lkml.org 
[lkml]   [2001]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectFwd: Claim serialization problem
Johannes,

the attached patch fixed a real problem for me and
the linux-usb-devel folks agreed it was a good fix.
Do you mind to push it to Linus? The 2.4.6 still
has no trace of it.

Thanks,
-- Pete

cc: to linux-kernel in case the maintainer is hit by a bus.

----- Forwarded message from Pete Zaitcev <zaitcev@redhat.com> -----

Date: Tue, 29 May 2001 23:07:58 -0400
From: Pete Zaitcev <zaitcev@redhat.com>
To: linux-usb-devel@lists.sourceforge.net
Cc: zaitcev@redhat.com
Subject: Claim serialization problem
User-Agent: Mutt/1.2.5i

Hi,

I attached a USB tape (Freecom based) to my machine and
the usb-storage driver registered itself 3 times with SCSI.
Upon a closer inspection the following was found, approximately:

usb_find_interface_driver () {
if (usb_interface_claimed(interface))
goto out_err;
down(&driver->serialize);
private = driver->probe(dev,ifnum,id);
up(&driver->serialize);
usb_driver_claim_interface(driver, interface, private);
}

This is wrong even on UP.

Here is a patch that fixes the problem for me:

diff -ur linux-2.4.5/drivers/usb/usb.c linux-2.4.5-tr5/drivers/usb/usb.c
--- linux-2.4.5/drivers/usb/usb.c Sat Apr 28 11:28:09 2001
+++ linux-2.4.5-tr5/drivers/usb/usb.c Tue May 29 18:22:19 2001
@@ -688,10 +688,12 @@
return -1;
}

+ down(&dev->serialize);
+
interface = dev->actconfig->interface + ifnum;

if (usb_interface_claimed(interface))
- return -1;
+ goto out_err;

private = NULL;
for (tmp = usb_driver_list.next; tmp != &usb_driver_list;) {
@@ -699,7 +701,6 @@
driver = list_entry(tmp, struct usb_driver, driver_list);
tmp = tmp->next;

- down(&driver->serialize);
id = driver->id_table;
/* new style driver? */
if (id) {
@@ -707,7 +708,9 @@
interface->act_altsetting = i;
id = usb_match_id(dev, interface, id);
if (id) {
+ down(&driver->serialize);
private = driver->probe(dev,ifnum,id);
+ up(&driver->serialize);
if (private != NULL)
break;
}
@@ -717,15 +720,21 @@
interface->act_altsetting = 0;
}
else /* "old style" driver */
+ {
+ down(&driver->serialize);
private = driver->probe(dev, ifnum, NULL);
+ up(&driver->serialize);
+ }

- up(&driver->serialize);
if (private) {
usb_driver_claim_interface(driver, interface, private);
+ up(&dev->serialize);
return 0;
}
}

+out_err:
+ up(&dev->serialize);
return -1;
}

@@ -924,6 +933,8 @@
atomic_set(&dev->refcnt, 1);
INIT_LIST_HEAD(&dev->inodes);
INIT_LIST_HEAD(&dev->filelist);
+
+ init_MUTEX(&dev->serialize);

dev->bus->op->allocate(dev);

diff -ur linux-2.4.5/include/linux/usb.h linux-2.4.5-tr5/include/linux/usb.h
--- linux-2.4.5/include/linux/usb.h Fri May 25 18:02:43 2001
+++ linux-2.4.5-tr5/include/linux/usb.h Tue May 29 18:12:33 2001
@@ -595,6 +595,7 @@
int slow; /* Slow device? */

atomic_t refcnt; /* Reference count */
+ struct semaphore serialize;

unsigned int toggle[2]; /* one bit for each endpoint ([0] = IN, [1] = OUT) */
unsigned int halted[2]; /* endpoint halts; one bit per endpoint # & direction; */
Two notes about parts missing from the patch:
1. Disconnect is not handled. I think the author intended to handle it
differently, with a usage count. See the source...
2. Drivers call claim_interface, and it seems they do it safely.
devio.c brackets it with lock_kernel/unlock_kernel. mdc800.c,
audio.c and acm.c do not attempt to claim something that they
do no own, so the old semaphore protects them.
-- Pete

----- End forwarded message -----
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2005-03-22 12:56    [W:0.039 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site