[Linux-ia64] Re: O(1) MQ scheduler J9 patch for IA64 -> K3 patch

[Erich Focht <focht@ess.nec.de>]

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On Thu, 7 Feb 2002, David Mosberger wrote:

>   Erich> I had to add a function smp_call_function_nowait which sends
>   Erich> an IPI and returns immediately in order to get rid of a
>   Erich> IA64-specific race condition when the mmu_context wraps
>   Erich> around. Now it makes a very stable and fast impression,
>   Erich> interactive work is even possible while doing a "hackbench
>   Erich> 55" and ping flooding the machine... Tested on 2 CPU BigSur,
>   Erich> 4 CPU LION, 16 CPU AzusA.
> 
> Hmmh, I'm a bit worried that this is a fragile solution.  It would
> break if there ever was a scenario where a task migrated from one CPU
> to another while the target CPU has interrupts disabled.  I do not
> think this can happen with Ingo's current scheduler but I'd prefer a
> more robust solution.
> 
> A somewhat cheesy solution might be to have a per-CPU flag that
> indicates whether a CPU should flush its TLB before switching to the
> next task.  We could check for this in activate_mm().  Do you want to
> try this?

OK, I also feel better with the new solution. Didn't want to put it into
the runqueues because it really is an IA-64 problem. It's
architecture-specific and the CPU flags are in ia64_ctx. The context
wrapping is so seldom that the single lock protecting the CPU mask
shouldn't matter. But if somebody decides to use this mechanism generally
for flush_tlb_all() we'd have to change it...

Besides this: the attached patch is for the latest version of the
O(1) scheduler (K3). It has a different sys_sched_yield() from Ingo's
because that one has a problem with more than 8 CPUs. Also the
set_cpus_allowed() function has the limitation that it just works if the
current process tries to change its mask.

Best regards,
Erich


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diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kdb/kdba_bt.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kdb/kdba_bt.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kdb/kdba_bt.c	Mon Feb  4 12:42:05 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kdb/kdba_bt.c	Fri Feb  8 12:11:24 2002
@@ -197,7 +197,7 @@
 	}
 #ifdef CONFIG_SMP
 	else if (task_has_cpu(p)) {
-		sw = kdb_sw[p->processor];
+		sw = kdb_sw[p->cpu];
 	}
 #endif
 	else {
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/entry.S 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/entry.S
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/entry.S	Mon Feb  4 12:41:37 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/entry.S	Fri Feb  8 12:11:24 2002
@@ -161,7 +161,8 @@
 	mov r8=r13			// return pointer to previously running task
 	mov r13=in0			// set "current" pointer
 	;;
-(p6)	ssm psr.i			// renable psr.i AFTER the ic bit is serialized
+//(p6)	ssm psr.i			// interrupt delivery should not be enabled
+					// with the new O(1) MQ scheduler
 	DO_LOAD_SWITCH_STACK
 
 #ifdef CONFIG_SMP
@@ -170,7 +171,8 @@
 	br.ret.sptk.many rp		// boogie on out in new context
 
 .map:
-	rsm psr.i | psr.ic
+	//rsm psr.i | psr.ic
+	rsm psr.ic
 	movl r25=PAGE_KERNEL
 	;;
 	srlz.d
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/irq_ia64.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/irq_ia64.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/irq_ia64.c	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/irq_ia64.c	Fri Feb  8 12:11:24 2002
@@ -148,6 +148,14 @@
 	flags:		SA_INTERRUPT,
 	name:		"IPI"
 };
+
+extern void smp_task_migration_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+
+static struct irqaction task_migration_irqaction = {
+	handler:	smp_task_migration_interrupt,
+	flags:		SA_INTERRUPT,
+	name:		"Task migration"
+};
 #endif
 
 void
@@ -172,6 +180,7 @@
 	register_percpu_irq(IA64_SPURIOUS_INT_VECTOR, NULL);
 #ifdef CONFIG_SMP
 	register_percpu_irq(IA64_IPI_VECTOR, &ipi_irqaction);
+	register_percpu_irq(IA64_TASK_MIGRATION, &task_migration_irqaction);
 #endif
 	platform_irq_init();
 }
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/process.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/process.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/process.c	Mon Feb  4 12:41:37 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/process.c	Fri Feb  8 12:11:24 2002
@@ -125,9 +125,6 @@
 cpu_idle (void *unused)
 {
 	/* endless idle loop with no priority at all */
-	init_idle();
-	current->nice = 20;
-	current->counter = -100;
 
 
 	while (1) {
@@ -136,11 +133,10 @@
 			min_xtp();
 #endif
 
-		while (!current->need_resched) {
+		if (!current->need_resched) {
 #ifdef CONFIG_IA64_SGI_SN
 			snidle();
 #endif
-			continue;
 		}
 
