[Bug tapsets/6525] need utrace task-finder-based pid->execname, pid->cwd-path-name tables

[wenji dot huang at oracle dot com]

------- Additional Comments From wenji dot huang at oracle dot com  2009-02-26 09:35 -------
I once tried to implement the functions using task_finder. The basic code is
like the following

#include "task_finder.c"
static char _stp_taskname[TASK_COMM_LEN]="";
static int _stp_process_search_cb(struct stap_task_finder_target *tgt, struct
task_struct *tsk, int register_p, int process_p) {
  if (register_p) { /* found one match */
        if (tsk == NULL) {
                strlcpy(_stp_taskname, "UNKNOWN", MAXSTRINGLEN);
                return 1;
        } else {
                strlcpy(_stp_taskname, tsk->comm, MAXSTRINGLEN);
                return 0;
        }
  }
  return 1;
}

function pid2execname2:string(pid:long) %{ /* pure */
        struct stap_task_finder_target tgt;
        tgt.pathname = NULL;
        tgt.pid = (pid_t)(long)THIS->pid;
        tgt.callback = &_stp_process_search_cb;
        tgt.vm_callback = NULL;
        stap_register_task_finder_target(&tgt);
        stap_start_task_finder();
        strlcpy(THIS->__retvalue, _stp_taskname, MAXSTRINGLEN);
        stap_stop_task_finder();
        CATCH_DEREF_FAULT();
%}

But it can't return the execname of most running processes like init, mingetty,
kjournald because the callback is never invoked.
Only works fine on my forked test process. My box is 2.6.27.9-159.fc10.i686.

Did I miss something or misunderstand the mechanism?


-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6525

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