From: Tejun Heo is_sync_wait() is used to distinguish between sync and async waits. Basically sync waits are the ones initialized with init_waitqueue_entry() and async ones with init_waitqueue_func_entry(). The sync/async distinction is used only in prepare_to_wait[_exclusive]() and its only function is to skip setting the current task state if the wait is async. This has a few problems. * No one uses it. None of func_entry users use prepare_to_wait() functions, so the code path never gets executed. * The distinction is bogus. Maybe back when func_entry is used only by aio but it's now also used by epoll and in future possibly by 9p and poll/select. * Taking @state as argument and ignoring it silenly depending on how @wait is initialized is just a bad error-prone API. * It prevents func_entry waits from using wait->private for no good reason. This patch kills is_sync_wait() and the associated code paths from prepare_to_wait[_exclusive](). As there was no user of these code paths, this patch doesn't cause any behavior difference. Signed-off-by: Tejun Heo Acked-by: Ingo Molnar Signed-off-by: Andrew Morton --- include/linux/wait.h | 9 --------- kernel/wait.c | 14 ++------------ 2 files changed, 2 insertions(+), 21 deletions(-) diff -puN include/linux/wait.h~wait-kill-is_sync_wait include/linux/wait.h --- a/include/linux/wait.h~wait-kill-is_sync_wait +++ a/include/linux/wait.h @@ -108,15 +108,6 @@ static inline int waitqueue_active(wait_ return !list_empty(&q->task_list); } -/* - * Used to distinguish between sync and async io wait context: - * sync i/o typically specifies a NULL wait queue entry or a wait - * queue entry bound to a task (current task) to wake up. - * aio specifies a wait queue entry with an async notification - * callback routine, not associated with any task. - */ -#define is_sync_wait(wait) (!(wait) || ((wait)->private)) - extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait); extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait); extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait); diff -puN kernel/wait.c~wait-kill-is_sync_wait kernel/wait.c --- a/kernel/wait.c~wait-kill-is_sync_wait +++ a/kernel/wait.c @@ -72,12 +72,7 @@ prepare_to_wait(wait_queue_head_t *q, wa spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue(q, wait); - /* - * don't alter the task state if this is just going to - * queue an async wait queue callback - */ - if (is_sync_wait(wait)) - set_current_state(state); + set_current_state(state); spin_unlock_irqrestore(&q->lock, flags); } EXPORT_SYMBOL(prepare_to_wait); @@ -91,12 +86,7 @@ prepare_to_wait_exclusive(wait_queue_hea spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) __add_wait_queue_tail(q, wait); - /* - * don't alter the task state if this is just going to - * queue an async wait queue callback - */ - if (is_sync_wait(wait)) - set_current_state(state); + set_current_state(state); spin_unlock_irqrestore(&q->lock, flags); } EXPORT_SYMBOL(prepare_to_wait_exclusive); _