From: Christoph Hellwig <hch@lst.de>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
Christoph Hellwig <hch@lst.de>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, linux-aio <linux-aio@kvack.org>,
syzbot <syzkaller@googlegroups.com>,
Avi Kivity <avi@scylladb.com>, Eric Dumazet <edumazet@google.com>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] aio: Fix locking in aio_poll()
Date: Wed, 6 Feb 2019 14:39:35 +0100 [thread overview]
Message-ID: <20190206133935.GA29185@lst.de> (raw)
In-Reply-To: <1549414384.34241.77.camel@acm.org>
On Tue, Feb 05, 2019 at 04:53:04PM -0800, Bart Van Assche wrote:
> Could this be what happens?
>
> aio_poll() calls vfs_poll()
> vfs_poll() calls fuse_dev_poll()
> fuse_dev_poll() calls poll_wait(file, &fiq->waitq, wait)
> poll_wait() calls aio_poll_queue_proc(file, &fiq->waitq, wait)
> aio_poll_queue_proc() stores &fiq->waitq in pt->iocb->poll.head
> aio_poll() calls spin_lock_irq(&ctx->ctx_lock)
> aio_poll() calls spin_lock(&req->head->lock) (req == &pt->iocb->poll).
>
> I think the lockdep complaint is about the FUSE fiq->waitq lock not being
> IRQ-safe and about aio_poll() creating a dependency between an IRQ-safe lock
> (ctx->ctx_lock) and a lock that is not IRQ-safe (fiq->waitq).
That is exactly the scenario. and the ->wake routine assumes irqs
are disabled - you really need to bypass the proper APIs to not have
the irqs disabled.
next prev parent reply other threads:[~2019-02-06 13:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-04 17:45 [PATCH] aio: Fix locking in aio_poll() Bart Van Assche
2019-02-04 17:49 ` Christoph Hellwig
2019-02-05 8:12 ` Miklos Szeredi
2019-02-06 0:53 ` Bart Van Assche
2019-02-06 8:36 ` Miklos Szeredi
2019-02-06 13:47 ` Christoph Hellwig
2019-02-06 14:31 ` Miklos Szeredi
2019-02-06 13:39 ` Christoph Hellwig [this message]
2019-02-09 0:59 Bart Van Assche
2019-02-12 7:56 ` Christoph Hellwig
2019-02-21 22:28 ` Bart Van Assche
2019-02-22 3:17 ` Al Viro
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