Fix softlockup by removing the wait_queue flag: WQ_FLAG_BOOKMARK.
The commit b0b598ee08f9 (filemap: remove use of wait bookmarks) said the overly long list of waiters on a locked page was solved by commit: 9a1ea439b16b ("mm: put_and_wait_on_page_locked() while page is migrated").
But actually the problem was solved by another commit: 3510ca20ece0 ("Minor page waitqueue cleanups"), so we can remove the bookmark flag now to solve the softlockup problem.
Changes in V3: - fixed incorrect mainline patch adaptation: wake_fags -> wake_flags. - Readapt __wake_up_common_lock()
Changes in V2: - modified the commit message.
Matthew Wilcox (Oracle) (2): filemap: remove use of wait bookmarks sched: remove wait bookmarks
include/linux/wait.h | 3 --- kernel/sched/wait.c | 57 ++++++-------------------------------------- mm/filemap.c | 21 +--------------- 3 files changed, 8 insertions(+), 73 deletions(-)
From: "Matthew Wilcox (Oracle)" willy@infradead.org
mainline inclusion from mainline-v6.7-rc1 commit b0b598ee08f9759b70971e297cf7ddd3eaaa5245 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I93S7P CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
--------------------------------
The original problem of the overly long list of waiters on a locked page was solved properly by commit 9a1ea439b16b ("mm: put_and_wait_on_page_locked() while page is migrated"). In the meantime, using bookmarks for the writeback bit can cause livelocks, so we need to stop using them.
Link: https://lkml.kernel.org/r/20231010035829.544242-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: Bin Lai sclaibin@gmail.com Cc: Benjamin Segall bsegall@google.com Cc: Daniel Bristot de Oliveira bristot@redhat.com Cc: Dietmar Eggemann dietmar.eggemann@arm.com Cc: Ingo Molnar mingo@redhat.com Cc: Juri Lelli juri.lelli@redhat.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Mel Gorman mgorman@suse.de Cc: Peter Zijlstra peterz@infradead.org Cc: Steven Rostedt (Google) rostedt@goodmis.org Cc: Valentin Schneider vschneid@redhat.com Cc: Vincent Guittot vincent.guittot@linaro.org
Cc: Ingo Molnar mingo@kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Zizhi Wo wozizhi@huawei.com
Conflicts: mm/filemap.c --- mm/filemap.c | 21 +-------------------- 1 file changed, 1 insertion(+), 20 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c index ecf8bed4c76f..ba0f08e2ef97 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1124,32 +1124,13 @@ static void wake_up_page_bit(struct page *page, int bit_nr) wait_queue_head_t *q = page_waitqueue(page); struct wait_page_key key; unsigned long flags; - wait_queue_entry_t bookmark;
key.page = page; key.bit_nr = bit_nr; key.page_match = 0;
- bookmark.flags = 0; - bookmark.private = NULL; - bookmark.func = NULL; - INIT_LIST_HEAD(&bookmark.entry); - spin_lock_irqsave(&q->lock, flags); - __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); - - while (bookmark.flags & WQ_FLAG_BOOKMARK) { - /* - * Take a breather from holding the lock, - * allow pages that finish wake up asynchronously - * to acquire the lock and remove themselves - * from wait queue - */ - spin_unlock_irqrestore(&q->lock, flags); - cpu_relax(); - spin_lock_irqsave(&q->lock, flags); - __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark); - } + __wake_up_locked_key(q, TASK_NORMAL, &key);
/* * It is possible for other pages to have collided on the waitqueue
From: "Matthew Wilcox (Oracle)" willy@infradead.org
mainline inclusion from mainline-v6.7-rc1 commit 37acade0ce8938f00d6979bd02b8043b5b7089ae category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I93S7P CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
--------------------------------
There are no users of wait bookmarks left, so simplify the wait code by removing them.
