linux-kernel - Re: [PATCH] pci/switchtec: fix stream

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Date:   Sat, 13 Apr 2019 17:01:00 +0000
From:   Kirill Smelkov <kirr@...edi.com>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        <kbuild-all@...org>, Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pci/switchtec: fix stream_open.cocci warnings (fwd)

Hello everyone,

On Sat, Apr 13, 2019 at 06:50:57PM +0200, Julia Lawall wrote:
> Hello,
> 
> Kirill will explain about this issue.

pci/switchtec switching to stream_open is already queued to merge
window and it was acked by Logan Gunthorpe:

        https://lore.kernel.org/lkml/CAHk-=wgqgN5j1ZWnyVLqqoyU=CCWTYOko3MDyU8L_5e21KvHAg@mail.gmail.com/
        https://lab.nexedi.com/kirr/linux/commit/edaeb4101860

( there are too many Cc's in that patch and email with it and reply-all to
  it did not get into mailing list probably due to being considered as spam )

stream_open.cocci was issuing only warning for pci/switchtec, but after
8a29a3bae2a2 ("pci/switchtec: Don't use completion's wait queue") they
started to use wait_even_* inside read method and, since
stream_open.cocci considers wait_event_* as blocking the warning became
error. Previously it was completions there, but I added support for wait
events only for simplicity.

I can handle pci/switchtec switching via big nonseekable_open ->
stream_open change at next merge window, or, alternatively please feel
free to switch pci/switchtec now on its own. The change is correct - I
was manually reviewing all changes that stream_open.cocci produces and
pci/switchtec was there.

Kirill

> julia
> 
> ---------- Forwarded message ----------
> Date: Sat, 13 Apr 2019 11:22:51 +0800
> From: kbuild test robot <lkp@...el.com>
> To: kbuild@...org
> Cc: Julia Lawall <julia.lawall@...6.fr>
> Subject: [PATCH] pci/switchtec: fix stream_open.cocci warnings
> 
> CC: kbuild-all@...org
> TO: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> CC: Kurt Schwemmer <kurt.schwemmer@...rosemi.com>
> CC: Logan Gunthorpe <logang@...tatee.com>
> CC: Bjorn Helgaas <helgaas@...nel.org>
> CC: linux-pci@...r.kernel.org
> CC: linux-kernel@...r.kernel.org
> 
> From: kbuild test robot <lkp@...el.com>
> 
> drivers/pci/switch/switchtec.c:395:1-17: ERROR: switchtec_fops: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix.
> 
> Generated by: scripts/coccinelle/api/stream_open.cocci
> 
> Fixes: 8a29a3bae2a2 ("pci/switchtec: Don't use completion's wait queue")
> Signed-off-by: kbuild test robot <lkp@...el.com>
> ---
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-5.0.y-rt-rebase
> head:   794c294ae4483c240429c25a0d18e272e92c94de
> commit: 8a29a3bae2a2dfb0116cd8791d9700515d6e765e [154/311] pci/switchtec: Don't use completion's wait queue
> :::::: branch date: 7 hours ago
> :::::: commit date: 7 hours ago
> 
> Please take the patch only if it's a positive warning. Thanks!
> 
>  switchtec.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/drivers/pci/switch/switchtec.c
> +++ b/drivers/pci/switch/switchtec.c
> @@ -392,7 +392,7 @@ static int switchtec_dev_open(struct ino
>  		return PTR_ERR(stuser);
> 
>  	filp->private_data = stuser;
> -	nonseekable_open(inode, filp);
> +	stream_open(inode, filp);
> 
>  	dev_dbg(&stdev->dev, "%s: %p\n", __func__, stuser);