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

程序鏈接了DPDK庫，啟動就出錯，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

分析發現，C語言定義了constructor屬性的函數會先於main()執行，DPDK中定義了RTE_INIT()宏，用來聲明一個如構造函數:

#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中定義了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); \
}

然后用定義了很多初始化構造函數，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)

出錯原因是涉及到的constructor函數代碼有多個實例，被重復調用。我遇到的實例是因為有重復靜態鏈接：app鏈接了libxxx.a和librte_*.a, 並且libxxx.a也鏈接了librte_*.a，app里面就有兩份librte_*.a的代碼實例。

解決方法：把靜態鏈接librte_*.a都改成動態鏈接librte_*.so

 

另：加入log，可發現在main()函數之前調用了很多EAL_REGISTER_TAILQ()函數:

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