diff -u --exclude-from /usr/src/exclude --new-file --recursive linux.20pre5/arch/i386/kernel/apm.c linux.20pre5-ac6/arch/i386/kernel/apm.c
--- linux.20pre5/arch/i386/kernel/apm.c	2002-08-29 18:39:52.000000000 +0100
+++ linux.20pre5-ac6/arch/i386/kernel/apm.c	2002-08-26 14:19:32.000000000 +0100
@@ -247,6 +247,7 @@
  *	    					powering off
  *	    [no-]debug			log some debugging messages
  *	    [no-]power[-_]off		power off on shutdown
+ *	    [no-]smp			Use apm even on an SMP box
  *	    bounce[-_]interval=<n>	number of ticks to ignore suspend
  *	    				bounces
  *          idle[-_]threshold=<n>       System idle percentage above which to
@@ -393,6 +394,7 @@
 static int			got_clock_diff;
 #endif
 static int			debug;
+static int			smp = 0;
 static int			apm_disabled = -1;
 #ifdef CONFIG_SMP
 static int			power_off;
@@ -494,6 +496,40 @@
 }
 
 /*
+ * Lock APM functionality to physical CPU 0
+ */
+ 
+#ifdef CONFIG_SMP
+
+static unsigned long apm_save_cpus(void)
+{
+	unsigned long x = current->cpus_allowed;
+	/* Some bioses don't like being called from CPU != 0 */
+	if (cpu_number_map(smp_processor_id()) != 0) {
+		set_cpus_allowed(current, 1 << cpu_logical_map(0));
+		if (unlikely(cpu_number_map(smp_processor_id()) != 0))
+			BUG();
+	}
+	return x;
+}
+
+static inline void apm_restore_cpus(unsigned long mask)
+{
+	set_cpus_allowed(current, mask);
+}
+
+#else
+
+/*
+ *	No CPU lockdown needed on a uniprocessor
+ */
+ 
+#define apm_save_cpus()	0
+#define apm_restore_cpus(x)	(void)(x)
+
+#endif
+
+/*
  * These are the actual BIOS calls.  Depending on APM_ZERO_SEGS and
  * apm_info.allow_ints, we are being really paranoid here!  Not only
  * are interrupts disabled, but all the segment registers (except SS)
@@ -566,7 +602,8 @@
 {
 	APM_DECL_SEGS
 	unsigned long	flags;
-
+	unsigned long cpus = apm_save_cpus();
+	
 	__save_flags(flags);
 	APM_DO_CLI;
 	APM_DO_SAVE_SEGS;
@@ -588,6 +625,9 @@
 		: "memory", "cc");
 	APM_DO_RESTORE_SEGS;
 	__restore_flags(flags);
+	
+	apm_restore_cpus(cpus);
+	
 	return *eax & 0xff;
 }
 
@@ -611,6 +651,8 @@
 	APM_DECL_SEGS
 	unsigned long	flags;
 
+	unsigned long cpus = apm_save_cpus();
+	
 	__save_flags(flags);
 	APM_DO_CLI;
 	APM_DO_SAVE_SEGS;
@@ -636,6 +678,9 @@
 	}
 	APM_DO_RESTORE_SEGS;
 	__restore_flags(flags);
+
+	apm_restore_cpus(cpus);
+	
 	return error;
 }
 
@@ -751,10 +796,12 @@
 	if (apm_bios_call_simple(APM_FUNC_IDLE, 0, 0, &eax)) {
 		static unsigned long t;
 
