Name: Check Calls to smp_processor_id()
Author: Rusty Russell
Status: Experimental

D: This patch inserts checks in smp_processor_id(), which doesn't have much
D: meaning when preemption is active.  It also includes various fixes for
D: the problems it finds.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/arch/i386/lib/delay.c working-2.6.0-smp_processor_id/arch/i386/lib/delay.c
--- linux-2.6.0/arch/i386/lib/delay.c	2003-09-22 10:23:08.000000000 +1000
+++ working-2.6.0-smp_processor_id/arch/i386/lib/delay.c	2003-12-23 23:20:30.000000000 +1100
@@ -31,10 +31,12 @@ void __delay(unsigned long loops)
 inline void __const_udelay(unsigned long xloops)
 {
 	int d0;
+	preempt_disable();
 	__asm__("mull %0"
 		:"=d" (xloops), "=&a" (d0)
 		:"1" (xloops),"0" (current_cpu_data.loops_per_jiffy));
         __delay(xloops * HZ);
+	preempt_enable();
 }
 
 void __udelay(unsigned long usecs)
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/include/asm-i386/smp.h working-2.6.0-smp_processor_id/include/asm-i386/smp.h
--- linux-2.6.0/include/asm-i386/smp.h	2003-09-22 10:28:12.000000000 +1000
+++ working-2.6.0-smp_processor_id/include/asm-i386/smp.h	2003-12-23 18:44:10.000000000 +1100
@@ -50,7 +50,7 @@ extern void zap_low_mappings (void);
  * from the initial startup. We map APIC_BASE very early in page_setup(),
  * so this is correct in the x86 case.
  */
-#define smp_processor_id() (current_thread_info()->cpu)
+#define __get_cpu() (current_thread_info()->cpu)
 
 extern cpumask_t cpu_callout_map;
 
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/include/linux/smp.h working-2.6.0-smp_processor_id/include/linux/smp.h
--- linux-2.6.0/include/linux/smp.h	2003-09-22 10:27:37.000000000 +1000
+++ working-2.6.0-smp_processor_id/include/linux/smp.h	2003-12-23 18:52:24.000000000 +1100
@@ -90,6 +90,13 @@ extern int smp_threads_ready;
  */
 void smp_prepare_boot_cpu(void);
 
+#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
+/* Far too hard to inline this: #include hell. */
+extern unsigned int smp_processor_id(void);
+#else
+#define smp_processor_id() __get_cpu()
+#endif /* CONFIG_DEBUG_SPINLOCK_SLEEP */
+
 #else /* !SMP */
 
 /*
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/kernel/module.c working-2.6.0-smp_processor_id/kernel/module.c
--- linux-2.6.0/kernel/module.c	2003-11-24 15:42:33.000000000 +1100
+++ working-2.6.0-smp_processor_id/kernel/module.c	2003-12-24 18:22:13.000000000 +1100
@@ -386,8 +386,8 @@ static void module_unload_init(struct mo
 	INIT_LIST_HEAD(&mod->modules_which_use_me);
 	for (i = 0; i < NR_CPUS; i++)
 		local_set(&mod->ref[i].count, 0);
-	/* Hold reference count during initialization. */
-	local_set(&mod->ref[smp_processor_id()].count, 1);
+	/* Hold reference count during initialization: who cares which one. */
+	local_set(&mod->ref[__get_cpu()].count, 1);
 	/* Backwards compatibility macros put refcount during init. */
 	mod->waiter = current;
 }
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/kernel/sched.c working-2.6.0-smp_processor_id/kernel/sched.c
--- linux-2.6.0/kernel/sched.c	2003-12-18 15:53:33.000000000 +1100
+++ working-2.6.0-smp_processor_id/kernel/sched.c	2003-12-24 18:21:58.000000000 +1100
@@ -2322,7 +2322,13 @@ EXPORT_SYMBOL(yield);
  */
 void io_schedule(void)
 {
-	struct runqueue *rq = this_rq();
+	/* This usage is actually OK if we get preempted, but suppress
+	 * warning --RR */
+	struct runqueue *rq;
+
+	preempt_disable();
+	rq = this_rq();
+	preempt_enable();
 
 	atomic_inc(&rq->nr_iowait);
 	schedule();
@@ -2867,6 +2873,26 @@ void __might_sleep(char *file, int line)
 #endif
 }
 EXPORT_SYMBOL(__might_sleep);
+
+unsigned int smp_processor_id(void)
+{
+	static int last;
+
+	if (system_running) {
+		preempt_disable();
+		if (preempt_count() == 1
+		    && !irqs_disabled()
+		    && cpus_weight(current->cpus_allowed) != 1
+		    && current != this_rq()->idle) {
+			WARN_ON(jiffies > last + HZ);
+			last = jiffies;
+		}
+		preempt_enable();
+	}
+	
+	return __get_cpu();
+}
+EXPORT_SYMBOL(smp_processor_id);
 #endif
 
 
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.6.0/kernel/softirq.c working-2.6.0-smp_processor_id/kernel/softirq.c
--- linux-2.6.0/kernel/softirq.c	2003-10-09 18:03:02.000000000 +1000
+++ working-2.6.0-smp_processor_id/kernel/softirq.c	2003-12-24 18:13:35.000000000 +1100
@@ -117,11 +117,11 @@ EXPORT_SYMBOL(do_softirq);
 
 void local_bh_enable(void)
 {
-	__local_bh_enable();
-	WARN_ON(irqs_disabled());
 	if (unlikely(!in_interrupt() &&
 		     local_softirq_pending()))
 		invoke_softirq();
+	__local_bh_enable();
+	WARN_ON(irqs_disabled());
 	preempt_check_resched();
 }
 EXPORT_SYMBOL(local_bh_enable);