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From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: Will Deacon <will@kernel.org>, Eric Dumazet <edumazet@google.com>,
	Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
	Maddie Stone <maddiestone@google.com>,
	Marco Elver <elver@google.com>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	kernel-team@android.com, kernel-hardening@lists.openwall.com
Subject: [RFC PATCH 02/21] list: Remove hlist_nulls_unhashed_lockless()
Date: Tue, 24 Mar 2020 15:36:24 +0000	[thread overview]
Message-ID: <20200324153643.15527-3-will@kernel.org> (raw)
In-Reply-To: <20200324153643.15527-1-will@kernel.org>

Commit 02b99b38f3d9 ("rcu: Add a hlist_nulls_unhashed_lockless() function")
introduced the (as yet unused) hlist_nulls_unhashed_lockless() function
to avoid KCSAN reports when an RCU reader checks the 'hashed' status
of an 'hlist_nulls' concurrently undergoing modification.

Remove the unused function and add a READ_ONCE() to hlist_nulls_unhashed(),
just like we do already for hlist_nulls_empty().

Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
 include/linux/list_nulls.h | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index fa6e8471bd22..3a9ff01e9a11 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -65,20 +65,6 @@ static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr)
  * but hlist_nulls_del() does not.
  */
 static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
-{
-	return !h->pprev;
-}
-
-/**
- * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized?
- * @h: Node to be checked
- *
- * Not that not all removal functions will leave a node in unhashed state.
- * For example, hlist_del_init_rcu() leaves the node in unhashed state,
- * but hlist_nulls_del() does not.  Unlike hlist_nulls_unhashed(), this
- * function may be used locklessly.
- */
-static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h)
 {
 	return !READ_ONCE(h->pprev);
 }
-- 
2.20.1


  parent reply	other threads:[~2020-03-24 15:36 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-24 15:36 [RFC PATCH 00/21] Improve list integrity checking Will Deacon
2020-03-24 15:36 ` [RFC PATCH 01/21] list: Remove hlist_unhashed_lockless() Will Deacon
2020-03-24 16:27   ` Greg KH
2020-03-30 23:05   ` Paul E. McKenney
2020-03-24 15:36 ` Will Deacon [this message]
2020-03-24 16:27   ` [RFC PATCH 02/21] list: Remove hlist_nulls_unhashed_lockless() Greg KH
2020-03-30 23:07   ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 03/21] list: Annotate lockless list primitives with data_race() Will Deacon
2020-03-24 16:20   ` Jann Horn
2020-03-24 16:20     ` Jann Horn
2020-03-24 16:26     ` Greg KH
2020-03-24 16:38       ` Jann Horn
2020-03-24 16:38         ` Jann Horn
2020-03-24 16:59         ` Greg KH
2020-03-24 18:22           ` Jann Horn
2020-03-24 18:22             ` Jann Horn
2020-03-24 16:23   ` Marco Elver
2020-03-24 16:23     ` Marco Elver
2020-03-24 21:33     ` Will Deacon
2020-03-31 13:10     ` Will Deacon
2020-04-01  6:34       ` Marco Elver
2020-04-01  6:34         ` Marco Elver
2020-04-01  8:40         ` Will Deacon
2020-05-08 13:46       ` [tip: locking/kcsan] kcsan: Change data_race() to no longer require marking racing accesses tip-bot2 for Marco Elver
2020-03-24 16:51   ` [RFC PATCH 03/21] list: Annotate lockless list primitives with data_race() Peter Zijlstra
2020-03-24 16:56     ` Jann Horn
2020-03-24 16:56       ` Jann Horn
2020-03-24 21:32       ` Will Deacon
2020-03-30 23:13         ` Paul E. McKenney
2020-04-24 17:39           ` Will Deacon
2020-04-27 19:24             ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 04/21] timers: Use hlist_unhashed() instead of open-coding in timer_pending() Will Deacon
2020-03-24 16:30   ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 05/21] list: Comment missing WRITE_ONCE() in __list_del() Will Deacon
2020-03-30 23:14   ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 06/21] list: Remove superfluous WRITE_ONCE() from hlist_nulls implementation Will Deacon
2020-03-30 23:21   ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 07/21] Revert "list: Use WRITE_ONCE() when adding to lists and hlists" Will Deacon
2020-03-30 23:19   ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 08/21] Revert "list: Use WRITE_ONCE() when initializing list_head structures" Will Deacon
2020-03-30 23:25   ` Paul E. McKenney
2020-03-31 13:11     ` Will Deacon
2020-03-31 13:47       ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 09/21] list: Remove unnecessary WRITE_ONCE() from hlist_bl_add_before() Will Deacon
2020-03-30 23:30   ` Paul E. McKenney
2020-03-31 12:37     ` Will Deacon
2020-03-24 15:36 ` [RFC PATCH 10/21] kernel-hacking: Make DEBUG_{LIST,PLIST,SG,NOTIFIERS} non-debug options Will Deacon
2020-03-24 16:42   ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 11/21] list: Add integrity checking to hlist implementation Will Deacon
2020-03-24 15:36 ` [RFC PATCH 12/21] list: Poison ->next pointer for non-RCU deletion of 'hlist_nulls_node' Will Deacon
2020-03-30 23:32   ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 13/21] list: Add integrity checking to hlist_nulls implementation Will Deacon
2020-03-24 15:36 ` [RFC PATCH 14/21] plist: Use CHECK_DATA_CORRUPTION instead of explicit {BUG,WARN}_ON() Will Deacon
2020-03-24 16:42   ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 15/21] list_bl: Use CHECK_DATA_CORRUPTION instead of custom BUG_ON() wrapper Will Deacon
2020-03-24 15:36 ` [RFC PATCH 16/21] list_bl: Extend integrity checking in deletion routines Will Deacon
2020-03-24 15:36 ` [RFC PATCH 17/21] linux/bit_spinlock.h: Include linux/processor.h Will Deacon
2020-03-24 16:28   ` Greg KH
2020-03-24 21:08     ` Will Deacon
2020-03-24 15:36 ` [RFC PATCH 18/21] list_bl: Move integrity checking out of line Will Deacon
2020-03-24 15:36 ` [RFC PATCH 19/21] list_bl: Extend integrity checking to cover the same cases as 'hlist' Will Deacon
2020-03-24 15:36 ` [RFC PATCH 20/21] list: Format CHECK_DATA_CORRUPTION error messages consistently Will Deacon
2020-03-24 16:40   ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 21/21] lkdtm: Extend list corruption checks Will Deacon

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