From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@kernel.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH] mm: silence soft lockups from unlock_page
Date: Fri, 24 Jul 2020 17:24:25 +0200 [thread overview]
Message-ID: <20200724152424.GC17209@redhat.com> (raw)
In-Reply-To: <CAHk-=wgvGOnMF0ePU4xS236bOsP8jouj3rps+ysCaGXvCjh2Dg@mail.gmail.com>
On 07/23, Linus Torvalds wrote:
>
> But I'll walk over my patch mentally one more time. Here's the current
> version, anyway.
Both patches look correct to me, feel free to add
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
> @@ -1013,18 +1014,40 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync,
> if (wait_page->bit_nr != key->bit_nr)
> return 0;
>
> + /* Stop walking if it's locked */
> + if (wait->flags & WQ_FLAG_EXCLUSIVE) {
> + if (test_and_set_bit(key->bit_nr, &key->page->flags))
> + return -1;
> + } else {
> + if (test_bit(key->bit_nr, &key->page->flags))
> + return -1;
> + }
not sure this makes any sense, but this looks like another user of
trylock_page_bit_common(), see the patch below on top of 1/2.
Oleg.
--- mm/filemap.c~ 2020-07-24 17:09:34.728133846 +0200
+++ mm/filemap.c 2020-07-24 17:23:52.279185374 +0200
@@ -1000,6 +1000,14 @@
wait_queue_entry_t wait;
};
+static int trylock_page_bit_common(struct page *page, int bit_nr,
+ struct wait_queue_entry *wait)
+{
+ return wait->flags & WQ_FLAG_EXCLUSIVE ?
+ !test_and_set_bit(bit_nr, &page->flags) :
+ !test_bit(bit_nr, &page->flags);
+}
+
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
{
int ret;
@@ -1015,13 +1023,8 @@
return 0;
/* Stop walking if it's locked */
- if (wait->flags & WQ_FLAG_EXCLUSIVE) {
- if (test_and_set_bit(key->bit_nr, &key->page->flags))
- return -1;
- } else {
- if (test_bit(key->bit_nr, &key->page->flags))
- return -1;
- }
+ if (!trylock_page_bit_common(key->page, key->bit_nr, wait))
+ return -1;
/*
* Let the waiter know we have done the page flag
@@ -1126,14 +1129,6 @@
*/
};
-static inline int trylock_page_bit_common(struct page *page, int bit_nr,
- enum behavior behavior)
-{
- return behavior == EXCLUSIVE ?
- !test_and_set_bit(bit_nr, &page->flags) :
- !test_bit(bit_nr, &page->flags);
-}
-
static inline int wait_on_page_bit_common(wait_queue_head_t *q,
struct page *page, int bit_nr, int state, enum behavior behavior)
{
@@ -1170,7 +1165,7 @@
*/
spin_lock_irq(&q->lock);
SetPageWaiters(page);
- if (!trylock_page_bit_common(page, bit_nr, behavior))
+ if (!trylock_page_bit_common(page, bit_nr, wait))
__add_wait_queue_entry_tail(q, wait);
spin_unlock_irq(&q->lock);
next prev parent reply other threads:[~2020-07-24 15:24 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 6:32 [RFC PATCH] mm: silence soft lockups from unlock_page Michal Hocko
[not found] ` <FCC3EB2D-9F11-4E9E-88F4-40B2926B35CC@lca.pw>
2020-07-21 11:25 ` Michal Hocko
[not found] ` <664A07B6-DBCD-4520-84F1-241A4E7A339F@lca.pw>
2020-07-21 12:17 ` Michal Hocko
[not found] ` <20200721132343.GA4261@lca.pw>
2020-07-21 13:38 ` Michal Hocko
2020-07-21 14:17 ` Chris Down
2020-07-21 15:00 ` Michal Hocko
2020-07-21 15:33 ` Linus Torvalds
2020-07-21 15:49 ` Michal Hocko
2020-07-22 18:29 ` Linus Torvalds
2020-07-22 21:29 ` Hugh Dickins
2020-07-22 22:10 ` Linus Torvalds
2020-07-22 23:42 ` Linus Torvalds
2020-07-23 0:23 ` Linus Torvalds
2020-07-23 12:47 ` Oleg Nesterov
2020-07-23 17:32 ` Linus Torvalds
2020-07-23 18:01 ` Oleg Nesterov
2020-07-23 18:22 ` Linus Torvalds
2020-07-23 19:03 ` Linus Torvalds
2020-07-24 14:45 ` Oleg Nesterov
2020-07-23 20:03 ` Linus Torvalds
2020-07-23 23:11 ` Hugh Dickins
2020-07-23 23:43 ` Linus Torvalds
2020-07-24 0:07 ` Hugh Dickins
2020-07-24 0:46 ` Linus Torvalds
2020-07-24 3:45 ` Hugh Dickins
2020-07-24 15:24 ` Oleg Nesterov [this message]
2020-07-24 17:32 ` Linus Torvalds
2020-07-24 23:25 ` Linus Torvalds
2020-07-25 2:08 ` Hugh Dickins
2020-07-25 2:46 ` Linus Torvalds
2020-07-25 10:14 ` Oleg Nesterov
2020-07-25 18:48 ` Linus Torvalds
2020-07-25 19:27 ` Oleg Nesterov
2020-07-25 19:51 ` Linus Torvalds
2020-07-26 13:57 ` Oleg Nesterov
2020-07-25 21:19 ` Hugh Dickins
2020-07-26 4:22 ` Hugh Dickins
2020-07-26 20:30 ` Hugh Dickins
2020-07-26 20:41 ` Linus Torvalds
2020-07-26 22:09 ` Hugh Dickins
2020-07-27 19:35 ` Greg KH
2020-08-06 5:46 ` Hugh Dickins
2020-08-18 13:50 ` Greg KH
2020-08-06 5:21 ` Hugh Dickins
2020-08-06 17:07 ` Linus Torvalds
2020-08-06 18:00 ` Matthew Wilcox
2020-08-06 18:32 ` Linus Torvalds
2020-08-07 18:41 ` Hugh Dickins
2020-08-07 19:07 ` Linus Torvalds
2020-08-07 19:35 ` Matthew Wilcox
2020-08-03 13:14 ` Michal Hocko
2020-08-03 17:56 ` Linus Torvalds
2020-07-25 9:39 ` Oleg Nesterov
2020-07-23 8:03 ` Michal Hocko
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