 #ifdef CONFIG_IA64_SGI_SN
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/setup.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/setup.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/setup.c	Mon Feb  4 12:41:37 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/setup.c	Fri Feb  8 12:11:24 2002
@@ -375,10 +375,10 @@
 {
 #ifdef CONFIG_SMP
 #	define lpj	c->loops_per_jiffy
-#	define cpu	c->processor
+#	define cpum	c->processor
 #else
 #	define lpj	loops_per_jiffy
-#	define cpu	0
+#	define cpum	0
 #endif
 	char family[32], features[128], *cp;
 	struct cpuinfo_ia64 *c = v;
@@ -417,7 +417,7 @@
 		   "cpu MHz    : %lu.%06lu\n"
 		   "itc MHz    : %lu.%06lu\n"
 		   "BogoMIPS   : %lu.%02lu\n\n",
-		   cpu, c->vendor, family, c->model, c->revision, c->archrev,
+		   cpum, c->vendor, family, c->model, c->revision, c->archrev,
 		   features, c->ppn, c->number,
 		   c->proc_freq / 1000000, c->proc_freq % 1000000,
 		   c->itc_freq / 1000000, c->itc_freq % 1000000,
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/smp.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/smp.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/smp.c	Mon Feb  4 12:42:05 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/smp.c	Fri Feb  8 12:42:35 2002
@@ -200,6 +200,42 @@
 }
 
 void
+smp_send_reschedule_all(void)
+{
+	send_IPI_all(IA64_IPI_RESCHEDULE);
+}
+
+static spinlock_t migration_lock = SPIN_LOCK_UNLOCKED;
+static task_t *new_task;
+
+
+/*
+ * This function sends a 'task migration' IPI to another CPU.
+ * Must be called from syscall contexts, with interrupts *enabled*.
+ */
+void smp_migrate_task(int cpu, task_t *p)
+{
+	/*
+	 * The target CPU will unlock the migration spinlock:
+	 */
+	spin_lock(&migration_lock);
+	new_task = p;
+	platform_send_ipi(cpu, IA64_TASK_MIGRATION, IA64_IPI_DM_INT, 0);
+}
+
+/*
+ * Task migration callback.
+ */
+asmlinkage void smp_task_migration_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+{
+	task_t *p;
+
+	p = new_task;
+	spin_unlock(&migration_lock);
+	sched_task_migrated(p);
+}
+
+void
 smp_flush_tlb_all (void)
 {
 	smp_call_function ((void (*)(void *))__flush_tlb_all,0,1,1);
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/smpboot.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/smpboot.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/smpboot.c	Mon Feb  4 12:41:37 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/smpboot.c	Fri Feb  8 12:11:24 2002
@@ -356,6 +356,7 @@
 	local_irq_enable();
 	calibrate_delay();
 	local_cpu_data->loops_per_jiffy = loops_per_jiffy;
+	ia64_disable_timer();
 	/*
 	 * Allow the master to continue.
 	 */
@@ -379,7 +380,8 @@
 	Dprintk("CPU %d is set to go.\n", smp_processor_id());
 	while (!atomic_read(&smp_commenced))
 		;
-
+	/* reenable timer interrupts */
+	ia64_cpu_local_tick();
 	Dprintk("CPU %d is starting idle.\n", smp_processor_id());
 	return cpu_idle();
 }
@@ -416,11 +418,10 @@
 	if (!idle)
 		panic("No idle process for CPU %d", cpu);
 
-	task_set_cpu(idle, cpu);	/* we schedule the first task manually */
+	init_idle(idle, cpu);
 
 	ia64_cpu_to_sapicid[cpu] = sapicid;
 
