diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/fork.c | 17 | ||||
| -rw-r--r-- | kernel/locking/osq_lock.c | 13 | ||||
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 27 |
3 files changed, 52 insertions, 5 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index eb30711e7d44..5a90b0f6d668 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1366,6 +1366,18 @@ static struct task_struct *copy_process(unsigned long clone_flags, cpufreq_task_times_init(p); + /* + * This _must_ happen before we call free_task(), i.e. before we jump + * to any of the bad_fork_* labels. This is to avoid freeing + * p->set_child_tid which is (ab)used as a kthread's data pointer for + * kernel threads (PF_KTHREAD). + */ + p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; + /* + * Clear TID on mm_release()? + */ + p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; + ftrace_graph_init_task(p); rt_mutex_init_task(p); @@ -1527,11 +1539,6 @@ static struct task_struct *copy_process(unsigned long clone_flags, } } - p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; - /* - * Clear TID on mm_release()? - */ - p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL; #ifdef CONFIG_BLOCK p->plug = NULL; #endif diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c index 05a37857ab55..8d7047ecef4e 100644 --- a/kernel/locking/osq_lock.c +++ b/kernel/locking/osq_lock.c @@ -104,6 +104,19 @@ bool osq_lock(struct optimistic_spin_queue *lock) prev = decode_cpu(old); node->prev = prev; + + /* + * osq_lock() unqueue + * + * node->prev = prev osq_wait_next() + * WMB MB + * prev->next = node next->prev = prev // unqueue-C + * + * Here 'node->prev' and 'next->prev' are the same variable and we need + * to ensure these stores happen in-order to avoid corrupting the list. + */ + smp_wmb(); + WRITE_ONCE(prev->next, node); /* diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a4d4de05b2d1..1be33caf157d 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -511,6 +511,33 @@ struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem) unsigned long flags; /* + * __rwsem_down_write_failed_common(sem) + * rwsem_optimistic_spin(sem) + * osq_unlock(sem->osq) + * ... + * atomic_long_add_return(&sem->count) + * + * - VS - + * + * __up_write() + * if (atomic_long_sub_return_release(&sem->count) < 0) + * rwsem_wake(sem) + * osq_is_locked(&sem->osq) + * + * And __up_write() must observe !osq_is_locked() when it observes the + * atomic_long_add_return() in order to not miss a wakeup. + * + * This boils down to: + * + * [S.rel] X = 1 [RmW] r0 = (Y += 0) + * MB RMB + * [RmW] Y += 1 [L] r1 = X + * + * exists (r0=1 /\ r1=0) + */ + smp_rmb(); + + /* * If a spinner is present, it is not necessary to do the wakeup. * Try to do wakeup only if the trylock succeeds to minimize * spinlock contention which may introduce too much delay in the |