Link: https://lkml.kernel.org/r/20231010035829.544242-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Acked-by: Ingo Molnar mingo@kernel.org Cc: Benjamin Segall bsegall@google.com Cc: Bin Lai sclaibin@gmail.com Cc: Daniel Bristot de Oliveira bristot@redhat.com Cc: Dietmar Eggemann dietmar.eggemann@arm.com Cc: Ingo Molnar mingo@redhat.com Cc: Juri Lelli juri.lelli@redhat.com Cc: Mel Gorman mgorman@suse.de Cc: Peter Zijlstra peterz@infradead.org Cc: Steven Rostedt (Google) rostedt@goodmis.org Cc: Valentin Schneider vschneid@redhat.com Cc: Vincent Guittot vincent.guittot@linaro.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Zizhi Wo wozizhi@huawei.com
Conflicts: include/linux/wait.h kernel/sched/wait.c --- include/linux/wait.h | 3 --- kernel/sched/wait.c | 55 ++++---------------------------------------- 2 files changed, 5 insertions(+), 53 deletions(-)
diff --git a/include/linux/wait.h b/include/linux/wait.h index 60a62d3adbe6..8dca17c0dc20 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -19,7 +19,6 @@ int default_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, int /* wait_queue_entry::flags */ #define WQ_FLAG_EXCLUSIVE 0x01 #define WQ_FLAG_WOKEN 0x02 -#define WQ_FLAG_BOOKMARK 0x04
/* * A single wait-queue entry structure: @@ -199,8 +198,6 @@ __remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq
void __wake_up(struct wait_queue_head *wq_head, unsigned int mode, int nr, void *key); void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, void *key); -void __wake_up_locked_key_bookmark(struct wait_queue_head *wq_head, - unsigned int mode, void *key, wait_queue_entry_t *bookmark); void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode, int nr, void *key); void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr); void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode, int nr); diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c index 021da4812fca..78587e892579 100644 --- a/kernel/sched/wait.c +++ b/kernel/sched/wait.c @@ -46,13 +46,6 @@ void remove_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry } EXPORT_SYMBOL(remove_wait_queue);
-/* - * Scan threshold to break wait queue walk. - * This allows a waker to take a break from holding the - * wait queue lock during the wait queue walk. - */ -#define WAITQUEUE_WALK_BREAK_CNT 64 - /* * The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just * wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve @@ -63,21 +56,13 @@ EXPORT_SYMBOL(remove_wait_queue); * zero in this (rare) case, and we handle it by continuing to scan the queue. */ static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode, - int nr_exclusive, int wake_flags, void *key, - wait_queue_entry_t *bookmark) + int nr_exclusive, int wake_flags, void *key) { wait_queue_entry_t *curr, *next; - int cnt = 0;
lockdep_assert_held(&wq_head->lock);
- if (bookmark && (bookmark->flags & WQ_FLAG_BOOKMARK)) { - curr = list_next_entry(bookmark, entry); - - list_del(&bookmark->entry); - bookmark->flags = 0; - } else - curr = list_first_entry(&wq_head->head, wait_queue_entry_t, entry); + curr = list_first_entry(&wq_head->head, wait_queue_entry_t, entry);
if (&curr->entry == &wq_head->head) return nr_exclusive; @@ -86,21 +71,11 @@ static int __wake_up_common(struct wait_queue_head *wq_head, unsigned int mode, unsigned flags = curr->flags; int ret;
- if (flags & WQ_FLAG_BOOKMARK) - continue; - ret = curr->func(curr, mode, wake_flags, key); if (ret < 0) break; if (ret && (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) break; - - if (bookmark && (++cnt > WAITQUEUE_WALK_BREAK_CNT) && - (&next->entry != &wq_head->head)) { - bookmark->flags = WQ_FLAG_BOOKMARK; - list_add_tail(&bookmark->entry, &next->entry); - break; - } }
return nr_exclusive; @@ -110,23 +85,10 @@ static void __wake_up_common_lock(struct wait_queue_head *wq_head, unsigned int int nr_exclusive, int wake_flags, void *key) { unsigned long flags; - wait_queue_entry_t bookmark; - - bookmark.flags = 0; - bookmark.private = NULL; - bookmark.func = NULL; - INIT_LIST_HEAD(&bookmark.entry);
spin_lock_irqsave(&wq_head->lock, flags); - nr_exclusive = __wake_up_common(wq_head, mode, nr_exclusive, wake_flags, key, &bookmark); + __wake_up_common(wq_head, mode, nr_exclusive, wake_flags, key); spin_unlock_irqrestore(&wq_head->lock, flags); - - while (bookmark.flags & WQ_FLAG_BOOKMARK) { - spin_lock_irqsave(&wq_head->lock, flags); - nr_exclusive = __wake_up_common(wq_head, mode, nr_exclusive, - wake_flags, key, &bookmark); - spin_unlock_irqrestore(&wq_head->lock, flags); - } }
/** @@ -151,23 +113,16 @@ EXPORT_SYMBOL(__wake_up); */ void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr) { - __wake_up_common(wq_head, mode, nr, 0, NULL, NULL); + __wake_up_common(wq_head, mode, nr, 0, NULL); } EXPORT_SYMBOL_GPL(__wake_up_locked);
void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, void *key) { - __wake_up_common(wq_head, mode, 1, 0, key, NULL); + __wake_up_common(wq_head, mode, 1, 0, key); } EXPORT_SYMBOL_GPL(__wake_up_locked_key);
-void __wake_up_locked_key_bookmark(struct wait_queue_head *wq_head, - unsigned int mode, void *key, wait_queue_entry_t *bookmark) -{ - __wake_up_common(wq_head, mode, 1, 0, key, bookmark); -} -EXPORT_SYMBOL_GPL(__wake_up_locked_key_bookmark); - /** * __wake_up_sync_key - wake up threads blocked on a waitqueue. * @wq_head: the waitqueue
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