diff -urNp linux-2.5.26/include/asm-arm/system.h linux-2.5.26-schedfix/include/asm-arm/system.h
--- linux-2.5.26/include/asm-arm/system.h	Wed Jul 17 01:49:26 2002
+++ linux-2.5.26-schedfix/include/asm-arm/system.h	Fri Jul 19 15:44:20 2002
@@ -64,10 +64,9 @@ extern asmlinkage void __backtrace(void)
 struct thread_info;
 extern struct task_struct *__switch_to(struct thread_info *, struct thread_info *);
 
-#define prepare_arch_schedule(prev)		do { } while(0)
-#define finish_arch_schedule(prev)		do { } while(0)
-#define prepare_arch_switch(rq)			do { } while(0)
-#define finish_arch_switch(rq)			spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 #define switch_to(prev,next,last)					\
 	do {			 					\
diff -urNp linux-2.5.26/include/asm-i386/system.h linux-2.5.26-schedfix/include/asm-i386/system.h
--- linux-2.5.26/include/asm-i386/system.h	Wed Jul 17 01:49:22 2002
+++ linux-2.5.26-schedfix/include/asm-i386/system.h	Fri Jul 19 15:44:10 2002
@@ -11,10 +11,9 @@
 struct task_struct;	/* one of the stranger aspects of C forward declarations.. */
 extern void FASTCALL(__switch_to(struct task_struct *prev, struct task_struct *next));
 
-#define prepare_arch_schedule(prev)		do { } while(0)
-#define finish_arch_schedule(prev)		do { } while(0)
-#define prepare_arch_switch(rq)			do { } while(0)
-#define finish_arch_switch(rq)			spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 #define switch_to(prev,next,last) do {					\
 	asm volatile("pushl %%esi\n\t"					\
diff -urNp linux-2.5.26/include/asm-ia64/system.h linux-2.5.26-schedfix/include/asm-ia64/system.h
--- linux-2.5.26/include/asm-ia64/system.h	Wed Jul 17 01:49:32 2002
+++ linux-2.5.26-schedfix/include/asm-ia64/system.h	Fri Jul 19 13:40:26 2002
@@ -429,6 +429,10 @@ extern void ia64_load_extra (struct task
 } while (0)
 #endif
 
+#define prepare_arch_switch(rq, next)	do {spin_lock(&(next)->switch_lock); spin_unlock(&(rq)->lock);} while(0)
+#define finish_arch_switch(rq, prev)	do {spin_unlock_irq(&(prev)->switch_lock);} while(0)
+#define task_running(rq, p)	(((rq)->curr == (p)) || spin_is_locked(&(p)->switch_lock))
+
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */
diff -urNp linux-2.5.26/include/asm-ppc/system.h linux-2.5.26-schedfix/include/asm-ppc/system.h
--- linux-2.5.26/include/asm-ppc/system.h	Wed Jul 17 01:49:32 2002
+++ linux-2.5.26-schedfix/include/asm-ppc/system.h	Fri Jul 19 15:44:35 2002
@@ -83,10 +83,9 @@ extern void cacheable_memzero(void *p, u
 struct device_node;
 extern void note_scsi_host(struct device_node *, void *);
 
-#define prepare_arch_schedule(prev)		do { } while(0)
-#define finish_arch_schedule(prev)		do { } while(0)
-#define prepare_arch_switch(rq)			do { } while(0)
-#define finish_arch_switch(rq)			spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 struct task_struct;
 extern void __switch_to(struct task_struct *, struct task_struct *);
diff -urNp linux-2.5.26/include/asm-s390/system.h linux-2.5.26-schedfix/include/asm-s390/system.h
--- linux-2.5.26/include/asm-s390/system.h	Wed Jul 17 01:49:38 2002
+++ linux-2.5.26-schedfix/include/asm-s390/system.h	Fri Jul 19 15:44:03 2002
@@ -18,10 +18,9 @@
 #endif
 #include <linux/kernel.h>
 
-#define prepare_arch_schedule(prev)		do { } while (0)
-#define finish_arch_schedule(prev)		do { } while (0)
-#define prepare_arch_switch(rq)			do { } while (0)
-#define finish_arch_switch(rq)			spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 #define switch_to(prev,next,last) do {					     \
 	if (prev == next)						     \
diff -urNp linux-2.5.26/include/asm-s390x/system.h linux-2.5.26-schedfix/include/asm-s390x/system.h
--- linux-2.5.26/include/asm-s390x/system.h	Wed Jul 17 01:49:38 2002
+++ linux-2.5.26-schedfix/include/asm-s390x/system.h	Fri Jul 19 15:44:28 2002
@@ -18,10 +18,9 @@
 #endif
 #include <linux/kernel.h>
 
