- `tstamp`：时间戳，用于记录数据包的接收或发送时间；
- `sk`：指向网络套接字的指针；
- `dev`：指向网络设备的指针；
- `cb`：可选的控制块，用于保存一些协议栈内部使用的数据；
- `len`：数据包的总长度；
- `data_len`：数据包实际负载的长度；
- `mac_len`：物理层帧头的长度；
- `hdr_len`：网络层协议头的长度；
- `encapsulation`：封装信息，用于保存协议头的解析结果；
- `protocol`：网络协议号；
- `pkt_type`：数据包类型；
- `fclone`：用于指示是否进行数据包复制；
- `ip_summed`：用于指示是否需要计算 IP 校验和；
- `ooo_okay`：用于指示是否允许乱序到达的数据包；
- `vlan_proto` 和 `vlan_tci`：VLAN 标签的协议号和标识符；
- `protocol_headers`：协议头指针的联合体；
- `encapsulated`：封装协议的联合体；
- `head`：指向数据包缓冲区首地址的指针；
- `data`：指向数据包负载首地址的指针；
- `tail`：指向数据包负载末地址的指针；
- `end`：指向数据包缓冲区末地址的指针；
- `truesize`：数据包缓冲区的实际大小；
- `users`：用于记录当前正在使用该数据包的线程数的原子计数器。