Re: softirq buggy [Re: Serial port latency]

[Manfred Spraul]

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

What about the attached patch?

--
        Manfred
// $Header$
// 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? <[EMAIL PROTECTED]>
  */
 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++;