-#define prepare_arch_schedule(prev)		do { } while (0)
-#define finish_arch_schedule(prev)		do { } while (0)
-#define prepare_arch_switch(rq)			do { } while (0)
-#define finish_arch_switch(rq)			spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 #define switch_to(prev,next),last do {					     \
 	if (prev == next)						     \
diff -urNp linux-2.5.26/include/asm-sparc64/system.h linux-2.5.26-schedfix/include/asm-sparc64/system.h
--- linux-2.5.26/include/asm-sparc64/system.h	Wed Jul 17 01:49:22 2002
+++ linux-2.5.26-schedfix/include/asm-sparc64/system.h	Fri Jul 19 15:52:41 2002
@@ -144,13 +144,12 @@ extern void __flushw_user(void);
 #define flush_user_windows flushw_user
 #define flush_register_windows flushw_all
 
-#define prepare_arch_schedule(prev)	task_lock(prev)
-#define finish_arch_schedule(prev)	task_unlock(prev)
-#define prepare_arch_switch(rq)		\
-do {	spin_unlock(&(rq)->lock);	\
-	flushw_all();			\
-} while (0)
-#define finish_arch_switch(rq)		__sti()
+#define prepare_arch_switch(rq, next)	do {spin_lock(&(next)->switch_lock); \
+					    spin_unlock(&(rq)->lock);
+					    flushw_all(); \
+					} while(0)
+#define finish_arch_switch(rq, prev)	do {spin_unlock_irq(&(prev)->switch_lock);} while(0)
+#define task_running(rq, p)	(((rq)->curr == (p)) || spin_is_locked(&(p)->switch_lock))
 
 #ifndef CONFIG_DEBUG_SPINLOCK
 #define CHECK_LOCKS(PREV)	do { } while(0)
diff -urNp linux-2.5.26/include/asm-x86_64/system.h linux-2.5.26-schedfix/include/asm-x86_64/system.h
--- linux-2.5.26/include/asm-x86_64/system.h	Wed Jul 17 01:49:29 2002
+++ linux-2.5.26-schedfix/include/asm-x86_64/system.h	Fri Jul 19 15:44:42 2002
@@ -13,10 +13,9 @@
 #define LOCK_PREFIX ""
 #endif
 
-#define prepare_arch_schedule(prev)            do { } while(0)
-#define finish_arch_schedule(prev)             do { } while(0)
-#define prepare_arch_switch(rq)                        do { } while(0)
-#define finish_arch_switch(rq)                 spin_unlock_irq(&(rq)->lock)
+#define prepare_arch_switch(rq, next)	do { } while(0)
+#define finish_arch_switch(rq, prev)	spin_unlock_irq(&(rq)->lock)
+#define task_running(rq, p)		((rq)->curr == (p))
 
 #define __STR(x) #x
 #define STR(x) __STR(x)
diff -urNp linux-2.5.26/include/linux/init_task.h linux-2.5.26-schedfix/include/linux/init_task.h
--- linux-2.5.26/include/linux/init_task.h	Wed Jul 17 01:49:25 2002
+++ linux-2.5.26-schedfix/include/linux/init_task.h	Fri Jul 19 13:42:23 2002
@@ -78,6 +78,7 @@
     pending:		{ NULL, &tsk.pending.head, {{0}}},		\
     blocked:		{{0}},						\
     alloc_lock:		SPIN_LOCK_UNLOCKED,				\
+    switch_lock:	SPIN_LOCK_UNLOCKED,				\
     journal_info:	NULL,						\
 }
 
diff -urNp linux-2.5.26/include/linux/sched.h linux-2.5.26-schedfix/include/linux/sched.h
--- linux-2.5.26/include/linux/sched.h	Wed Jul 17 01:49:25 2002
+++ linux-2.5.26-schedfix/include/linux/sched.h	Fri Jul 19 13:40:26 2002
@@ -359,6 +359,8 @@ struct task_struct {
    	u32 self_exec_id;
 /* Protection of (de-)allocation: mm, files, fs, tty */
 	spinlock_t alloc_lock;
+/* context-switch lock */
+	spinlock_t switch_lock;
 