-	del_from_runqueue(idle);
 	unhash_process(idle);
 	init_tasks[cpu] = idle;
 
@@ -481,8 +482,7 @@
 	printk("Boot processor id 0x%x/0x%x\n", 0, boot_cpu_id);
 
 	global_irq_holder = 0;
-	current->processor = 0;
-	init_idle();
+	current->cpu = 0;
 
 	/*
 	 * If SMP should be disabled, then really disable it!
@@ -569,3 +569,9 @@
 		smp_num_cpus = 1;
 	}
 }
+
+/* Number of ticks we consider an idle tasks still cache-hot.
+ * For Itanium: with 1GB/s bandwidth we need 4ms to fill up 4MB L3 cache...
+ * So let's try 10 ticks.
+ */
+unsigned long cache_decay_ticks=10;
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/time.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/time.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/kernel/time.c	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/kernel/time.c	Fri Feb  8 12:11:24 2002
@@ -209,7 +209,7 @@
 /*
  * Encapsulate access to the itm structure for SMP.
  */
-void __init
+void
 ia64_cpu_local_tick (void)
 {
 	int cpu = smp_processor_id();
@@ -298,3 +298,9 @@
 	efi_gettimeofday((struct timeval *) &xtime);
 	ia64_init_itm();
 }
+
+void __init ia64_disable_timer(void)
+{
+	ia64_set_itv(IA64_TIMER_VECTOR | IA64_TIMER_MASK);
+}
+
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/mm/fault.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/mm/fault.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/mm/fault.c	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/mm/fault.c	Fri Feb  8 12:11:24 2002
@@ -194,8 +194,7 @@
   out_of_memory:
 	up_read(&mm->mmap_sem);
 	if (current->pid == 1) {
-		current->policy |= SCHED_YIELD;
-		schedule();
+		yield();
 		down_read(&mm->mmap_sem);
 		goto survive;
 	}
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/mm/tlb.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/mm/tlb.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/mm/tlb.c	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/mm/tlb.c	Fri Feb  8 13:06:21 2002
@@ -37,7 +37,8 @@
 	lock:	SPIN_LOCK_UNLOCKED,
 	next:	1,
 	limit:	(1 << 15) - 1,		/* start out with the safe (architected) limit */
-	max_ctx: ~0U
+	max_ctx: ~0U,
+	flush: 0UL
 };
 
 /*
@@ -76,7 +77,9 @@
 			ia64_ctx.limit = tsk_context;
 	}
 	read_unlock(&tasklist_lock);
-	flush_tlb_all();
+	//flush_tlb_all(); /* potential race condition with O(1) scheduler [EF] */
+	ia64_ctx.flush = ((1<<smp_num_cpus) - 1) & ~(1UL<<smp_processor_id());
+	__flush_tlb_all();
 }
 
 static inline void
diff -urN 2.4.17-ia64-kdbv2.1-K3/arch/ia64/tools/print_offsets.c 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/tools/print_offsets.c
--- 2.4.17-ia64-kdbv2.1-K3/arch/ia64/tools/print_offsets.c	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/arch/ia64/tools/print_offsets.c	Fri Feb  8 12:11:24 2002
@@ -54,7 +54,7 @@
     { "IA64_TASK_PTRACE_OFFSET",	offsetof (struct task_struct, ptrace) },
     { "IA64_TASK_SIGPENDING_OFFSET",	offsetof (struct task_struct, sigpending) },
     { "IA64_TASK_NEED_RESCHED_OFFSET",	offsetof (struct task_struct, need_resched) },
-    { "IA64_TASK_PROCESSOR_OFFSET",	offsetof (struct task_struct, processor) },
+    { "IA64_TASK_PROCESSOR_OFFSET",	offsetof (struct task_struct, cpu) },
     { "IA64_TASK_THREAD_OFFSET",	offsetof (struct task_struct, thread) },
     { "IA64_TASK_THREAD_KSP_OFFSET",	offsetof (struct task_struct, thread.ksp) },
 #ifdef CONFIG_PERFMON
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/bitops.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/bitops.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/bitops.h	Mon Feb  4 12:41:38 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/bitops.h	Fri Feb  8 12:11:24 2002
@@ -280,6 +280,20 @@
 	return result;
 }
 
