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From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Andrea Parri <parri.andrea@gmail.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Boqun Feng <boqun.feng@gmail.com>
Subject: [RFC tip/locking/lockdep v6 13/20] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior
Date: Wed, 11 Apr 2018 21:51:03 +0800	[thread overview]
Message-ID: <20180411135110.9217-14-boqun.feng@gmail.com> (raw)
In-Reply-To: <20180411135110.9217-1-boqun.feng@gmail.com>

As our chain cache doesn't differ read/write locks, so even we can
detect a read-lock/lock-write deadlock in check_noncircular(), we can
still be fooled if a read-lock/lock-read case(which is not a deadlock)
comes first.

So introduce this test case to test specific to the chain cache behavior
on detecting recursive read lock related deadlocks.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 lib/locking-selftest.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index b5c1293ce147..700f9aa19db6 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -395,6 +395,49 @@ static void rwsem_ABBA1(void)
 	MU(Y1); // should fail
 }
 
+/*
+ * read_lock(A)
+ * spin_lock(B)
+ *		spin_lock(B)
+ *		write_lock(A)
+ *
+ * This test case is aimed at poking whether the chain cache prevents us from
+ * detecting a read-lock/lock-write deadlock: if the chain cache doesn't differ
+ * read/write locks, the following case may happen
+ *
+ * 	{ read_lock(A)->lock(B) dependency exists }
+ *
+ * 	P0:
+ * 	lock(B);
+ * 	read_lock(A);
+ *
+ *	{ Not a deadlock, B -> A is added in the chain cache }
+ *
+ *	P1:
+ *	lock(B);
+ *	write_lock(A);
+ *
+ *	{ B->A found in chain cache, not reported as a deadlock }
+ *
+ */
+static void rlock_chaincache_ABBA1(void)
+{
+	RL(X1);
+	L(Y1);
+	U(Y1);
+	RU(X1);
+
+	L(Y1);
+	RL(X1);
+	RU(X1);
+	U(Y1);
+
+	L(Y1);
+	WL(X1);
+	WU(X1);
+	U(Y1); // should fail
+}
+
 /*
  * read_lock(A)
  * spin_lock(B)
@@ -2055,6 +2098,10 @@ void locking_selftest(void)
 	pr_cont("             |");
 	dotest(rwsem_ABBA3, FAILURE, LOCKTYPE_RWSEM);
 
+	print_testname("chain cached mixed R-L/L-W ABBA");
+	pr_cont("             |");
+	dotest(rlock_chaincache_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
+
 	printk("  --------------------------------------------------------------------------\n");
 
 	/*
-- 
2.16.2

  parent reply	other threads:[~2018-04-11 13:48 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11 13:50 [RFC tip/locking/lockdep v6 00/20] lockdep: Support deadlock detection for recursive read locks Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 01/20] lockdep/Documention: Recursive read lock detection reasoning Boqun Feng
2018-04-15  0:38   ` Randy Dunlap
2018-04-16  6:29     ` Boqun Feng
2018-04-27 13:50   ` Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 02/20] lockdep: Demagic the return value of BFS Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 03/20] lockdep: Make __bfs() visit every dependency until a match Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 04/20] lockdep: Redefine LOCK_*_STATE* bits Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 05/20] lockdep: Reduce the size of lock_list::distance Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 06/20] lockdep: Introduce lock_list::dep Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 07/20] lockdep: Extend __bfs() to work with multiple types of dependencies Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 08/20] lockdep: Make __bfs(.match) return bool Boqun Feng
2018-04-11 13:50 ` [RFC tip/locking/lockdep v6 09/20] lockdep: Support deadlock detection for recursive read locks in check_noncircular() Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 10/20] lockdep: Adjust check_redundant() for recursive read change Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 11/20] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 12/20] lockdep: Add recursive read locks into dependency graph Boqun Feng
2018-04-11 13:51 ` Boqun Feng [this message]
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 14/20] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 15/20] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 16/20] lockdep/selftest: Add more recursive read related test cases Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 17/20] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng
2018-04-11 13:51 ` [RFC tip/locking/lockdep v6 18/20] MAINTAINERS: Add myself as a LOCKING PRIMITIVES reviewer Boqun Feng
2018-04-11 13:56 ` [RFC tip/locking/lockdep v6 19/20] rcu: Equip sleepable RCU with lockdep dependency graph checks Boqun Feng
2018-04-11 18:57   ` Paul E. McKenney
2018-04-12  2:12     ` Boqun Feng
2018-04-12  9:12       ` Peter Zijlstra
2018-04-13 13:24         ` Boqun Feng
2018-04-11 13:57 ` [RFC tip/locking/lockdep v6 20/20] lockdep/selftest: Add a test case for SRCU Boqun Feng

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