Re: [patch 0/8] mutex subsystem, -V6

[Nicolas Pitre <nico@cam.org>]

On Fri, 23 Dec 2005, Ingo Molnar wrote:

> this is verion -V6 of the generic mutex subsystem.

Here's a patch to fix a few minor things: some comments were wrong, some 
were irrelevant, another was duplicated.  Also remove a bogus "return 0".

Index: linux-2.6/include/asm-generic/mutex-dec.h
===================================================================
--- linux-2.6.orig/include/asm-generic/mutex-dec.h
+++ linux-2.6/include/asm-generic/mutex-dec.h
@@ -1,7 +1,7 @@
 /*
  * asm-generic/mutex-dec.h
  *
- * Generic wrappers for the mutex fastpath based on an xchg() implementation
+ * Generic wrappers for the mutex fastpath based on atomic increment/decrement
  *
  */
 #ifndef _ASM_GENERIC_MUTEX_DEC_H
@@ -46,7 +46,7 @@ __mutex_fastpath_lock_retval(atomic_t *c
 /**
  *  __mutex_fastpath_unlock - try to promote the mutex from 0 to 1
  *  @count: pointer of type atomic_t
- *  @fn: function to call if the original value was not 1
+ *  @fn: function to call if the original value was not 0
  *
  * try to promote the mutex from 0 to 1. if it wasn't 0, call <function>
  * In the failure case, this function is allowed to either set the value to
Index: linux-2.6/include/asm-generic/mutex-xchg.h
===================================================================
--- linux-2.6.orig/include/asm-generic/mutex-xchg.h
+++ linux-2.6/include/asm-generic/mutex-xchg.h
@@ -51,7 +51,7 @@ __mutex_fastpath_lock_retval(atomic_t *c
 /**
  *  __mutex_fastpath_unlock - try to promote the mutex from 0 to 1
  *  @count: pointer of type atomic_t
- *  @fn: function to call if the original value was not 1
+ *  @fn: function to call if the original value was not 0
  *
  * try to promote the mutex from 0 to 1. if it wasn't 0, call <function>
  * In the failure case, this function is allowed to either set the value to
Index: linux-2.6/include/asm-i386/mutex.h
===================================================================
--- linux-2.6.orig/include/asm-i386/mutex.h
+++ linux-2.6/include/asm-i386/mutex.h
@@ -61,7 +61,7 @@ __mutex_fastpath_lock_retval(atomic_t *c
 /**
  *  __mutex_fastpath_unlock - try to promote the mutex from 0 to 1
  *  @count: pointer of type atomic_t
- *  @fn: function to call if the original value was not 1
+ *  @fn: function to call if the original value was not 0
  *
  * try to promote the mutex from 0 to 1. if it wasn't 0, call <function>
  * In the failure case, this function is allowed to either set the value to
Index: linux-2.6/kernel/mutex.c
===================================================================
--- linux-2.6.orig/kernel/mutex.c
+++ linux-2.6/kernel/mutex.c
@@ -344,10 +344,6 @@ static inline void __mutex_unlock_nonato
 static __sched void FASTCALL(__mutex_lock_noinline(atomic_t *lock_count));
 
 /*
- * Some architectures do not have fast dec_and_test atomic primitives,
- * for them we are providing an atomic_xchg() based mutex implementation,
- * if they enable CONFIG_MUTEX_XCHG_ALGORITHM.
- *
  * The locking fastpath is the 1->0 transition from 'unlocked' into
  * 'locked' state:
  */
@@ -356,11 +352,6 @@ static inline void __mutex_lock_atomic(s
 	__mutex_fastpath_lock(&lock->count, __mutex_lock_noinline);
 }
 
-/*
- * We put the slowpath into a separate function. This reduces
- * register pressure in the fastpath, and also enables the
- * atomic_[inc/dec]_call_if_[negative|nonpositive]() primitives.
- */
 static void fastcall __sched __mutex_lock_noinline(atomic_t *lock_count)
 {
 	struct mutex *lock = container_of(lock_count, struct mutex, count);
@@ -380,7 +371,6 @@ static inline int __mutex_lock_interrupt
 {
 	return __mutex_fastpath_lock_retval
 			(&lock->count, __mutex_lock_interruptible_noinline);
-	return 0;
 }
 
 static int fastcall __sched