+/**
+ * __ffs - find first bit in a 64 bit long.
+ *
+ * Undefined if no bit exists, so code should check against 0 first.
+ */
+static inline unsigned long
+__ffs (unsigned long x)
+{
+	unsigned long result;
+
+	__asm__ ("popcnt %0=%1" : "=r" (result) : "r" (~x & (x - 1)));
+	return result;
+}
+
 #ifdef __KERNEL__
 
 /*
@@ -357,6 +371,8 @@
 	tmp = *p;
 found_first:
 	tmp |= ~0UL << size;
+	if (tmp == ~0UL)        /* Are any bits zero? */
+		return result + size; /* Nope. */
 found_middle:
 	return result + ffz(tmp);
 }
@@ -366,8 +382,52 @@
  */
 #define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
 
+/*
+ * Find next bit in a bitmap reasonably efficiently..
+ */
+static inline int
+find_next_bit (void *addr, unsigned long size, unsigned long offset)
+{
+	unsigned long *p = ((unsigned long *) addr) + (offset >> 6);
+	unsigned long result = offset & ~63UL;
+	unsigned long tmp;
+
+	if (offset >= size)
+		return size;
+	size -= result;
+	offset &= 63UL;
+	if (offset) {
+		tmp = *(p++);
+		tmp &= ~0UL << offset;
+		if (size < 64)
+			goto found_first;
+		if (tmp)
+			goto found_middle;
+		size -= 64;
+		result += 64;
+	}
+	while (size & ~63UL) {
+		if ((tmp = *(p++)))
+			goto found_middle;
+		result += 64;
+		size -= 64;
+	}
+	if (!size)
+		return result;
+	tmp = *p;
+found_first:
+	tmp &= ~0UL >> (64-size);
+	if (tmp == 0UL)        /* Are any bits set? */
+		return result + size; /* Nope. */
+found_middle:
+	return result + __ffs(tmp);
+}
+
+#define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
+
 #ifdef __KERNEL__
 
+#define __clear_bit(nr, addr)        clear_bit(nr, addr)
 #define ext2_set_bit                 test_and_set_bit
 #define ext2_clear_bit               test_and_clear_bit
 #define ext2_test_bit                test_bit
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/hw_irq.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/hw_irq.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/hw_irq.h	Tue Jul 31 19:30:09 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/hw_irq.h	Fri Feb  8 12:11:24 2002
@@ -49,6 +49,7 @@
 #define IA64_PERFMON_VECTOR		0xee	/* performanc monitor interrupt vector */
 #define IA64_TIMER_VECTOR		0xef	/* use highest-prio group 15 interrupt for timer */
 #define	IA64_MCA_WAKEUP_VECTOR		0xf0	/* MCA wakeup (must be >MCA_RENDEZ_VECTOR) */
+#define IA64_TASK_MIGRATION		0xfb	/* task migration interrupt vector */
 #define IA64_IPI_RESCHEDULE		0xfd	/* SMP reschedule */
 #define IA64_IPI_VECTOR			0xfe	/* inter-processor interrupt vector */
 
@@ -65,6 +66,9 @@
         IA64_IPI_DM_EXTINT =    0x7,    /* pend an 8259-compatible interrupt. */
 };
 
+/* bit for masking and discarding timer interrupts on IA64 */
+#define IA64_TIMER_MASK         (1<<16)
+
 extern __u8 isa_irq_to_vector_map[16];
 #define isa_irq_to_vector(x)	isa_irq_to_vector_map[(x)]
 
