Date: Tue, 17 Dec 2002 00:27:06 +0100 (MET)
From: Mikael Pettersson <mikpe@csd.uu.se>
Message-Id: <200212162327.AAA06228@harpo.it.uu.se>
To: alan@lxorguk.ukuu.org.uk
Subject: Re: 2.4.21-pre1 broke the ide-tape driver
Cc: linux-kernel@vger.kernel.org, marcelo@conectiva.com.br
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2130
Lines: 55

I wrote:
>On Sun, 15 Dec 2002 02:23:34 +0100, Marc-Christian Petersen wrote:
>>> Kernel 2.4.21-pre1 broke the ide-tape driver: the driver
>>> now hangs during initialisation. 2.2 kernels (with Andre's
>>> IDE patch) and 2.4 up to 2.4.20 do not have this problem.
>>> My box has a Seagate STT8000A ATAPI tape drive as hdd;
>>> hdc is a Philips CD-RW, and the controller is ICH2 (i850 chipset).
>>http://linux.bkbits.net:8080/linux-2.4/patch@1.828?nav=index.html|ChangeSet@-7d|cset@1.828
>
>Addendum: this patch fixes the init-time hang, and ide-tape does
>seem to work fine, but 'rmmod ide-tape' oopses -- 2.4.20-ac2 also
>oopses on 'rmmod ide-tape'.

Solved, I think. Observe ide-tape's module_exit() procedure idetape_exit():

>static void __exit idetape_exit (void)
>{
>	ide_drive_t *drive;
>	int minor;
>
>	for (minor = 0; minor < MAX_HWIFS * MAX_DRIVES; minor++) {
>		drive = idetape_chrdevs[minor].drive;
>		if (drive != NULL && idetape_cleanup(drive))
>			printk(KERN_ERR "ide-tape: %s: cleanup_module() "
>				"called while still busy\n", drive->name);
>	}
>#ifdef CONFIG_PROC_FS
>	if (drive->proc)
>		ide_remove_proc_entries(drive->proc, idetape_proc);
>#endif
>
>	ide_unregister_module(&idetape_module);
>}

In the "if (drive->proc)" line, drive==NULL when I rmmod ide-tape,
causing the oops.

I'm not sure if ide_remove_proc_entries() is needed or not,
but the current code is obviously broken.

- ide_unregister_module() removes ide-tape's proc entry
  (/proc/ide/ideX/hdY/name) for us, at least that's what happens
  on my box after I commented out the entire "if (drive->proc) ..."
  statement to prevent the oops. So possibly the call should be deleted.

- ide-disk/ide-floppy do the test&call inside the loop rather than after,
  so possibly the call should be moved into the loop, and augmented
  to be "if (drive && drive->proc) ide_remove_proc_entries(...)".

/Mikael
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