From: Jann Horn <jannh@google.com>
To: David Howells <dhowells@redhat.com>,
John Stultz <john.stultz@linaro.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
raven@themaw.net, Miklos Szeredi <mszeredi@redhat.com>,
Christian Brauner <christian@brauner.io>,
Linux API <linux-api@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
kernel list <linux-kernel@vger.kernel.org>
Subject: seq_lock and lockdep_is_held() assertions
Date: Fri, 21 Feb 2020 18:36:26 +0100 [thread overview]
Message-ID: <CAG48ez14CHMjZS8vCp6h6FnLvcFQq8oy_9JPCd=5qZ52X6w12Q@mail.gmail.com> (raw)
In-Reply-To: <2113718.1582304782@warthog.procyon.org.uk>
adding some locking folks to the thread...
On Fri, Feb 21, 2020 at 6:06 PM David Howells <dhowells@redhat.com> wrote:
> Jann Horn <jannh@google.com> wrote:
> > On Fri, Feb 21, 2020 at 1:24 PM David Howells <dhowells@redhat.com> wrote:
> > > What's the best way to write a lockdep assertion?
> > >
> > > BUG_ON(!lockdep_is_held(lock));
> >
> > lockdep_assert_held(lock) is the normal way, I think - that will
> > WARN() if lockdep is enabled and the lock is not held.
>
> Okay. But what's the best way with a seqlock_t? It has two dep maps in it.
> Do I just ignore the one attached to the spinlock?
Uuuh... very good question. Looking at how the seqlock_t helpers use
the dep map of the seqlock, I don't think lockdep asserts work for
asserting that you're in the read side of a seqlock?
read_seqbegin_or_lock() -> read_seqbegin() -> read_seqcount_begin() ->
seqcount_lockdep_reader_access() does seqcount_acquire_read() (which
maps to lock_acquire_shared_recursive()), but immediately following
that calls seqcount_release() (which maps to lock_release())?
So I think lockdep won't consider you to be holding any locks after
read_seqbegin_or_lock() if the lock wasn't taken?
next prev parent reply other threads:[~2020-02-21 17:36 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-18 17:04 [PATCH 00/19] VFS: Filesystem information and notifications [ver #16] David Howells
2020-02-18 17:05 ` [PATCH 01/19] vfs: syscall: Add fsinfo() to query filesystem information " David Howells
2020-02-19 16:31 ` Darrick J. Wong
2020-02-19 20:07 ` Jann Horn
2020-02-20 10:34 ` David Howells
2020-02-20 15:48 ` Darrick J. Wong
2020-02-20 11:03 ` David Howells
2020-02-20 14:54 ` Jann Horn
2020-02-20 15:31 ` Darrick J. Wong
2020-02-18 17:05 ` [PATCH 02/19] fsinfo: Add syscalls to other arches " David Howells
2020-02-21 14:51 ` Christian Brauner
2020-02-21 18:10 ` Geert Uytterhoeven
2020-02-18 17:05 ` [PATCH 03/19] fsinfo: Provide a bitmap of supported features " David Howells
2020-02-19 16:37 ` Darrick J. Wong
2020-02-20 12:22 ` David Howells
2020-02-18 17:05 ` [PATCH 04/19] vfs: Add mount change counter " David Howells
2020-02-21 14:48 ` Christian Brauner
2020-02-18 17:05 ` [PATCH 05/19] vfs: Introduce a non-repeating system-unique superblock ID " David Howells
2020-02-19 16:53 ` Darrick J. Wong
2020-02-20 12:45 ` David Howells
2020-02-18 17:05 ` [PATCH 06/19] vfs: Allow fsinfo() to look up a mount object by " David Howells
2020-02-21 15:09 ` Christian Brauner
2020-02-18 17:05 ` [PATCH 07/19] vfs: Allow mount information to be queried by fsinfo() " David Howells
2020-02-18 17:05 ` [PATCH 08/19] vfs: fsinfo sample: Mount listing program " David Howells
2020-02-18 17:06 ` [PATCH 09/19] fsinfo: Allow the mount topology propogation flags to be retrieved " David Howells
2020-02-18 17:06 ` [PATCH 10/19] fsinfo: Add API documentation " David Howells
2020-02-18 17:06 ` [PATCH 11/19] afs: Support fsinfo() " David Howells
2020-02-19 21:01 ` Jann Horn
2020-02-20 12:58 ` David Howells
2020-02-20 14:58 ` Jann Horn
2020-02-21 13:26 ` David Howells
2020-02-18 17:06 ` [PATCH 12/19] security: Add hooks to rule on setting a superblock or mount watch " David Howells
2020-02-18 17:06 ` [PATCH 13/19] vfs: Add a mount-notification facility " David Howells
2020-02-19 22:40 ` Jann Horn
2020-02-19 22:55 ` Jann Horn
2020-02-21 12:24 ` David Howells
2020-02-21 15:49 ` Jann Horn
2020-02-21 17:06 ` David Howells
2020-02-21 17:36 ` Jann Horn [this message]
2020-02-21 18:02 ` seq_lock and lockdep_is_held() assertions John Stultz
2020-02-18 17:06 ` [PATCH 14/19] notifications: sample: Display mount tree change notifications [ver #16] David Howells
2020-02-18 17:06 ` [PATCH 15/19] vfs: Add superblock " David Howells
2020-02-19 23:08 ` Jann Horn
2020-02-21 14:23 ` David Howells
2020-02-21 15:44 ` Jann Horn
2020-02-21 16:33 ` David Howells
2020-02-21 16:41 ` Jann Horn
2020-02-21 17:11 ` David Howells
2020-02-18 17:06 ` [PATCH 16/19] fsinfo: Provide superblock notification counter " David Howells
2020-02-18 17:07 ` [PATCH 17/19] notifications: sample: Display superblock notifications " David Howells
2020-02-18 17:07 ` [PATCH 18/19] ext4: Add example fsinfo information " David Howells
2020-02-19 17:04 ` Darrick J. Wong
2020-02-20 0:53 ` kbuild test robot
2020-02-21 14:43 ` David Howells
2020-02-21 16:26 ` Darrick J. Wong
2020-02-18 17:07 ` [PATCH 19/19] nfs: Add example filesystem " David Howells
2020-02-20 2:13 ` kbuild test robot
2020-02-20 2:20 ` kbuild test robot
2020-02-18 18:12 ` David Howells
2020-02-19 10:23 ` [PATCH 00/19] VFS: Filesystem information and notifications " Stefan Metzmacher
2020-02-19 14:46 ` Christian Brauner
2020-02-19 15:50 ` Darrick J. Wong
2020-02-20 4:42 ` Ian Kent
2020-02-20 9:09 ` Christian Brauner
2020-02-20 11:30 ` Ian Kent
2020-02-19 16:16 ` David Howells
2020-02-21 12:57 ` David Howells
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