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/mmu_context.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/mmu_context.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/mmu_context.h	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/mmu_context.h	Fri Feb  8 12:56:09 2002
@@ -33,6 +33,9 @@
 	unsigned int next;	/* next context number to use */
 	unsigned int limit;	/* next >= limit => must call wrap_mmu_context() */
 	unsigned int max_ctx;	/* max. context value supported by all CPUs */
+	unsigned long flush;    /* CPU mask for those which have to perform a
+				 * local TLB flush before switching the context.
+				 */
 };
 
 extern struct ia64_ctx ia64_ctx;
@@ -44,6 +47,25 @@
 {
 }
 
+/* 
+ * When the context counter wraps around all TLBs need to be flushed because
+ * an old context number might have been reused. This is signalled by a bit
+ * set in ia64_ctx.flush, which is checked in the routine below. Called by
+ * activate_mm().                                        <efocht@ess.nec.de>
+ */
+static inline void
+delayed_tlb_flush (void)
+{
+	extern void __flush_tlb_all (void);
+
+	if (unlikely(ia64_ctx.flush & (1<<smp_processor_id()))) {
+		spin_lock(&ia64_ctx.lock);
+		__flush_tlb_all();
+		ia64_ctx.flush &= ~(1<<smp_processor_id());
+		spin_unlock(&ia64_ctx.lock);
+	}
+}
+
 static inline void
 get_new_mmu_context (struct mm_struct *mm)
 {
@@ -113,11 +135,28 @@
 	 * We may get interrupts here, but that's OK because interrupt
 	 * handlers cannot touch user-space.
 	 */
+	delayed_tlb_flush();
 	ia64_set_kr(IA64_KR_PT_BASE, __pa(next->pgd));
 	get_mmu_context(next);
 	reload_context(next);
 }
 
+/*
+ * Needed for the O(1) MQ scheduler.
+ */
+#if MAX_PRIO >= 192
+# error update this function. */
+#endif
+
+static inline int sched_find_first_bit(unsigned long *b)
+{
+	if (unlikely(b[0]))
+		return __ffs(b[0]);
+	if (b[1])
+		return 64 + __ffs(b[1]);
+	return __ffs(b[2]) + 128;
+}
+
 #define switch_mm(prev_mm,next_mm,next_task,cpu)	activate_mm(prev_mm, next_mm)
 
 # endif /* ! __ASSEMBLY__ */
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/pgalloc.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/pgalloc.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/pgalloc.h	Tue Feb  5 15:33:18 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/pgalloc.h	Fri Feb  8 12:11:24 2002
@@ -160,9 +160,12 @@
 
 #ifdef CONFIG_SMP
   extern void smp_flush_tlb_all (void);
+  extern void smp_flush_tlb_all_nowait (void);
 # define flush_tlb_all()	smp_flush_tlb_all()
+# define flush_tlb_all_nowait()	smp_flush_tlb_all_nowait()
 #else
 # define flush_tlb_all()	__flush_tlb_all()
+# define flush_tlb_all_nowait()	__flush_tlb_all()
 #endif
 
 /*
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/smp.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/smp.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/smp.h	Fri Nov  9 23:26:17 2001
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/smp.h	Fri Feb  8 12:11:24 2002
@@ -27,7 +27,7 @@
 #define SMP_IRQ_REDIRECTION	(1 << 0)
 #define SMP_IPI_REDIRECTION	(1 << 1)
 
-#define smp_processor_id()	(current->processor)
+#define smp_processor_id()	(current->cpu)
 
 extern struct smp_boot_data {
 	int cpu_count;
@@ -48,6 +48,9 @@
 
 extern unsigned long ap_wakeup_vector;
 
+extern void smp_send_reschedule(int cpu);
+extern void smp_send_reschedule_all(void);
+
 /*
  * Function to map hard smp processor id to logical id.  Slow, so
  * don't use this in performance-critical code.
@@ -110,12 +113,6 @@
 
 #define NO_PROC_ID		0xffffffff	/* no processor magic marker */
 
-/*
- * Extra overhead to move a task from one cpu to another (due to TLB and cache misses).
- * Expressed in "negative nice value" units (larger number means higher priority/penalty).
- */
-#define PROC_CHANGE_PENALTY	20
-
 extern void __init init_smp_config (void);
 extern void smp_do_timer (struct pt_regs *regs);
 
