diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/fork.c | 31 | ||||
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 44 |
2 files changed, 59 insertions, 16 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 099b89978dd3..17389e9935c4 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -953,6 +953,15 @@ static void mm_init_aio(struct mm_struct *mm) #endif } +static __always_inline void mm_clear_owner(struct mm_struct *mm, + struct task_struct *p) +{ +#ifdef CONFIG_MEMCG + if (mm->owner == p) + WRITE_ONCE(mm->owner, NULL); +#endif +} + static void mm_init_owner(struct mm_struct *mm, struct task_struct *p) { #ifdef CONFIG_MEMCG @@ -1332,6 +1341,7 @@ static struct mm_struct *dup_mm(struct task_struct *tsk) free_pt: /* don't put binfmt in mmput, we haven't got module yet */ mm->binfmt = NULL; + mm_init_owner(mm, NULL); mmput(mm); fail_nomem: @@ -1663,6 +1673,21 @@ static inline void rcu_copy_process(struct task_struct *p) #endif /* #ifdef CONFIG_TASKS_RCU */ } +static void __delayed_free_task(struct rcu_head *rhp) +{ + struct task_struct *tsk = container_of(rhp, struct task_struct, rcu); + + free_task(tsk); +} + +static __always_inline void delayed_free_task(struct task_struct *tsk) +{ + if (IS_ENABLED(CONFIG_MEMCG)) + call_rcu(&tsk->rcu, __delayed_free_task); + else + free_task(tsk); +} + /* * This creates a new process as a copy of the old one, * but does not actually start it yet. @@ -2124,8 +2149,10 @@ bad_fork_cleanup_io: bad_fork_cleanup_namespaces: exit_task_namespaces(p); bad_fork_cleanup_mm: - if (p->mm) + if (p->mm) { + mm_clear_owner(p->mm, p); mmput(p->mm); + } bad_fork_cleanup_signal: if (!(clone_flags & CLONE_THREAD)) free_signal_struct(p->signal); @@ -2156,7 +2183,7 @@ bad_fork_cleanup_count: bad_fork_free: p->state = TASK_DEAD; put_task_stack(p); - free_task(p); + delayed_free_task(p); fork_out: spin_lock_irq(¤t->sighand->siglock); hlist_del_init(&delayed.node); diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 50d9af615dc4..115860164c36 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -130,6 +130,7 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, { struct rwsem_waiter *waiter, *tmp; long oldcount, woken = 0, adjustment = 0; + struct list_head wlist; /* * Take a peek at the queue head waiter such that we can determine @@ -188,18 +189,42 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, * of the queue. We know that woken will be at least 1 as we accounted * for above. Note we increment the 'active part' of the count by the * number of readers before waking any processes up. + * + * We have to do wakeup in 2 passes to prevent the possibility that + * the reader count may be decremented before it is incremented. It + * is because the to-be-woken waiter may not have slept yet. So it + * may see waiter->task got cleared, finish its critical section and + * do an unlock before the reader count increment. + * + * 1) Collect the read-waiters in a separate list, count them and + * fully increment the reader count in rwsem. + * 2) For each waiters in the new list, clear waiter->task and + * put them into wake_q to be woken up later. */ - list_for_each_entry_safe(waiter, tmp, &sem->wait_list, list) { - struct task_struct *tsk; - + list_for_each_entry(waiter, &sem->wait_list, list) { if (waiter->type == RWSEM_WAITING_FOR_WRITE) break; woken++; - tsk = waiter->task; + } + list_cut_before(&wlist, &sem->wait_list, &waiter->list); + + adjustment = woken * RWSEM_ACTIVE_READ_BIAS - adjustment; + if (list_empty(&sem->wait_list)) { + /* hit end of list above */ + adjustment -= RWSEM_WAITING_BIAS; + } + + if (adjustment) + atomic_long_add(adjustment, &sem->count); + + /* 2nd pass */ + list_for_each_entry_safe(waiter, tmp, &wlist, list) { + struct task_struct *tsk; + tsk = waiter->task; get_task_struct(tsk); - list_del(&waiter->list); + /* * Ensure calling get_task_struct() before setting the reader * waiter to nil such that rwsem_down_read_failed() cannot @@ -215,15 +240,6 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, /* wake_q_add() already take the task ref */ put_task_struct(tsk); } - - adjustment = woken * RWSEM_ACTIVE_READ_BIAS - adjustment; - if (list_empty(&sem->wait_list)) { - /* hit end of list above */ - adjustment -= RWSEM_WAITING_BIAS; - } - - if (adjustment) - atomic_long_add(adjustment, &sem->count); } /* |