From: Heiko Carstens <hca@linux.ibm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Nathan Chancellor <nathan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
gor@linux.ibm.com, Alexander Gordeev <agordeev@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
wintera@linux.ibm.com, twinkler@linux.ibm.com,
linux-s390@vger.kernel.org, Netdev <netdev@vger.kernel.org>,
llvm@lists.linux.dev, patches@lists.linux.dev
Subject: Re: [PATCH 1/3] s390/vmlogrdr: Remove function pointer cast
Date: Mon, 6 May 2024 21:26:02 +0200 [thread overview]
Message-ID: <20240506192602.19333-A-hca@linux.ibm.com> (raw)
In-Reply-To: <798df2d7-b13f-482a-8d4a-106c6492af01@app.fastmail.com>
On Thu, Apr 18, 2024 at 09:46:18PM +0200, Arnd Bergmann wrote:
> On Thu, Apr 18, 2024, at 17:15, Heiko Carstens wrote:
> > That doesn't answer my question what prevents the release function
> > from being called after the module has been unloaded.
> >
> > At least back then when the code was added it was a real bug.
>
> I think the way this should work is to have the allocation and
> the release function in the iucv bus driver, with a function
> roughly like
>
> struct device *iucv_alloc_device(char *name,
> const struct attribute_group *attrs,
> void *priv)
> {
> dev = kzalloc(sizeof(struct device), GFP_KERNEL);
> if (!dev)
> return NULL;
>
> dev_set_name(dev, "%s", name);
> dev->bus = &iucv_bus;
> dev->parent = iucv_root;
> dev->groups = attrs;
> dev_set_drvdata(dev, priv);
> dev->release = iucv_free_dev;
>
> return dev;
> }
>
> Now the release function cannot go away as long as any module
> is loaded that links against it, and those modules cannot
> go away as long as the devices are in use.
>
> I don't remember how iucv works, but if there is a way to
> detect which system services exist, then the actual device
> creation should also be separate from the driver using those
> services, with another driver responsible for enumerating
> the existing services and creating those devices.
So, I finally had a deeper look at this, and it looks like the comment
that says that the release function can be called after the module is
unloaded is not correct (anymore?).
I couldn't find any put_device() calls where not also the module reference
count is increased. So I guess Nathan's patches are just fine.
However given your above suggestion, I implemented an iucv_alloc_device()
function to get rid of quite some code duplication, and the casts as well.
I'll send the series for review.
next prev parent reply other threads:[~2024-05-06 19:26 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-17 18:24 [PATCH 0/3] drivers/s390: Fix instances of -Wcast-function-type-strict Nathan Chancellor
2024-04-17 18:24 ` [PATCH 1/3] s390/vmlogrdr: Remove function pointer cast Nathan Chancellor
2024-04-17 18:55 ` Arnd Bergmann
2024-04-18 5:56 ` Thomas Huth
2024-04-18 9:54 ` Heiko Carstens
2024-04-18 10:25 ` Heiko Carstens
2024-04-18 14:51 ` Nathan Chancellor
2024-04-18 15:15 ` Heiko Carstens
2024-04-18 15:34 ` Nathan Chancellor
2024-04-18 19:21 ` Heiko Carstens
2024-04-18 20:32 ` Nathan Chancellor
2024-04-18 19:46 ` Arnd Bergmann
2024-04-19 12:15 ` Heiko Carstens
2024-04-19 12:19 ` Arnd Bergmann
2024-04-19 14:12 ` Heiko Carstens
2024-04-23 7:34 ` Alexandra Winter
2024-05-06 19:26 ` Heiko Carstens [this message]
2024-04-17 18:24 ` [PATCH 2/3] s390/smsgiucv_app: " Nathan Chancellor
2024-04-17 18:56 ` Arnd Bergmann
2024-04-18 5:56 ` Thomas Huth
2024-04-17 18:24 ` [PATCH 3/3] s390/netiucv: " Nathan Chancellor
2024-04-17 18:57 ` Arnd Bergmann
2024-04-18 5:57 ` Thomas Huth
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