From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-mm@kvack.org
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@suse.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save().
Date: Wed, 21 Jun 2023 12:40:34 +0200 [thread overview]
Message-ID: <20230621104034.HT6QnNkQ@linutronix.de> (raw)
__build_all_zonelists() acquires zonelist_update_seq by first disabling
interrupts via local_irq_save() and then acquiring the seqlock with
write_seqlock(). This is troublesome and leads to problems on
PREEMPT_RT because the inner spinlock_t is now acquired with disabled
interrupts.
The API provides write_seqlock_irqsave() which does the right thing in
one step.
printk_deferred_enter() has to be invoked in non-migrate-able context to
ensure that deferred printing is enabled and disabled on the same CPU.
This is the case after zonelist_update_seq has been acquired.
Acquire zonelist_update_seq with write_seqlock_irqsave() and then defer
printk output.
Fixes: 1007843a91909 ("mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
mm/page_alloc.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 47421bedc12b7..99b7e7d09c5c0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5808,11 +5808,10 @@ static void __build_all_zonelists(void *data)
unsigned long flags;
/*
- * Explicitly disable this CPU's interrupts before taking seqlock
- * to prevent any IRQ handler from calling into the page allocator
- * (e.g. GFP_ATOMIC) that could hit zonelist_iter_begin and livelock.
+ * The zonelist_update_seq must be acquired with irqsave because the
+ * reader can be invoked from IRQ with GFP_ATOMIC.
*/
- local_irq_save(flags);
+ write_seqlock_irqsave(&zonelist_update_seq, flags);
/*
* Explicitly disable this CPU's synchronous printk() before taking
* seqlock to prevent any printk() from trying to hold port->lock, for
@@ -5820,7 +5819,6 @@ static void __build_all_zonelists(void *data)
* calling kmalloc(GFP_ATOMIC | __GFP_NOWARN) with port->lock held.
*/
printk_deferred_enter();
- write_seqlock(&zonelist_update_seq);
#ifdef CONFIG_NUMA
memset(node_load, 0, sizeof(node_load));
@@ -5857,9 +5855,8 @@ static void __build_all_zonelists(void *data)
#endif
}
- write_sequnlock(&zonelist_update_seq);
printk_deferred_exit();
- local_irq_restore(flags);
+ write_sequnlock_irqrestore(&zonelist_update_seq, flags);
}
static noinline void __init
--
2.40.1
next reply other threads:[~2023-06-21 10:40 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-21 10:40 Sebastian Andrzej Siewior [this message]
2023-06-21 10:59 ` [PATCH] mm/page_alloc: Use write_seqlock_irqsave() instead write_seqlock() + local_irq_save() Michal Hocko
2023-06-21 11:16 ` Sebastian Andrzej Siewior
2023-06-21 11:49 ` Michal Hocko
2023-06-21 13:11 ` Sebastian Andrzej Siewior
2023-06-21 13:22 ` Michal Hocko
2023-06-21 13:25 ` Sebastian Andrzej Siewior
2023-06-21 11:14 ` David Hildenbrand
2023-06-21 11:33 ` Tetsuo Handa
2023-06-21 12:40 ` Petr Mladek
2023-06-21 13:08 ` Sebastian Andrzej Siewior
2023-06-21 13:06 ` Sebastian Andrzej Siewior
2023-06-21 13:32 ` Tetsuo Handa
2023-06-21 14:34 ` Sebastian Andrzej Siewior
2023-06-21 14:50 ` Tetsuo Handa
2023-06-21 23:24 ` Tetsuo Handa
2023-06-22 7:18 ` Michal Hocko
2023-06-22 10:58 ` Tetsuo Handa
2023-06-22 12:09 ` Michal Hocko
2023-06-22 13:36 ` Tetsuo Handa
2023-06-22 14:11 ` Petr Mladek
2023-06-22 14:28 ` Tetsuo Handa
2023-06-23 9:35 ` Sebastian Andrzej Siewior
2023-06-22 15:04 ` Petr Mladek
2023-06-22 15:43 ` Tetsuo Handa
2023-06-23 9:45 ` Sebastian Andrzej Siewior
2023-06-23 9:51 ` Tetsuo Handa
2023-06-23 10:11 ` Sebastian Andrzej Siewior
2023-06-23 10:36 ` Tetsuo Handa
2023-06-23 12:44 ` Sebastian Andrzej Siewior
2023-06-23 12:57 ` Michal Hocko
2023-06-23 10:53 ` Petr Mladek
2023-06-23 11:16 ` Tetsuo Handa
2023-06-23 13:31 ` Sebastian Andrzej Siewior
2023-06-23 15:38 ` Petr Mladek
2023-06-23 16:04 ` Sebastian Andrzej Siewior
2023-06-23 9:31 ` Sebastian Andrzej Siewior
2023-06-23 7:27 ` Sebastian Andrzej Siewior
2023-06-21 15:38 ` Petr Mladek
2023-06-23 8:12 ` Sebastian Andrzej Siewior
2023-06-23 9:21 ` Michal Hocko
2023-06-23 9:58 ` Sebastian Andrzej Siewior
2023-06-23 10:43 ` Michal Hocko
2023-06-23 10:45 ` Sebastian Andrzej Siewior
2023-06-23 10:50 ` Sebastian Andrzej Siewior
2023-06-23 11:32 ` Michal Hocko
2023-06-23 10:40 ` Petr Mladek
2023-06-23 13:24 ` Sebastian Andrzej Siewior
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