From: Jan Kara <jack@suse.cz>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Amir Goldstein <amir73il@gmail.com>,
Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Jan Kara <jack@suse.cz>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: DEBUG_RWSEMS warning from thaw_super()
Date: Mon, 14 May 2018 11:50:22 +0200 [thread overview]
Message-ID: <20180514095022.nfp7vuepz4kfshni@quack2.suse.cz> (raw)
In-Reply-To: <20180513160404.GA19620@redhat.com>
On Sun 13-05-18 18:04:04, Oleg Nesterov wrote:
> On 05/13, Amir Goldstein wrote:
> >
> > Since kernel v4.17-rc1 and DEBUG_RWSEMS, I see the
> > warning below after filesystem freeze/thaw.
> >
> > This is a case where one process acquires a bunch of rwsem
> > and another process releases them.
> >
> > To convey this use case to lockdep, freeze_super() calls
> > lockdep_sb_freeze_release() on exit and thaw_super()
> > calls lockdep_sb_freeze_acquire() on entry.
>
> This was already discussed, but I forgot the result...
>
> So once again, why we can't simply update percpu_rwsem_acquire() ?
> Or we can check CONFIG_RWSEM_SPIN_ON_OWNER to match percpu_rwsem_release(),
> but CONFIG_DEBUG_RWSEMS explains the purpose better.
Yeah, what you suggests seems reasonable to me. So feel free to add:
Acked-by: Jan Kara <jack@suse.cz>
Honza
> --- x/include/linux/percpu-rwsem.h
> +++ x/include/linux/percpu-rwsem.h
> @@ -141,6 +141,10 @@ static inline void percpu_rwsem_acquire(
> bool read, unsigned long ip)
> {
> lock_acquire(&sem->rw_sem.dep_map, 0, 1, read, 1, NULL, ip);
> +#ifdef CONFIG_DEBUG_RWSEMS
> + if (!read)
> + sem->rw_sem.owner = current;
> +#endif
> }
>
> #endif
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2018-05-14 9:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-13 14:02 DEBUG_RWSEMS warning from thaw_super() Amir Goldstein
2018-05-13 16:04 ` Oleg Nesterov
2018-05-14 9:50 ` Jan Kara [this message]
2018-05-14 11:32 ` Amir Goldstein
2018-05-14 11:51 ` Oleg Nesterov
2018-05-14 12:16 ` Amir Goldstein
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