JNI AttachCurrentThread

Question

希望你今天过得愉快。

我有一个JNI so库，其中包含以下代码。

static JavaVM *  s_vm = NULL;   // The VM pointer

// The following exported method is called by JVM when this so is loaded
JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved)
{
    s_vm = vm;
    return JNI_VERSION_1_6;
}


// And a native thread is created to fire Java method
apr_thread_t * thread;
apr_threadattr_t * attr;
apr_threadattr_create( &attr, pool);
apr_threadattr_detach_set( attr, 1);
apr_threadattr_stacksize_set( attr, 1024 * 1024 * 10);
apr_thread_create( &thread, attr, receive_thread, pool, pool);

// within the created thread, the following method is called somehow
void onMsgReceived(const char * replyChannel, const unsigned char * ctrl, uint32_t ctrlLen, const unsigned char * payload, uint32_t payloadLen)
{
    JNIEnv * env = NULL;

    int env_stat = s_vm->GetEnv((void **)&env, JNI_VERSION_1_6);
    if (env_stat == JNI_EDETACHED) {
        if (s_vm->AttachCurrentThread((void **) &env, NULL) != 0) { // <--  this line crashes
            return;
        }
    } else if (env_stat == JNI_OK) {
    } else if (env_stat == JNI_EVERSION) {
        return;
    }


    if (env_stat == JNI_EDETACHED)
        s_vm->DetachCurrentThread();
}

我将一个调试器附加到进程，它是AttachCurrentThread在JVM中导致SEGFAULT。调用JNI_OnLoad时，s_vm的值相同。

奇怪的是，相同的代码在Windows上运行，但在CentOS6.5上运行失败 我也尝试了与Windows上相同的JRE版本，但问题仍然存在。

Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

我不确定这是否是由多个GLIBC版本引起的？

$objdump -p ./libinterop_d.so 

./libinterop_d.so:     file format elf64-x86-64

Program Header:
    LOAD off    0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**21
         filesz 0x0000000000071b70 memsz 0x0000000000071b70 flags r-x
    LOAD off    0x0000000000072000 vaddr 0x0000000000272000 paddr 0x0000000000272000 align 2**21
         filesz 0x0000000000003358 memsz 0x0000000000015be8 flags rw-
 DYNAMIC off    0x0000000000073a70 vaddr 0x0000000000273a70 paddr 0x0000000000273a70 align 2**3
         filesz 0x00000000000001c0 memsz 0x00000000000001c0 flags rw-
    NOTE off    0x00000000000001c8 vaddr 0x00000000000001c8 paddr 0x00000000000001c8 align 2**2
         filesz 0x0000000000000024 memsz 0x0000000000000024 flags r--
     TLS off    0x0000000000072000 vaddr 0x0000000000272000 paddr 0x0000000000272000 align 2**3
         filesz 0x0000000000000000 memsz 0x0000000000000010 flags r--
EH_FRAME off    0x0000000000065814 vaddr 0x0000000000065814 paddr 0x0000000000065814 align 2**2
         filesz 0x000000000000201c memsz 0x000000000000201c flags r--
   STACK off    0x0000000000000000 vaddr 0x0000000000000000 paddr 0x0000000000000000 align 2**3
         filesz 0x0000000000000000 memsz 0x0000000000000000 flags rw-

Dynamic Section:
  NEEDED               librt.so.1
  NEEDED               libm.so.6
  NEEDED               libpthread.so.0
  NEEDED               libc.so.6
  NEEDED               ld-linux-x86-64.so.2
  INIT                 0x000000000001eb40
  FINI                 0x000000000005c4e8
  GNU_HASH             0x00000000000001f0
  STRTAB               0x0000000000009900
  SYMTAB               0x00000000000026a0
  STRSZ                0x000000000000d351
  SYMENT               0x0000000000000018
  PLTGOT               0x0000000000273fd8
  PLTRELSZ             0x00000000000037c8
  PLTREL               0x0000000000000007
  JMPREL               0x000000000001b378
  RELA                 0x00000000000176d0
  RELASZ               0x0000000000003ca8
  RELAENT              0x0000000000000018
  VERNEED              0x00000000000175e0
  VERNEEDNUM           0x0000000000000005
  VERSYM               0x0000000000016c52
  RELACOUNT            0x00000000000000ee

Version References:
  required from librt.so.1:
    0x09691a75 0x00 10 GLIBC_2.2.5
  required from libm.so.6:
    0x09691a75 0x00 09 GLIBC_2.2.5
  required from ld-linux-x86-64.so.2:
    0x0d696913 0x00 06 GLIBC_2.3
  required from libc.so.6:
    0x0d696919 0x00 11 GLIBC_2.9
    0x09691973 0x00 08 GLIBC_2.3.3
    0x0d696914 0x00 07 GLIBC_2.4
    0x0d696913 0x00 05 GLIBC_2.3
    0x09691a75 0x00 04 GLIBC_2.2.5
  required from libpthread.so.0:
    0x09691a75 0x00 03 GLIBC_2.2.5
    0x0d696914 0x00 02 GLIBC_2.4

更新：我发现如果从项目中移除lanterna，一切正常。但是如果我将lanterna jar添加到项目中，即使没有代码可以调用它，也会发生这种情况。

lanterna与JNI不相容？

Answer 1

最后，我避免使用从pthread或apr创建的线程来绕过这个问题。并使用Java线程调用方法并阻塞，直到有东西要返回。