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why evthr_pool_start need usleep(5000)? my process often coredump in this function。 about libevhtp HOT 5 OPEN

gamorwang commented on June 13, 2024

why evthr_pool_start need usleep(5000)? my process often coredump in this function。

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Comments (5)

NathanFrench commented on June 13, 2024

If you remove usleep, does it work?

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gamorwang commented on June 13, 2024

I comment this usleep line， then the coredump frequency become bigger.

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NathanFrench commented on June 13, 2024

This is very very hard to reproduce with almost 0 information (your backtrace doesn't even have debug symbols, from what I see, the error is in libevent, not evhtp).

Can you please use the template:

Details

Steps or code to reproduce the problem.

Example code

#include <evhtp.h>

int
main(int argc, char ** argv)
{
    return 0;
}

Version

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gamorwang commented on June 13, 2024

I have found the problem。

step1:
Let your cpu almost 100% use
step2:
remove usleep， then run my example

code:

int j = 0;
vector test_vec;

int main()
{
auto base = event_base_new();
auto ev_htp = evhtp_new(base, NULL);

evhtp_use_threads_wexit(ev_htp, [](evhtp_t * htp, evthr_t * evthr, void * arg) {
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
test_vec.push_back(j++);
}, NULL, 160, NULL);

sleep(10000);
return 0;
}

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gamorwang commented on June 13, 2024

source code 1：

struct evthr_pool {
#ifdef EVTHR_SHARED_PIPE
    int rdr;
    int wdr;
#endif
    int                nthreads;
    evthr_pool_slist_t threads;
};

struct evthr {
    int             rdr;
    int             wdr;
    char            err;
    ev_t          * event;
    evbase_t      * evbase;
    pthread_mutex_t lock;
    pthread_t     * thr;
    evthr_init_cb   init_cb;
    evthr_init_cb   exit_cb;
    void          * arg;
    void          * aux;

#ifdef EVTHR_SHARED_PIPE
    int            pool_rdr;
    struct event * shared_pool_ev;
#endif
    TAILQ_ENTRY(evthr) next;
};

comment：
look at this struct, I think the pthread_mutex_t lock should put into struct evthr_pool, not put into struct evthr.

source code 2：

    pthread_mutex_lock(&thread->lock);
    printf("mutex lock addr: %p\n", &thread->lock);
    if (thread->init_cb != NULL) {
        (thread->init_cb)(thread, thread->arg);
    }
    pthread_mutex_unlock(&thread->lock);