[PATCH] (5/5) improved notifier callback mechanism -- remove old

[Stephen Hemminger]

After the previous patches, the notifier interface now has it's own
locking.  Therefore the existing locking done by the profile interface
is superfluous.

This has been tested by repeated loading/unloading the oprofile driver
while profiling was on.

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or
higher.
# This patch includes the following deltas:
#	           ChangeSet	1.985   -> 1.986  
#	arch/i386/kernel/profile.c	1.2     -> 1.3    
#	    kernel/profile.c	1.4     -> 1.5    
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/12/17	[e-mail]	1.986
# Locking now handled by notifier
# --------------------------------------------
#
diff -Nru a/arch/i386/kernel/profile.c b/arch/i386/kernel/profile.c
--- a/arch/i386/kernel/profile.c	Tue Dec 17 11:25:47 2002
+++ b/arch/i386/kernel/profile.c	Tue Dec 17 11:25:47 2002
@@ -6,40 +6,25 @@
  */
 
 #include <linux/profile.h>
-#include <linux/spinlock.h>
 #include <linux/notifier.h>
 #include <linux/irq.h>
 #include <asm/hw_irq.h> 
  
 static LIST_HEAD(profile_listeners);
-static rwlock_t profile_lock = RW_LOCK_UNLOCKED;
  
 int register_profile_notifier(struct notifier_block * nb)
 {
-	int err;
-	write_lock_irq(&profile_lock);
-	err = notifier_chain_register(&profile_listeners, nb);
-	write_unlock_irq(&profile_lock);
-	return err;
+	return notifier_chain_register(&profile_listeners, nb);
 }
 
 
 int unregister_profile_notifier(struct notifier_block * nb)
 {
-	int err;
-	write_lock_irq(&profile_lock);
-	err = notifier_chain_unregister(&profile_listeners, nb);
-	write_unlock_irq(&profile_lock);
-	return err;
+	return notifier_chain_unregister(&profile_listeners, nb);
 }
 
 
 void x86_profile_hook(struct pt_regs * regs)
 {
-	/* we would not even need this lock if
-	 * we had a global cli() on register/unregister
-	 */ 
-	read_lock(&profile_lock);
 	notifier_call_chain(&profile_listeners, 0, regs);
-	read_unlock(&profile_lock);
 }
diff -Nru a/kernel/profile.c b/kernel/profile.c
--- a/kernel/profile.c	Tue Dec 17 11:25:47 2002
+++ b/kernel/profile.c	Tue Dec 17 11:25:47 2002
@@ -47,38 +47,29 @@
  
 #ifdef CONFIG_PROFILING
  
-static DECLARE_RWSEM(profile_rwsem);
 static LIST_HEAD(exit_task_notifier);
 static LIST_HEAD(exit_mmap_notifier);
 static LIST_HEAD(exec_unmap_notifier);
  
 void profile_exit_task(struct task_struct * task)
 {
-	down_read(&profile_rwsem);
 	notifier_call_chain(&exit_task_notifier, 0, task);
-	up_read(&profile_rwsem);
 }
  
 void profile_exit_mmap(struct mm_struct * mm)
 {
-	down_read(&profile_rwsem);
 	notifier_call_chain(&exit_mmap_notifier, 0, mm);
-	up_read(&profile_rwsem);
 }
 
 void profile_exec_unmap(struct mm_struct * mm)
 {
-	down_read(&profile_rwsem);
 	notifier_call_chain(&exec_unmap_notifier, 0, mm);
-	up_read(&profile_rwsem);
 }
 
 int profile_event_register(enum profile_type type, struct
notifier_block * n)
 {
 	int err = -EINVAL;
  
-	down_write(&profile_rwsem);
- 
 	switch (type) {
 		case EXIT_TASK:
 			err = notifier_chain_register(&exit_task_notifier, n);
@@ -91,8 +82,6 @@
 			break;
 	}
  
-	up_write(&profile_rwsem);
- 
 	return err;
 }
 
@@ -101,8 +90,6 @@
 {
 	int err = -EINVAL;
  
-	down_write(&profile_rwsem);
- 
 	switch (type) {
 		case EXIT_TASK:
 			err = notifier_chain_unregister(&exit_task_notifier, n);
@@ -115,7 +102,6 @@
 			break;
 	}
 
-	up_write(&profile_rwsem);
 	return err;
 }