From 2055da97389a605c8a00d163d40903afbe413921 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 20 Jun 2017 12:06:46 +0200 Subject: sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming So I've noticed a number of instances where it was not obvious from the code whether ->task_list was for a wait-queue head or a wait-queue entry. Furthermore, there's a number of wait-queue users where the lists are not for 'tasks' but other entities (poll tables, etc.), in which case the 'task_list' name is actively confusing. To clear this all up, name the wait-queue head and entry list structure fields unambiguously: struct wait_queue_head::task_list => ::head struct wait_queue_entry::task_list => ::entry For example, this code: rqw->wait.task_list.next != &wait->task_list ... is was pretty unclear (to me) what it's doing, while now it's written this way: rqw->wait.head.next != &wait->entry ... which makes it pretty clear that we are iterating a list until we see the head. Other examples are: list_for_each_entry_safe(pos, next, &x->task_list, task_list) { list_for_each_entry(wq, &fence->wait.task_list, task_list) { ... where it's unclear (to me) what we are iterating, and during review it's hard to tell whether it's trying to walk a wait-queue entry (which would be a bug), while now it's written as: list_for_each_entry_safe(pos, next, &x->head, entry) { list_for_each_entry(wq, &fence->wait.head, entry) { Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- fs/userfaultfd.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index bda64fcd8a0c..6148ccd6cccf 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -129,7 +129,7 @@ static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, * wouldn't be enough, the smp_mb__before_spinlock is * enough to avoid an explicit smp_mb() here. */ - list_del_init(&wq->task_list); + list_del_init(&wq->entry); out: return ret; } @@ -522,13 +522,13 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason) * and it's fine not to block on the spinlock. The uwq on this * kernel stack can be released after the list_del_init. */ - if (!list_empty_careful(&uwq.wq.task_list)) { + if (!list_empty_careful(&uwq.wq.entry)) { spin_lock(&ctx->fault_pending_wqh.lock); /* * No need of list_del_init(), the uwq on the stack * will be freed shortly anyway. */ - list_del(&uwq.wq.task_list); + list_del(&uwq.wq.entry); spin_unlock(&ctx->fault_pending_wqh.lock); } @@ -869,7 +869,7 @@ static inline struct userfaultfd_wait_queue *find_userfault_in( if (!waitqueue_active(wqh)) goto out; /* walk in reverse to provide FIFO behavior to read userfaults */ - wq = list_last_entry(&wqh->task_list, typeof(*wq), task_list); + wq = list_last_entry(&wqh->head, typeof(*wq), entry); uwq = container_of(wq, struct userfaultfd_wait_queue, wq); out: return uwq; @@ -1003,14 +1003,14 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, * changes __remove_wait_queue() to use * list_del_init() in turn breaking the * !list_empty_careful() check in - * handle_userfault(). The uwq->wq.task_list + * handle_userfault(). The uwq->wq.head list * must never be empty at any time during the * refile, or the waitqueue could disappear * from under us. The "wait_queue_head_t" * parameter of __remove_wait_queue() is unused * anyway. */ - list_del(&uwq->wq.task_list); + list_del(&uwq->wq.entry); __add_wait_queue(&ctx->fault_wqh, &uwq->wq); write_seqcount_end(&ctx->refile_seq); @@ -1032,7 +1032,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, fork_nctx = (struct userfaultfd_ctx *) (unsigned long) uwq->msg.arg.reserved.reserved1; - list_move(&uwq->wq.task_list, &fork_event); + list_move(&uwq->wq.entry, &fork_event); spin_unlock(&ctx->event_wqh.lock); ret = 0; break; @@ -1069,8 +1069,8 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, if (!list_empty(&fork_event)) { uwq = list_first_entry(&fork_event, typeof(*uwq), - wq.task_list); - list_del(&uwq->wq.task_list); + wq.entry); + list_del(&uwq->wq.entry); __add_wait_queue(&ctx->event_wqh, &uwq->wq); userfaultfd_event_complete(ctx, uwq); } @@ -1752,12 +1752,12 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) unsigned long pending = 0, total = 0; spin_lock(&ctx->fault_pending_wqh.lock); - list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) { + list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { uwq = container_of(wq, struct userfaultfd_wait_queue, wq); pending++; total++; } - list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) { + list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { uwq = container_of(wq, struct userfaultfd_wait_queue, wq); total++; } -- cgit v1.2.3-55-g7522