diff options
Diffstat (limited to 'include/linux/sched')
| -rw-r--r-- | include/linux/sched/signal.h | 7 | ||||
| -rw-r--r-- | include/linux/sched/task.h | 38 |
2 files changed, 39 insertions, 6 deletions
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 669e8cff40c7..0014d3adaf84 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -649,12 +649,9 @@ extern void flush_itimer_signals(void); extern bool current_is_single_threaded(void); /* - * Careful: do_each_thread/while_each_thread is a double loop so - * 'break' will not work as expected - use goto instead. + * Without tasklist/siglock it is only rcu-safe if g can't exit/exec, + * otherwise next_thread(t) will never reach g after list_del_rcu(g). */ -#define do_each_thread(g, t) \ - for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do - #define while_each_thread(g, t) \ while ((t = next_thread(t)) != g) diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index dd35ce28bb90..a23af225c898 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -118,11 +118,47 @@ static inline struct task_struct *get_task_struct(struct task_struct *t) } extern void __put_task_struct(struct task_struct *t); +extern void __put_task_struct_rcu_cb(struct rcu_head *rhp); static inline void put_task_struct(struct task_struct *t) { - if (refcount_dec_and_test(&t->usage)) + if (!refcount_dec_and_test(&t->usage)) + return; + + /* + * In !RT, it is always safe to call __put_task_struct(). + * Under RT, we can only call it in preemptible context. + */ + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) { + static DEFINE_WAIT_OVERRIDE_MAP(put_task_map, LD_WAIT_SLEEP); + + lock_map_acquire_try(&put_task_map); __put_task_struct(t); + lock_map_release(&put_task_map); + return; + } + + /* + * under PREEMPT_RT, we can't call put_task_struct + * in atomic context because it will indirectly + * acquire sleeping locks. + * + * call_rcu() will schedule delayed_put_task_struct_rcu() + * to be called in process context. + * + * __put_task_struct() is called when + * refcount_dec_and_test(&t->usage) succeeds. + * + * This means that it can't "conflict" with + * put_task_struct_rcu_user() which abuses ->rcu the same + * way; rcu_users has a reference so task->usage can't be + * zero after rcu_users 1 -> 0 transition. + * + * delayed_free_task() also uses ->rcu, but it is only called + * when it fails to fork a process. Therefore, there is no + * way it can conflict with put_task_struct(). + */ + call_rcu(&t->rcu, __put_task_struct_rcu_cb); } DEFINE_FREE(put_task, struct task_struct *, if (_T) put_task_struct(_T)) |