illegal context for sleeping ... rmmod ide-cd + ide-scsi

In lk 2.5.69 (and in 68) both the ide-cd and ide-scsi modules generate a "sleeping function called from illegal context" stack trace when removed.

After "rmmod ide-cd" this appears:
Debug: sleeping function called from illegal context

        at include/asm/semaphore.h:119
 Call Trace:
  [<c011dcec>] __might_sleep+0x5c/0x70
  [<c025b634>] auto_remove_settings+0x24/0x80
  [<c025db8a>] ide_unregister_subdriver+0x15a/0x3d0
  [<e10d48df>] ide_cdrom_cleanup+0x2f/0x110 [ide_cd]
  [<c02346de>] driver_unregister+0x2e/0x42
  [<e10d90e0>] ide_cdrom_driver+0x0/0xd8 [ide_cd]
  [<e10d91a8>] ide_cdrom_driver+0xc8/0xd8 [ide_cd]
  [<c025e270>] ide_unregister_driver+0x100/0x1df
  [<c0155f1f>] unmap_vma_list+0x1f/0x30
  [<e10d9200>] +0x0/0x140 [ide_cd]
  [<e10d4df2>] +0x12/0x20 [ide_cd]
  [<e10d90e0>] ide_cdrom_driver+0x0/0xd8 [ide_cd]
  [<c013d336>] sys_delete_module+0x1d6/0x240
  [<c0156457>] sys_munmap+0x57/0x80
  [<c0109eaf>] syscall_call+0x7/0xb

After "rmmod ide-scsi" this appears:
Debug: sleeping function called from illegal context

       at include/asm/semaphore.h:119
 Call Trace:
  [<e10c8068>] idescsi_driver+0xc8/0xd8 [ide_scsi]
  [<c011dcec>] __might_sleep+0x5c/0x70
  [<e10c8068>] idescsi_driver+0xc8/0xd8 [ide_scsi]
  [<c025b634>] auto_remove_settings+0x24/0x80
  [<c025db8a>] ide_unregister_subdriver+0x15a/0x3d0
  [<e10c7ff8>] idescsi_driver+0x58/0xd8 [ide_scsi]
  [<e10c7ff8>] idescsi_driver+0x58/0xd8 [ide_scsi]
  [<e10c542d>] idescsi_cleanup+0x1d/0x60 [ide_scsi]
  [<e10c7fa0>] idescsi_driver+0x0/0xd8 [ide_scsi]
  [<c025e270>] ide_unregister_driver+0x100/0x1df
  [<e10c6e87>] +0xfa/0x10f [ide_scsi]
  [<e10c8300>] +0x0/0x140 [ide_scsi]
  [<e10c663f>] +0x2f/0x50 [ide_scsi]
  [<e10c7fa0>] idescsi_driver+0x0/0xd8 [ide_scsi]
  [<c013d336>] sys_delete_module+0x1d6/0x240
  [<c0156457>] sys_munmap+0x57/0x80
  [<c0109eaf>] syscall_call+0x7/0xb

My .config has these kernel debugging options set:
#
# Kernel hacking
#
CONFIG_DEBUG_KERNEL=y CONFIG_DEBUG_STACKOVERFLOW=y CONFIG_DEBUG_SLAB=y
CONFIG_DEBUG_IOVIRT=y
CONFIG_MAGIC_SYSRQ=y CONFIG_DEBUG_SPINLOCK=y
CONFIG_KALLSYMS=y CONFIG_DEBUG_SPINLOCK_SLEEP=y CONFIG_FRAME_POINTER=y

Doug Gilbert

ide_unregister_subdriver() does spin_lock_irqsave(&ide_lock), then calls auto_remove_settings(), which does down(&ide_setting_sem);

A simple fix might be:

diff -puN drivers/ide/ide.c~ide_setting_sem-fix drivers/ide/ide.c
@@ -1131,13 +1131,12 @@ ide_settings_t *ide_find_setting_by_name
  *
  *	Automatically remove all the driver specific settings for this
  *	drive. This function may sleep and must not be called from IRQ
- *	context. Takes the settings_lock
+ *	context. The caller must hold ide_setting_sem.
  */
  
 static void auto_remove_settings (ide_drive_t *drive)
 {
 	ide_settings_t *setting;
-	down(&ide_setting_sem);
 repeat:
 	setting = drive->settings;
 	while (setting) {

@@ -1147,7 +1146,6 @@ repeat:
 		}
 		setting = setting->next;
 	}
-	up(&ide_setting_sem);
 }
 
 /**

@@ -2350,9 +2348,11 @@ int ide_unregister_subdriver (ide_drive_
 {
 	unsigned long flags;
 	
+	down(&ide_setting_sem);
 	spin_lock_irqsave(&ide_lock, flags);
 	if (drive->usage || drive->driver == &idedefault_driver || DRIVER(drive)->busy) {
 		spin_unlock_irqrestore(&ide_lock, flags);
+		up(&ide_setting_sem);
 		return 1;
 	}
 #if defined(CONFIG_BLK_DEV_IDEPNP) && defined(CONFIG_PNP) && defined(MODULE)

@@ -2363,6 +2363,7 @@ int ide_unregister_subdriver (ide_drive_
 	ide_remove_proc_entries(drive->proc, generic_subdriver_entries);
 #endif
 	auto_remove_settings(drive);
+	up(&ide_setting_sem);
 	drive->driver = &idedefault_driver;
 	setup_driver_defaults(drive);
 	spin_unlock_irqrestore(&ide_lock, flags);

_

Andrew,
Thanks. That patch clears the reported problem.

Doug Gilbert

This is already fixed in 2.4.x btw. Just hadn't got pushed into 2.5 yet

The 2.5.x code has another problem as well there is a basically unfixable deadlock in the proc and config stuff when flipping a device in and out of scsi mode