diff options
| -rw-r--r-- | runtime/ChangeLog | 8 | ||||
| -rw-r--r-- | runtime/task_finder.c | 58 |
2 files changed, 43 insertions, 23 deletions
diff --git a/runtime/ChangeLog b/runtime/ChangeLog index 6da5814c..796b9cca 100644 --- a/runtime/ChangeLog +++ b/runtime/ChangeLog @@ -1,3 +1,11 @@ +2008-06-30 David Smith <dsmith@redhat.com> + + * task_finder.c (stap_utrace_detach_ops): Removed check to see if + thread has a mm (in the case where a thread isn't quite dead + yet). + (stap_utrace_attach): Minor error handling improvement. + (__stp_utrace_attach_match_tsk): Ditto. + 2008-06-24 David Smith <dsmith@redhat.com> From: Srinivasa DS <srinivasa@in.ibm.com> diff --git a/runtime/task_finder.c b/runtime/task_finder.c index 07610864..021144dc 100644 --- a/runtime/task_finder.c +++ b/runtime/task_finder.c @@ -149,30 +149,37 @@ stap_utrace_detach_ops(struct utrace_engine_ops *ops) long error = 0; pid_t pid = 0; + // Notice we're not calling get_task_mm() in this loop. In + // every other instance when calling do_each_thread, we avoid + // tasks with no mm, because those are kernel threads. So, + // why is this function different? When a thread is in the + // process of dying, its mm gets freed. Then, later the + // thread gets in the dying state and the thread's + // UTRACE_EVENT(DEATH) event handler gets called (if any). + // + // If a thread is in this "mortally wounded" state - no mm + // but not dead - and at that moment this function is called, + // we'd miss detaching from it if we were checking to see if + // it had an mm. + rcu_read_lock(); do_each_thread(grp, tsk) { - struct mm_struct *mm; - - if (tsk->pid <= 1) + if (tsk == NULL || tsk->pid <= 1) continue; - mm = get_task_mm(tsk); - if (mm) { - mmput(mm); - engine = utrace_attach(tsk, UTRACE_ATTACH_MATCH_OPS, - ops, 0); - if (IS_ERR(engine)) { - error = -PTR_ERR(engine); - if (error != ENOENT) { - pid = tsk->pid; - goto udo_err; - } - error = 0; - } - else if (engine != NULL) { - utrace_detach(tsk, engine); - debug_task_finder_detach(); + engine = utrace_attach(tsk, UTRACE_ATTACH_MATCH_OPS, + ops, 0); + if (IS_ERR(engine)) { + error = -PTR_ERR(engine); + if (error != ENOENT) { + pid = tsk->pid; + goto udo_err; } + error = 0; + } + else if (engine != NULL) { + utrace_detach(tsk, engine); + debug_task_finder_detach(); } } while_each_thread(grp, tsk); udo_err: @@ -276,7 +283,7 @@ stap_utrace_attach(struct task_struct *tsk, int rc = 0; // Ignore init - if (tsk->pid <= 1) + if (tsk == NULL || tsk->pid <= 1) return EPERM; // Ignore threads with no mm (which are kernel threads). @@ -300,8 +307,12 @@ stap_utrace_attach(struct task_struct *tsk, rc = EFAULT; } else { - utrace_set_flags(tsk, engine, event_flags); - debug_task_finder_attach(); + rc = utrace_set_flags(tsk, engine, event_flags); + if (rc == 0) + debug_task_finder_attach(); + else + _stp_error("utrace_set_flags returned error %d on pid %d", + rc, (int)tsk->pid); } return rc; } @@ -392,7 +403,8 @@ __stp_utrace_attach_match_tsk(struct task_struct *path_tsk, char *mmpath_buf; char *mmpath; - if (path_tsk->pid <= 1 || match_tsk->pid <= 1) + if (path_tsk == NULL || path_tsk->pid <= 1 + || match_tsk == NULL || match_tsk->pid <= 1) return; /* Grab the path associated with the path_tsk. */ |