linux-kernel - [PATCH v4 24/24] dept: Disable Dept on that map once it's been handled until next turn

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Date:   Fri,  4 Mar 2022 16:06:43 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     torvalds@...ux-foundation.org
Cc:     damien.lemoal@...nsource.wdc.com, linux-ide@...r.kernel.org,
        adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
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Subject: [PATCH v4 24/24] dept: Disable Dept on that map once it's been handled until next turn

Dept works with waits preceeding an event, that might lead a deadlock.
Once the event has been handled, it's hard to ensure further waits
actually contibute to deadlock until next turn, which will start when
a sleep associated with that map happens.

So let Dept start tracking dependency when a sleep happens and stop
tracking dependency once the event e.i. wake up, has been handled.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/dependency/dept.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c
index cc1b3a3..1c91db8 100644
--- a/kernel/dependency/dept.c
+++ b/kernel/dependency/dept.c
@@ -2325,6 +2325,12 @@ void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip,
 		do_event((void *)m, c, READ_ONCE(m->wgen), ip);
 		pop_ecxt((void *)m);
 	}
+
+	/*
+	 * Keep the map diabled until the next sleep.
+	 */
+	WRITE_ONCE(m->wgen, 0);
+
 	dept_exit(flags);
 }
 EXPORT_SYMBOL_GPL(dept_event);
@@ -2447,6 +2453,11 @@ void dept_event_split_map(struct dept_map_each *me,
 		pop_ecxt((void *)me);
 	}
 
+	/*
+	 * Keep the map diabled until the next sleep.
+	 */
+	WRITE_ONCE(me->wgen, 0);
+
 	dept_exit(flags);
 }
 EXPORT_SYMBOL_GPL(dept_event_split_map);
-- 
1.9.1