From: Bart Van Assche <bvanassche@acm.org>
To: Miklos Szeredi <miklos@szeredi.hu>, Christoph Hellwig <hch@lst.de>
Cc: 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: Tue, 05 Feb 2019 16:53:04 -0800 [thread overview]
Message-ID: <1549414384.34241.77.camel@acm.org> (raw)
In-Reply-To: <CAJfpegtkPSss5LxB3eEK7tLCu+tv5GOeM+Wu+cksUxjvSg3now@mail.gmail.com>
On Tue, 2019-02-05 at 09:12 +0100, Miklos Szeredi wrote:
> Not all variants of the waitqueue interface require irqs to be
> disabled, and fuse has nothing whatsoever to do with irqs, so there's
> no sane reason to disable them.
>
> Also, AFAICS, the fuse device does not support asynchronous IO. I
> just don't get what this is about...
Hi Miklos,
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).
Thanks,
Bart.
next prev parent reply other threads:[~2019-02-06 0:53 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 [this message]
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
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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