2.6.0-test6 module autoloading and reference counting broken?

2.6.0-test6 module autoloading and reference counting broken?

[Mikael Pettersson]

FYI,

I'm seeing incorrect reference counting behaviour and module
loading semi-failures in 2.6.0-test6.

I have a misc char driver module which announces an alias
via a MODULE_ALIAS("char-major-10-<nnn>") declaration.

The first attempt by user-space to open the device node fails
with ENODEV. However, afterwards the module _is_ loaded and its
use count is 1 even though the user-space open() failed.

Subsequent open()s succeed, but since the reference count is
one too high, I can't unload the module.

If I instead manually insmod or modprobe the module before the
first device node open(), the module's use count is correct and
I can unload it after the last open()ed file goes away.

CONFIG_KMOD is set, module-init-tools is 0.9.14.

I'll keep digging...

/Mikael

Re: 2.6.0-test6 module autoloading and reference counting broken?

[Rusty Russell]

In message <16253.27644.578089.345998@gargle.gargle.HOWL> you write:
> FYI,
> 
> I'm seeing incorrect reference counting behaviour and module
> loading semi-failures in 2.6.0-test6.
> 
> I have a misc char driver module which announces an alias
> via a MODULE_ALIAS("char-major-10-<nnn>") declaration.
> 
> The first attempt by user-space to open the device node fails
> with ENODEV. However, afterwards the module _is_ loaded and its
> use count is 1 even though the user-space open() failed.

Sounds like a refcount bug somewhere (in your module, maybe?).
There's nothing magic about modules loaded via kmod, even via
aliases, unless there's a bug in drivers/char/misc.c...

Puzzled,
Rusty.
--
  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.

Re: 2.6.0-test6 module autoloading and reference counting broken?

[Mikael Pettersson]

On Fri, 10 Oct 2003 15:25:20 +1000, Rusty Russell wrote:
>In message <16253.27644.578089.345998@gargle.gargle.HOWL> you write:
>> FYI,
>> 
>> I'm seeing incorrect reference counting behaviour and module
>> loading semi-failures in 2.6.0-test6.
>> 
>> I have a misc char driver module which announces an alias
>> via a MODULE_ALIAS("char-major-10-<nnn>") declaration.
>> 
>> The first attempt by user-space to open the device node fails
>> with ENODEV. However, afterwards the module _is_ loaded and its
>> use count is 1 even though the user-space open() failed.
>
>Sounds like a refcount bug somewhere (in your module, maybe?).
>There's nothing magic about modules loaded via kmod, even via
>aliases, unless there's a bug in drivers/char/misc.c...

test6 did introduce a bug in drivers/char/misc.c causing
the problems I described. It's been fixed in test7.

/Mikael