-		if (time_after(jiffies, t + 10 * HZ)) {
+		/* This always fails on some SMP boards running UP kernels.
+		 * Only report the failure the first 5 times.
+		 */
+		if (++t < 5) {
 			printk(KERN_DEBUG "apm_do_idle failed (%d)\n",
 					(eax >> 8) & 0xff);
-			t = jiffies;
 		}
 		return -1;
 	}
@@ -888,17 +935,12 @@
 	/*
 	 * This may be called on an SMP machine.
 	 */
-#ifdef CONFIG_SMP
-	/* Some bioses don't like being called from CPU != 0 */
-	if (cpu_number_map(smp_processor_id()) != 0) {
-		current->cpus_allowed = 1;
-		schedule();
-		if (unlikely(cpu_number_map(smp_processor_id()) != 0))
-			BUG();
-	}
-#endif
 	if (apm_info.realmode_power_off)
+	{
+		(void)apm_save_cpus();
 		machine_real_restart(po_bios_call, sizeof(po_bios_call));
+		/* Never returns */
+	}
 	else
 		(void) set_system_power_state(APM_STATE_OFF);
 }
@@ -1074,6 +1116,19 @@
 	}
 	if ((error == APM_SUCCESS) || (error == APM_NO_ERROR))
 		return 1;
+	if (error == APM_NOT_ENGAGED) {
+		static int tried;
+		int eng_error;
+		if (tried++ == 0) {
+			eng_error = apm_engage_power_management(APM_DEVICE_ALL, 1);
+			if (eng_error) {
+				apm_error("set display", error);
+				apm_error("engage interface", eng_error);
+				return 0;
+			} else
+				return apm_console_blank(blank);
+		}
+	}
 	apm_error("set display", error);
 	return 0;
 }
@@ -1571,7 +1626,7 @@
 
 	p = buf;
 
-	if ((smp_num_cpus == 1) &&
+	if ((smp_num_cpus == 1 || smp) &&
 	    !(error = apm_get_power_status(&bx, &cx, &dx))) {
 		ac_line_status = (bx >> 8) & 0xff;
 		battery_status = bx & 0xff;
@@ -1716,7 +1771,7 @@
 		}
 	}
 
-	if (debug) {
+	if (debug && (smp_num_cpus == 1 || smp )) {
 		error = apm_get_power_status(&bx, &cx, &dx);
 		if (error)
 			printk(KERN_INFO "apm: power status not available\n");
@@ -1760,7 +1815,7 @@
 		pm_power_off = apm_power_off;
 	register_sysrq_key('o', &sysrq_poweroff_op);
 
-	if (smp_num_cpus == 1) {
+	if (smp_num_cpus == 1 || smp) {
 #if defined(CONFIG_APM_DISPLAY_BLANK) && defined(CONFIG_VT)
 		console_blank_hook = apm_console_blank;
 #endif
@@ -1799,6 +1854,11 @@
 			str += 3;
 		if (strncmp(str, "debug", 5) == 0)
 			debug = !invert;
+		if (strncmp(str, "smp", 3) == 0)
+		{
+			smp = !invert;
+			idle_threshold = 100;
+		}
 		if ((strncmp(str, "power-off", 9) == 0) ||
 		    (strncmp(str, "power_off", 9) == 0))
 			power_off = !invert;
@@ -1903,7 +1963,7 @@
 		printk(KERN_NOTICE "apm: disabled on user request.\n");
 		return -ENODEV;
 	}
-	if ((smp_num_cpus > 1) && !power_off) {
+	if ((smp_num_cpus > 1) && !power_off && !smp) {
 		printk(KERN_NOTICE "apm: disabled - APM is not SMP safe.\n");
 		return -ENODEV;
 	}
@@ -1957,7 +2017,7 @@
 
 	kernel_thread(apm, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGHAND | SIGCHLD);
 
-	if (smp_num_cpus > 1) {
+	if (smp_num_cpus > 1 && !smp) {
 		printk(KERN_NOTICE
 		   "apm: disabled - APM is not SMP safe (power off active).\n");
 		return 0;
@@ -2025,5 +2085,8 @@
 MODULE_PARM(idle_period, "i");
 MODULE_PARM_DESC(idle_period,
 	"Period (in sec/100) over which to caculate the idle percentage");
+MODULE_PARM(smp, "i");
+MODULE_PARM_DESC(smp,
+	"Set this to enable APM use on an SMP platform. Use with caution on older systems");
 
 EXPORT_NO_SYMBOLS;