Messages in this thread |  | | Subject | Re: [PATCH v2] locking/hung_task: Show all hung tasks before panic | From | Tetsuo Handa <> | Date | Sat, 7 Apr 2018 21:31:19 +0900 |
| |
Hello.
Can we add lockdep functions which print trace of threads with locks held?
For example,
void debug_show_map_users(struct lockdep_map *map) { struct task_struct *g, *p; struct held_lock *hlock; int i, depth;
rcu_read_lock(); for_each_process_thread(g, p) { depth = p->lockdep_depth; hlock = p->held_locks; for (i = 0; i < depth; i++) if (map == hlock[i]->instance) { touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); sched_show_task(p); lockdep_print_held_locks(p); break; } } rcu_read_unlock(); }
is for replacing debug_show_all_locks() in oom_reap_task() because we are interested in only threads holding specific mm->mmap_sem.
For example
void debug_show_relevant_tasks(struct task_struct *origin) { struct task_struct *g, *p; struct held_lock *i_hlock, *j_hlock; int i, j, i_depth, j_depth;
rcu_read_lock(); i_depth = origin->lockdep_depth; i_hlock = origin->held_locks; for_each_process_thread(g, p) { j_depth = p->lockdep_depth; j_hlock = p->held_locks; for (i = 0; i < i_depth; i++) for (j = 0; j < j_depth; j++) if (i_hlock[i]->instance == j_hlock[j]->instance) goto hit; continue; hit: touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); sched_show_task(p); lockdep_print_held_locks(p); } rcu_read_unlock(); }
or
void debug_show_all_locked_tasks(void) { struct task_struct *g, *p;
rcu_read_lock(); for_each_process_thread(g, p) { if (p->lockdep_depth == 0) continue; touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); sched_show_task(p); lockdep_print_held_locks(p); } rcu_read_unlock(); }
are for replacing debug_show_all_locks() in check_hung_task() for cases like https://syzkaller.appspot.com/bug?id=26aa22915f5e3b7ca2cfca76a939f12c25d624db because we are interested in only threads holding locks.
SysRq-t is too much but SysRq-w is useless for killable/interruptible threads...
|  |