linux-kernel - Re: [PATCH] pci: iov: use device lock to protect IOV sysfs accesses

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Message-ID: <20170523052546.GA1408@infradead.org>
Date:   Mon, 22 May 2017 22:25:46 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Emil Tantilov <emil.s.tantilov@...el.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH] pci: iov: use device lock to protect IOV sysfs accesses

On Mon, May 22, 2017 at 03:50:23PM -0700, Jakub Kicinski wrote:
> PCI core sets the driver pointer before calling ->probe() and only
> clears it after ->remove().  This means driver's ->sriov_configure()
> callback will happily race with probe() and remove(), most likely
> leading to BUGs, since drivers don't expect this.
> 
> We could reorder pointer assignments, or try detecting races in all
> drivers, but it seems simpler and cleaner to just hold the device lock
> instead of special SR-IOV lock, since that lock is already supposed
> to synchronize the driver callbacks.
> 
> Remove the iov lock completely, since we remove the last user.

Having just debugged a different method vs ->remove race I violently
agree.

Reviewed-by: Christoph Hellwig <hch@....de>