Re: softirq buggy [Re: Serial port latency]

[Manfred Spraul <manfred@colorfullife.com>]

[-- Attachment #1: Type: text/plain, Size: 132 bytes --]

Pavel Machek wrote:
> 
> Ok. I was missing the fact it is checked on going userspace.
>

What about the attached patch?

--
	Manfred

[-- Attachment #2: patch-cpu-idle --]
[-- Type: text/plain, Size: 2858 bytes --]

// $Header$
// Kernel Version:
//  VERSION = 2
//  PATCHLEVEL = 4
//  SUBLEVEL = 3
//  EXTRAVERSION = -ac3
--- 2.4/include/linux/interrupt.h	Thu Feb 22 22:29:53 2001
+++ build-2.4/include/linux/interrupt.h	Sat Apr  7 23:51:31 2001
@@ -269,4 +269,25 @@
 extern int probe_irq_off(unsigned long);	/* returns 0 or negative on failure */
 extern unsigned int probe_irq_mask(unsigned long);	/* returns mask of ISA interrupts */
 
+/**
+ * cpu_is_idle - helper function for idle functions
+ * 
+ * pm_idle functions must call this function to verify that
+ * the cpu is really idle. It must be called with disabled
+ * local interrupts.
+ * Return values:
+ * 0: cpu was not idle.
+ * 1: go into power saving mode.
+ */
+static inline int cpu_is_idle(void)
+{
+	if (current->need_resched) {
+		return 0;
+	}
+	if (softirq_active(smp_processor_id()) & softirq_mask(smp_processor_id())) {
+		do_softirq();
+		return 0;
+	}
+	return 1;
+}
 #endif
--- 2.4/arch/i386/kernel/process.c	Thu Feb 22 22:28:52 2001
+++ build-2.4/arch/i386/kernel/process.c	Sat Apr  7 23:51:46 2001
@@ -73,6 +73,7 @@
 	hlt_counter--;
 }
 
+
 /*
  * We use this if we don't have any better
  * idle routine..
@@ -81,7 +82,7 @@
 {
 	if (current_cpu_data.hlt_works_ok && !hlt_counter) {
 		__cli();
-		if (!current->need_resched)
+		if (cpu_is_idle())
 			safe_halt();
 		else
 			__sti();
@@ -92,26 +93,21 @@
  * On SMP it's slightly faster (but much more power-consuming!)
  * to poll the ->need_resched flag instead of waiting for the
  * cross-CPU IPI to arrive. Use this option with caution.
+ *
+ * Isn't this identical to default_idle with the 'no-hlt' boot
+ * option? <manfred@colorfullife.com>
  */
 static void poll_idle (void)
 {
 	int oldval;
 
+	for(;;) {
+		if (!cpu_is_idle())
+			break;
+		__sti();
+		rep_nop();
+	}
 	__sti();
-
-	/*
-	 * Deal with another CPU just having chosen a thread to
-	 * run here:
-	 */
-	oldval = xchg(&current->need_resched, -1);
-
-	if (!oldval)
-		asm volatile(
-			"2:"
-			"cmpl $-1, %0;"
-			"rep; nop;"
-			"je 2b;"
-				: :"m" (current->need_resched));
 }
 
 /*
--- 2.4/drivers/acpi/cpu.c	Sat Apr  7 22:02:01 2001
+++ build-2.4/drivers/acpi/cpu.c	Sat Apr  7 23:55:17 2001
@@ -148,7 +148,7 @@
 		unsigned long diff;
 		
 		__cli();
-		if (current->need_resched)
+		if (!cpu_is_idle())
 			goto out;
 		if (acpi_bm_activity())
 			goto sleep2;
@@ -171,7 +171,7 @@
 		unsigned long diff;
 
 		__cli();
-		if (current->need_resched)
+		if (!cpu_is_idle())
 			goto out;
 		if (acpi_bm_activity())
 			goto sleep2;
@@ -205,7 +205,7 @@
 		unsigned long diff;
 
 		__cli();
-		if (current->need_resched)
+		if (!cpu_is_idle())
 			goto out;
 
 		time = acpi_read_pm_timer();
@@ -235,7 +235,7 @@
 		unsigned long diff;
 
 		__cli();
-		if (current->need_resched)
+		if (!cpu_is_idle())
 			goto out;
 		time = acpi_read_pm_timer();
 		acpi_c1_count++;