linux-kernel - [PATCH 4.17 126/220] locking/rwsem: Fix up_read_non_owner() warning with DEBUG

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Message-Id: <20180701160913.605670833@linuxfoundation.org>
Date:   Sun,  1 Jul 2018 18:22:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Waiman Long <longman@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Gavin Schenk <g.schenk@...elmann.de>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dan Williams <dan.j.williams@...el.com>,
        Arnd Bergmann <arnd@...db.de>, linux-nfs@...r.kernel.org
Subject: [PATCH 4.17 126/220] locking/rwsem: Fix up_read_non_owner() warning with DEBUG_RWSEMS

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Waiman Long <longman@...hat.com>

commit 03eeafdd9ab06a770d42c2b264d50dff7e2f4eee upstream.

It was found that the use of up_read_non_owner() in NFS was causing
the following warning when DEBUG_RWSEMS was configured.

  DEBUG_LOCKS_WARN_ON(sem->owner != ((struct task_struct *)(1UL << 0)))

Looking into the rwsem.c file, it was discovered that the corresponding
down_read_non_owner() function was not setting the owner field properly.
This is fixed now, and the warning should be gone.

Fixes: 5149cbac4235 ("locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches")
Signed-off-by: Waiman Long <longman@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Gavin Schenk <g.schenk@...elmann.de>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: linux-nfs@...r.kernel.org
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/1527168398-4291-1-git-send-email-longman@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/locking/rwsem.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -181,6 +181,7 @@ void down_read_non_owner(struct rw_semap
 	might_sleep();
 
 	__down_read(sem);
+	rwsem_set_reader_owned(sem);
 }
 
 EXPORT_SYMBOL(down_read_non_owner);