 /* journalling filesystem info */
 	void *journal_info;
diff -urNp linux-2.5.26/kernel/#sched.c.rej# linux-2.5.26-schedfix/kernel/#sched.c.rej#
--- linux-2.5.26/kernel/fork.c	Wed Jul 17 01:49:25 2002
+++ linux-2.5.26-schedfix/kernel/fork.c	Fri Jul 19 13:40:26 2002
@@ -675,6 +675,7 @@ struct task_struct *do_fork(unsigned lon
 		init_completion(&vfork);
 	}
 	spin_lock_init(&p->alloc_lock);
+	spin_lock_init(&p->switch_lock);
 
 	clear_tsk_thread_flag(p,TIF_SIGPENDING);
 	init_sigpending(&p->pending);
diff -urNp linux-2.5.26/kernel/sched.c linux-2.5.26-schedfix/kernel/sched.c
--- linux-2.5.26/kernel/sched.c	Wed Jul 17 01:49:29 2002
+++ linux-2.5.26-schedfix/kernel/sched.c	Fri Jul 19 16:09:39 2002
@@ -306,7 +306,7 @@ void wait_task_inactive(task_t * p)
 repeat:
 	preempt_disable();
 	rq = task_rq(p);
-	if (unlikely(rq->curr == p)) {
+	if (unlikely(task_running(rq, p))) {
 		cpu_relax();
 		/*
 		 * enable/disable preemption just to make this
@@ -317,7 +317,7 @@ repeat:
 		goto repeat;
 	}
 	rq = task_rq_lock(p, &flags);
-	if (unlikely(rq->curr == p)) {
+	if (unlikely(task_running(rq, p))) {
 		task_rq_unlock(rq, &flags);
 		preempt_enable();
 		goto repeat;
@@ -337,7 +337,7 @@ repeat:
  */
 void kick_if_running(task_t * p)
 {
-	if (p == task_rq(p)->curr)
+	if ((task_running(task_rq(p), p)) && (p->cpu != smp_processor_id()))
 		resched_task(p);
 }
 #endif
@@ -365,7 +365,7 @@ repeat_lock_task:
 		 * Fast-migrate the task if it's not running or runnable
 		 * currently. Do not violate hard affinity.
 		 */
-		if (unlikely(sync && (rq->curr != p) &&
+		if (unlikely(sync && !task_running(rq, p) &&
 			(task_cpu(p) != smp_processor_id()) &&
 			(p->cpus_allowed & (1UL << smp_processor_id())))) {
 
@@ -443,8 +443,7 @@ void sched_exit(task_t * p)
 #if CONFIG_SMP || CONFIG_PREEMPT
 asmlinkage void schedule_tail(task_t *prev)
 {
-	finish_arch_switch(this_rq());
-	finish_arch_schedule(prev);
+	finish_arch_switch(this_rq(), prev);
 }
 #endif
 
@@ -646,7 +645,7 @@ skip_queue:
 
 #define CAN_MIGRATE_TASK(p,rq,this_cpu)					\
 	((jiffies - (p)->sleep_timestamp > cache_decay_ticks) &&	\
-		((p) != (rq)->curr) &&					\
+		((p) != (rq)->curr) &&	!task_running(rq, p)  &&	\
 			((p)->cpus_allowed & (1UL << (this_cpu))))
 
 	if (!CAN_MIGRATE_TASK(tmp, busiest, this_cpu)) {
@@ -816,7 +815,6 @@ need_resched:
 	rq = this_rq();
 
 	release_kernel_lock(prev, smp_processor_id());
-	prepare_arch_schedule(prev);
 	prev->sleep_timestamp = jiffies;
 	spin_lock_irq(&rq->lock);
 
@@ -873,11 +871,11 @@ switch_tasks:
 		rq->nr_switches++;
 		rq->curr = next;
 	
-		prepare_arch_switch(rq);
+		prepare_arch_switch(rq, next);
 		prev = context_switch(prev, next);
 		barrier();
 		rq = this_rq();
-		finish_arch_switch(rq);
+		finish_arch_switch(rq, prev);
 	} else
 		spin_unlock_irq(&rq->lock);
 	finish_arch_schedule(prev);
@@ -1106,7 +1104,7 @@ void set_user_nice(task_t *p, long nice)
 		 * If the task is running and lowered its priority,
 		 * or increased its priority then reschedule its CPU:
 		 */
-		if ((NICE_TO_PRIO(nice) < p->static_prio) || (p == rq->curr))
+		if ((NICE_TO_PRIO(nice) < p->static_prio) || task_running(rq, p))
 			resched_task(rq->curr);
 	}
 out_unlock:
@@ -1779,7 +1777,7 @@ void set_cpus_allowed(task_t *p, unsigne
 	 * If the task is not on a runqueue (and not running), then
 	 * it is sufficient to simply update the task's cpu field.
 	 */
-	if (!p->array && (p != rq->curr)) {
+	if (!p->array && !task_running(rq, p)) {
 		set_task_cpu(p, __ffs(p->cpus_allowed));
 		task_rq_unlock(rq, &flags);
 		goto out;