Re: [tip:locking/core] locking/lockdep/selftests: Add mixed read-write ABBA tests

Re: [tip:locking/core] locking/lockdep/selftests: Add mixed read-write ABBA tests

[Peter Zijlstra]

On Fri, Aug 25, 2017 at 04:55:48AM -0700, tip-bot for Peter Zijlstra wrote:
> Commit-ID:  e91498589746065e3ae95d9a00b068e525eec34f
> Gitweb:     http://git.kernel.org/tip/e91498589746065e3ae95d9a00b068e525eec34f
> Author:     Peter Zijlstra <peterz@infradead.org>
> AuthorDate: Wed, 23 Aug 2017 13:13:11 +0200
> Committer:  Ingo Molnar <mingo@kernel.org>
> CommitDate: Fri, 25 Aug 2017 11:06:31 +0200
> 
> locking/lockdep/selftests: Add mixed read-write ABBA tests
> 
> Currently lockdep has limited support for recursive readers, add a few
> mixed read-write ABBA selftests to show the extend of these
> limitations.
> 
>   [    0.000000] ----------------------------------------------------------------------------
>   [    0.000000]                                  | spin |wlock |rlock |mutex | wsem | rsem |
>   [    0.000000]   --------------------------------------------------------------------------
> 
>   [    0.000000]   mixed read-lock/lock-write ABBA:             |FAILED|             |  ok  |
>   [    0.000000]    mixed read-lock/lock-read ABBA:             |  ok  |             |  ok  |
>   [    0.000000]  mixed write-lock/lock-write ABBA:             |  ok  |             |  ok  |
> 
> This clearly illustrates the case where lockdep fails to find a
> deadlock.
> 

I'm an idiot...  this patch kills lockdep.

We want something like so on top.

---
 lib/locking-selftest.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 3c7151a6cd98..cd0b5c964bd0 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -2031,6 +2031,12 @@ void locking_selftest(void)
 	print_testname("mixed read-lock/lock-write ABBA");
 	pr_cont("             |");
 	dotest(rlock_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
+	/*
+	 * Lockdep does indeed fail here, but there's nothing we can do about
+	 * that now.  Don't kill lockdep for it.
+	 */
+	unexpected_testcase_failures--;
+
 	pr_cont("             |");
 	dotest(rwsem_ABBA1, FAILURE, LOCKTYPE_RWSEM);
 

[tip:locking/core] locking/lockdep/selftests: Fix mixed read-write ABBA tests

[tip-bot for Peter Zijlstra]

Commit-ID:  d82fed75294229abc9d757f08a4817febae6c4f4
Gitweb:     http://git.kernel.org/tip/d82fed75294229abc9d757f08a4817febae6c4f4
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 28 Aug 2017 14:42:45 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 29 Aug 2017 15:15:17 +0200

locking/lockdep/selftests: Fix mixed read-write ABBA tests

Commit:

  e91498589746 ("locking/lockdep/selftests: Add mixed read-write ABBA tests")

adds an explicit FAILURE to the locking selftest but overlooked the
fact that this kills lockdep. Fudge the test to avoid this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/20170828124245.xlo2yshxq2btgmuf@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 lib/locking-selftest.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 3c7151a..cd0b5c9 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -2031,6 +2031,12 @@ void locking_selftest(void)
 	print_testname("mixed read-lock/lock-write ABBA");
 	pr_cont("             |");
 	dotest(rlock_ABBA1, FAILURE, LOCKTYPE_RWLOCK);
+	/*
+	 * Lockdep does indeed fail here, but there's nothing we can do about
+	 * that now.  Don't kill lockdep for it.
+	 */
+	unexpected_testcase_failures--;
+
 	pr_cont("             |");
 	dotest(rwsem_ABBA1, FAILURE, LOCKTYPE_RWSEM);