From e769da08d9f4caebda003b22c6f07c97e1d23e4f Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Wed, 6 Dec 2006 20:36:13 -0800
Subject: [PATCH] --- yaml --- r: 42785 b: refs/heads/master c:
 9a2239b1174bdf0952a21ed328cd74240d2dd173 h: refs/heads/master i:   42783:
 ba7bbc3d3331011ac153a2548257ae820109a03b v: v3

---
 [refs]                  |  2 +-
 trunk/drivers/ide/ide.c | 19 +++++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/[refs] b/[refs]
index eda59019ffd8..5de2e4d33114 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 23a1b2a78705caa2ecaccf8422a1e22eaca59574
+refs/heads/master: 9a2239b1174bdf0952a21ed328cd74240d2dd173
diff --git a/trunk/drivers/ide/ide.c b/trunk/drivers/ide/ide.c
index 287a66201150..16890769dca6 100644
--- a/trunk/drivers/ide/ide.c
+++ b/trunk/drivers/ide/ide.c
@@ -973,8 +973,8 @@ ide_settings_t *ide_find_setting_by_name (ide_drive_t *drive, char *name)
  *	@drive: drive
  *
  *	Automatically remove all the driver specific settings for this
- *	drive. This function may sleep and must not be called from IRQ
- *	context. The caller must hold ide_setting_sem.
+ *	drive. This function may not be called from IRQ context. The
+ *	caller must hold ide_setting_sem.
  */
  
 static void auto_remove_settings (ide_drive_t *drive)
@@ -1874,11 +1874,22 @@ void ide_unregister_subdriver(ide_drive_t *drive, ide_driver_t *driver)
 {
 	unsigned long flags;
 	
-	down(&ide_setting_sem);
-	spin_lock_irqsave(&ide_lock, flags);
 #ifdef CONFIG_PROC_FS
 	ide_remove_proc_entries(drive->proc, driver->proc);
 #endif
+	down(&ide_setting_sem);
+	spin_lock_irqsave(&ide_lock, flags);
+	/*
+	 * ide_setting_sem protects the settings list
+	 * ide_lock protects the use of settings
+	 *
+	 * so we need to hold both, ide_settings_sem because we want to
+	 * modify the settings list, and ide_lock because we cannot take
+	 * a setting out that is being used.
+	 *
+	 * OTOH both ide_{read,write}_setting are only ever used under
+	 * ide_setting_sem.
+	 */
 	auto_remove_settings(drive);
 	spin_unlock_irqrestore(&ide_lock, flags);
 	up(&ide_setting_sem);