src/jdk.hotspot.agent/linux/native/libsaproc/libproc_impl.c

*** 26,35 ****
--- 26,37 ----
  #include <stdlib.h>
  #include <string.h>
  #include <fcntl.h>
  #ifdef INCLUDE_SA_ATTACH
  #include <thread_db.h>
+ #else
+ #include <dirent.h>
  #endif
  #include "libproc_impl.h"
  
  #define SA_ALTROOT "SA_ALTROOT"
  
*** 302,314 ****
    if (ptr->callback(ptr->ph, ti.ti_tid, ti.ti_lid) != true)
      return TD_ERR;
  
    return TD_OK;
  }
  
! // read thread_info using libthread_db
  bool read_thread_info(struct ps_prochandle* ph, thread_info_callback cb) {
    struct thread_db_client_data mydata;
    td_thragent_t* thread_agent = NULL;
    if (td_ta_new(ph, &thread_agent) != TD_OK) {
       print_debug("can't create libthread_db agent\n");
       return false;
--- 304,319 ----
    if (ptr->callback(ptr->ph, ti.ti_tid, ti.ti_lid) != true)
      return TD_ERR;
  
    return TD_OK;
  }
+ #endif // INCLUDE_SA_ATTACH
  
! // read thread_info using libthread_db or by iterating through the entries
! // in /proc/<pid>/task/
  bool read_thread_info(struct ps_prochandle* ph, thread_info_callback cb) {
+ #ifdef INCLUDE_SA_ATTACH
    struct thread_db_client_data mydata;
    td_thragent_t* thread_agent = NULL;
    if (td_ta_new(ph, &thread_agent) != TD_OK) {
       print_debug("can't create libthread_db agent\n");
       return false;
*** 325,337 ****
       return false;
    }
  
    // delete thread agent
    td_ta_delete(thread_agent);
    return true;
  }
- #endif // INCLUDE_SA_ATTACH
  
  // get number of threads
  int get_num_threads(struct ps_prochandle* ph) {
     return ph->num_threads;
  }
--- 330,365 ----
       return false;
    }
  
    // delete thread agent
    td_ta_delete(thread_agent);
+ #else
+   DIR *dir = NULL;
+   struct dirent *ent = NULL;
+   char taskpath[80];
+   pid_t pid = ph->pid;
+ 
+   // Find the lwpids to attach to by traversing the /proc/<pid>/task/ directory.
+   snprintf(taskpath, sizeof (taskpath), "/proc/%ld/task", (unsigned long)pid);
+   if ((dir = opendir(taskpath)) != NULL) {
+     while ((ent = readdir(dir)) != NULL) {
+       unsigned long lwp;
+ 
+       if ((lwp = strtoul(ent->d_name, NULL, 10)) != 0) {
+         // Create and add the thread info.
+         (*cb)(ph, 0, lwp);
+       }
+     }
+   } else {
+     print_debug("Could not open /proc/%ld/task.\n", (unsigned long)pid);
+     return false;
+   }
+ 
+   closedir(dir);
+ #endif
    return true;
  }
  
  // get number of threads
  int get_num_threads(struct ps_prochandle* ph) {
     return ph->num_threads;
  }