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/spinlock.h 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/spinlock.h
--- 2.4.17-ia64-kdbv2.1-K3/include/asm-ia64/spinlock.h	Mon Feb  4 12:41:39 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/asm-ia64/spinlock.h	Fri Feb  8 12:11:24 2002
@@ -84,7 +84,7 @@
 	"mov r29 = 1\n"						\
 	";;\n"							\
 	"1:\n"							\
-	"ld4.bias r2 = [%0]\n"					\
+	"ld4 r2 = [%0]\n"					\
 	";;\n"							\
 	"cmp4.eq p0,p7 = r0,r2\n"				\
 	"(p7) br.cond.spnt.few 1b \n"				\
diff -urN 2.4.17-ia64-kdbv2.1-K3/include/linux/smp.h 2.4.17-ia64-kdbv2.1-K3ia64/include/linux/smp.h
--- 2.4.17-ia64-kdbv2.1-K3/include/linux/smp.h	Fri Feb  8 12:02:06 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/include/linux/smp.h	Fri Feb  8 12:11:24 2002
@@ -24,12 +24,6 @@
 extern void smp_send_stop(void);
 
 /*
- * sends a 'reschedule' event to another CPU:
- */
-extern void FASTCALL(smp_send_reschedule(int cpu));
-
-
-/*
  * Boot processor call to load the other CPU's
  */
 extern void smp_boot_cpus(void);
diff -urN 2.4.17-ia64-kdbv2.1-K3/kdb/kdbmain.c 2.4.17-ia64-kdbv2.1-K3ia64/kdb/kdbmain.c
--- 2.4.17-ia64-kdbv2.1-K3/kdb/kdbmain.c	Mon Feb  4 12:41:04 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/kdb/kdbmain.c	Fri Feb  8 12:11:24 2002
@@ -2344,7 +2344,7 @@
 	for_each_task(p) {
 		kdb_printf("0x%p %08d %08d  %1.1d  %3.3d  %s  0x%p%c%s\n",
 			   (void *)p, p->pid, p->p_pptr->pid,
-			   task_has_cpu(p), p->processor,
+			   task_has_cpu(p), p->cpu,
 			   (p->state == 0)?"run ":(p->state>0)?"stop":"unrn",
 			   (void *)(&p->thread),
 			   (p == current) ? '*': ' ',
diff -urN 2.4.17-ia64-kdbv2.1-K3/kernel/printk.c 2.4.17-ia64-kdbv2.1-K3ia64/kernel/printk.c
--- 2.4.17-ia64-kdbv2.1-K3/kernel/printk.c	Fri Feb  8 12:02:06 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/kernel/printk.c	Fri Feb  8 12:11:24 2002
@@ -25,6 +25,8 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/interrupt.h>			/* For in_interrupt() */
+#include <linux/config.h>
+#include <linux/delay.h>
 
 #include <asm/uaccess.h>
 
diff -urN 2.4.17-ia64-kdbv2.1-K3/kernel/sched.c 2.4.17-ia64-kdbv2.1-K3ia64/kernel/sched.c
--- 2.4.17-ia64-kdbv2.1-K3/kernel/sched.c	Fri Feb  8 12:02:06 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/kernel/sched.c	Fri Feb  8 12:21:07 2002
@@ -154,6 +154,15 @@
 #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
 #define rt_task(p)		((p)->prio < MAX_RT_PRIO)
 
+/* needed on IA64, arch/ia64/kernel/head.S relies on it (EF) */
+struct task_struct * init_tasks[NR_CPUS] __initdata = {&init_task, };
+
+/* needed in kdb (EF) */
+int task_has_cpu(task_t *p)
+{
+	return (p == task_rq(p)->curr);
+}
+
 static inline runqueue_t *lock_task_rq(task_t *p, unsigned long *flags)
 {
 	struct runqueue *__rq;
@@ -671,7 +680,7 @@
 	task_t *p = current;
 
 	if (p == rq->idle) {
-		if (local_bh_count(cpu) || local_irq_count(cpu) > 1)
+		if (really_local_bh_count() || really_local_irq_count() > 1)
 			kstat.per_cpu_system[cpu] += system;
 #if CONFIG_SMP
 		idle_tick();
@@ -974,16 +983,16 @@
 
 	p->cpus_allowed = new_mask;
 	/*
-	 * Can the task run on the current CPU? If not then
+	 * Can the task run on its current CPU? If not then
 	 * migrate the process off to a proper CPU.
 	 */
-	if (new_mask & (1UL << smp_processor_id()))
+	if (new_mask & (1UL << p->cpu))
 		return;
 #if CONFIG_SMP
-	current->state = TASK_UNINTERRUPTIBLE;
-	smp_migrate_task(__ffs(new_mask), current);
-
-	schedule();
+	p->state = TASK_UNINTERRUPTIBLE;
+	smp_migrate_task(__ffs(new_mask), p);
+	if (p == current)
+		schedule();
 #endif
 }
 
