DPDK程序初始化遇到"tailq is already registered"错误

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程序链接了DPDK库，启动就出错，打出如下信息：

EAL: UIO_RESOURCE_LIST tailq is already registered
PANIC in tailqinitfn_rte_uio_tailq():
Cannot initialize tailq: UIO_RESOURCE_LIST

分析发现，C语言定义constructor属性的函数会先于main()执行，DPDK中定义了RTE_INIT()宏，用来声明一个如构造函数:

#define RTE_PRIO(prio) \
    RTE_PRIORITY_ ## prio

/**
 * Run function before main() with high priority.
 *
 * @param func
 *   Constructor function.
 * @param prio
 *   Priority number must be above 100.
 *   Lowest number is the first to run.
 */
#ifndef RTE_INIT_PRIO /* Allow to override from EAL */
#define RTE_INIT_PRIO(func, prio) \
static void __attribute__((constructor(RTE_PRIO(prio)), used)) func(void)
#endif

/**
 * Run function before main() with low priority.
 *
 * The constructor will be run after prioritized constructors.
 *
 * @param func
 *   Constructor function.
 */
#define RTE_INIT(func) \
    RTE_INIT_PRIO(func, LAST)

在tailq.h中定义了EAL_REGISTER_TAILQ()

/**
 * Register a tail queue.
 *
 * Register a tail queue from shared memory.
 * This function is mainly used by EAL_REGISTER_TAILQ macro which is used to
 * register tailq from the different dpdk libraries. Since this macro is a
 * constructor, the function has no access to dpdk shared memory, so the
 * registered tailq can not be used before call to rte_eal_init() which calls
 * rte_eal_tailqs_init().
 *
 * @param t
 *   The tailq element which contains the name of the tailq you want to
 *   create (/retrieve when in secondary process).
 * @return
 *   0 on success or -1 in case of an error.
 */
int rte_eal_tailq_register(struct rte_tailq_elem *t);

#define EAL_REGISTER_TAILQ(t) \
RTE_INIT(tailqinitfn_ ##t) \
{ \
    if (rte_eal_tailq_register(&t) < 0) \
        rte_panic("Cannot initialize tailq: %s\n", t.name); \
}

然后用定义了很多初始化构造函数，比如rte_ring.c中:

#define RTE_TAILQ_RING_NAME "RTE_RING"

static struct rte_tailq_elem rte_ring_tailq = {
    .name = RTE_TAILQ_RING_NAME,
};
EAL_REGISTER_TAILQ(rte_ring_tailq)

所以原因是涉及到的constructor函数代码有多个实例，被重复调用。我遇到的实例是因为有重复静态链接：app链接了libxxx.a和librte_*.a, 并且libxxx.a也链接了librte_*.a，app里面就有两份librte_*.a的代码实例。

解决方法：把静态链接librte_*.a都改成动态链接librte_*.so

加入log，可发现在main()函数之前调用了很多EAL_REGISTER_TAILQ()函数:

EAL: rte_eal_tailq_register: name=RTE_RING
EAL: rte_eal_tailq_register: name=RTE_MEMPOOL
EAL: rte_eal_tailq_register: name=RTE_MBUF_DYNFIELD
EAL: rte_eal_tailq_register: name=RTE_MBUF_DYNFLAG
EAL: rte_eal_tailq_register: name=RTE_HASH
EAL: rte_eal_tailq_register: name=RTE_FBK_HASH
EAL: rte_eal_tailq_register: name=RTE_THASH
EAL: rte_eal_tailq_register: name=RTE_ACL
EAL: rte_eal_tailq_register: name=RTE_DIST_BURST
EAL: rte_eal_tailq_register: name=RTE_DISTRIBUTOR
EAL: rte_eal_tailq_register: name=RTE_EFD
EAL: rte_eal_tailq_register: name=RTE_KNI
EAL: rte_eal_tailq_register: name=RTE_LPM
EAL: rte_eal_tailq_register: name=RTE_LPM6
EAL: rte_eal_tailq_register: name=RTE_MEMBER
EAL: rte_eal_tailq_register: name=RTE_RIB
EAL: rte_eal_tailq_register: name=RTE_RIB6
EAL: rte_eal_tailq_register: name=RTE_REORDER
EAL: rte_eal_tailq_register: name=RTE_STACK
EAL: rte_eal_tailq_register: name=RTE_IPSEC_SAD
EAL: rte_eal_tailq_register: name=RTE_FIB
EAL: rte_eal_tailq_register: name=RTE_FIB6

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