> One way to look at that issue is to ask what user mode notifications
> will be used to address that part of the hotplug problem. Devfsd
> is what some folk like, but it's not universally accepted. GUI
> driven solutions don't seem right in all cases either.
devfsd is at least already here. The existing /sbin/hotplug architecture
can't handle it. A new kind of event would be needed.
Even so, you'll probably won't make the user happy if it works only
on plugging in and not when he puts in a new medium.
A look at supermount might be in order.
> As I understand things, USB-to-SCSI adapters (like most usb-storage
> devices) will also have "bus" add/remove events to deal with. Likewise
> with cases like hotplugging a SCSI controller on a Cardbus laptop, or on a
> CompactPCI (or HotplugPCI) enterprise level server. Presumably those cases
> aren't as troublesome?
Yes, a new bus is scanned anyway.
To a certain extent the notion of bus vs. device becomes moot, when devices
are identified by globally unique numbers. Should a fibre channel drive be
given other names if it's shifted to another controller ?
To let deeds follow words I've attached a patch that adds error reporting and
locking to the bus removal functions.
Regards
Oliver
--- linux-vanilla/drivers/scsi/scsi.c Mon Jan 1 14:28:32 2001
+++ linux/drivers/scsi/scsi.c Sat Jan 6 00:41:38 2001
@@ -53,6 +53,7 @@
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init.h>
+#include <linux/smp_lock.h>
#define __KERNEL_SYSCALLS__
@@ -1376,7 +1377,7 @@
}
static int scsi_register_host(Scsi_Host_Template *);
-static void scsi_unregister_host(Scsi_Host_Template *);
+static int scsi_unregister_host(Scsi_Host_Template *);
/*
* Function: scsi_release_commandblocks()
@@ -1963,14 +1964,8 @@
/*
* Similarly, this entry point should be called by a loadable module if it
* is trying to remove a low level scsi driver from the system.
- *
- * Note - there is a fatal flaw in the deregister module function.
- * There is no way to return a code that says 'I cannot be unloaded now'.
- * The system relies entirely upon usage counts that are maintained,
- * and the assumption is that if the usage count is 0, then the module
- * can be unloaded.
*/
-static void scsi_unregister_host(Scsi_Host_Template * tpnt)
+static int scsi_unregister_host(Scsi_Host_Template * tpnt)
{
int online_status;
int pcount0, pcount;
@@ -1982,6 +1977,9 @@
struct Scsi_Host *shpnt;
char name[10]; /* host_no>=10^9? I don't think so. */
+ /* get the big kernel lock, so we don't race with open() */
+ lock_kernel();
+
/*
* First verify that this host adapter is completely free with no pending
* commands
@@ -1992,7 +1990,7 @@
if (SDpnt->host->hostt == tpnt
&& SDpnt->host->hostt->module
&& GET_USE_COUNT(SDpnt->host->hostt->module))
- return;
+ goto err_out;
/*
* FIXME(eric) - We need to find a way to notify the
* low level driver that we are shutting down - via the
@@ -2044,7 +2042,7 @@
}
SDpnt->online = online_status;
printk(KERN_ERR "Device busy???\n");
- return;
+ goto err_out;
}
/*
* No, this device is really free. Mark it as such, and
@@ -2070,7 +2068,7 @@
/* If something still attached, punt */
if (SDpnt->attached) {
printk(KERN_ERR "Attached usage count = %d\n", SDpnt->attached);
- return;
+ goto err_out;
}
devfs_unregister (SDpnt->de);
}
@@ -2178,6 +2176,13 @@
}
}
MOD_DEC_USE_COUNT;
+
+ unlock_kernel();
+ return 0;
+
+err_out:
+ unlock_kernel();
+ return -1;
}
static int scsi_unregister_device(struct Scsi_Device_Template *tpnt);
@@ -2259,12 +2264,13 @@
struct Scsi_Host *shpnt;
struct Scsi_Device_Template *spnt;
struct Scsi_Device_Template *prev_spnt;
-
+
+ lock_kernel();
/*
* If we are busy, this is not going to fly.
*/
if (GET_USE_COUNT(tpnt->module) != 0)
- return 0;
+ goto error_out;
/*
* Next, detach the devices from the driver.
@@ -2301,11 +2307,15 @@
prev_spnt->next = spnt->next;
MOD_DEC_USE_COUNT;
+ unlock_kernel();
/*
* Final cleanup for the driver is done in the driver sources in the
* cleanup function.
*/
return 0;
+error_out:
+ unlock_kernel();
+ return -1;
}
@@ -2342,22 +2352,24 @@
/* Reverse the actions taken above
*/
-void scsi_unregister_module(int module_type, void *ptr)
+int scsi_unregister_module(int module_type, void *ptr)
{
+ int retval = 0;
+
switch (module_type) {
case MODULE_SCSI_HA:
- scsi_unregister_host((Scsi_Host_Template *) ptr);
+ retval = scsi_unregister_host((Scsi_Host_Template *) ptr);
break;
case MODULE_SCSI_DEV:
- scsi_unregister_device((struct Scsi_Device_Template *) ptr);
- break;
+ retval = scsi_unregister_device((struct Scsi_Device_Template *)ptr);
+ break;
/* The rest of these are not yet implemented. */
case MODULE_SCSI_CONST:
case MODULE_SCSI_IOCTL:
break;
default:
}
- return;
+ return retval;
}
#ifdef CONFIG_PROC_FS