@@ -1229,64 +1238,26 @@
 
 asmlinkage long sys_sched_yield(void)
 {
-	task_t *prev = current, *next;
 	runqueue_t *rq = this_rq();
 	prio_array_t *array;
-	list_t *queue;
-
-	if (unlikely(prev->state != TASK_RUNNING)) {
-		schedule();
-		return 0;
-	}
-	release_kernel_lock(prev, smp_processor_id());
-	prev->sleep_timestamp = jiffies;
-	/*
-	 * Decrease the yielding task's priority by one, to avoid
-	 * livelocks. This priority loss is temporary, it's recovered
-	 * once the current timeslice expires.
-	 *
-	 * If priority is already MAX_PRIO-1 then we still
-	 * roundrobin the task within the runlist.
-	 */
+ 
+       /*
+	* Decrease the yielding task's priority by one, to avoid
+	* livelocks. This priority loss is temporary, it's recovered
+	* once the current timeslice expires.
+	*
+	* If priority is already MAX_PRIO-1 then we still
+	* roundrobin the task within the runlist.
+	*/
 	spin_lock_irq(&rq->lock);
 	array = current->array;
-	/*
-	 * If the task has reached maximum priority (or is a RT task)
-	 * then just requeue the task to the end of the runqueue:
-	 */
-	if (likely(current->prio == MAX_PRIO-1 || rt_task(current))) {
-		list_del(&current->run_list);
-		list_add_tail(&current->run_list, array->queue + current->prio);
-	} else {
-		list_del(&current->run_list);
-		if (list_empty(array->queue + current->prio))
-			__clear_bit(current->prio, array->bitmap);
-		current->prio++;
-		list_add_tail(&current->run_list, array->queue + current->prio);
-		__set_bit(current->prio, array->bitmap);
-	}
-	/*
-	 * Context-switch manually. This is equivalent to
-	 * calling schedule(), but faster, because yield()
-	 * knows lots of things that can be optimized away
-	 * from the generic scheduler path:
-	 */
-	queue = array->queue + sched_find_first_bit(array->bitmap);
-	next = list_entry(queue->next, task_t, run_list);
-	prefetch(next);
-
-	prev->need_resched = 0;
-	if (likely(prev != next)) {
-		rq->nr_switches++;
-		rq->curr = next;
-		context_switch(prev, next);
-		barrier();
-		rq = this_rq();
-	}
+	dequeue_task(current, array);
+	if (likely(!rt_task(current)))
+		if (current->prio < MAX_PRIO-1)
+			current->prio++;
+	enqueue_task(current, array);
 	spin_unlock_irq(&rq->lock);
-
-	reacquire_kernel_lock(current);
-
+	schedule();
 	return 0;
 }
 
diff -urN 2.4.17-ia64-kdbv2.1-K3/kernel/timer.c 2.4.17-ia64-kdbv2.1-K3ia64/kernel/timer.c
--- 2.4.17-ia64-kdbv2.1-K3/kernel/timer.c	Fri Feb  8 12:02:06 2002
+++ 2.4.17-ia64-kdbv2.1-K3ia64/kernel/timer.c	Fri Feb  8 12:11:24 2002
@@ -584,18 +584,7 @@
 	int cpu = smp_processor_id(), system = user_tick ^ 1;
 
 	update_one_process(p, user_tick, system, cpu);
-	if (p->pid) {
-		if (--p->counter <= 0) {
-			p->counter = 0;
-			p->need_resched = 1;
-		}
-		if (p->nice > 0)
-			kstat.per_cpu_nice[cpu] += user_tick;
-		else
-			kstat.per_cpu_user[cpu] += user_tick;
-		kstat.per_cpu_system[cpu] += system;
-	} else if (really_local_bh_count() || really_local_irq_count() > 1)
-		kstat.per_cpu_system[cpu] += system;
+	scheduler_tick(user_tick, system);
 }
 
 /*