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[Xen-changelog] [xen-unstable] Replace process_pending_timers() with process_pending_softirqs().



# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1261506934 0
# Node ID a60f508548a848ab7f92a5960dcc5df8e75f8c0f
# Parent  affb589507a7bea502ce7d0c8c3fa47ec9e4ff22
Replace process_pending_timers() with process_pending_softirqs().

This ensures that any critical softirqs are handled in a timely manner
(e.g., TIME_CALIBRATE_SOFTIRQ) while still avoiding being preempted by
the scheduler (by SCHEDULE_SOFTIRQ), which is the reason for avoiding
use of do_softirq() directly.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/acpi/cpu_idle.c |    2 +-
 xen/arch/x86/domain_build.c  |    6 +++---
 xen/arch/x86/smpboot.c       |    4 ++--
 xen/common/page_alloc.c      |    2 +-
 xen/common/softirq.c         |   16 ++++++++++++++--
 xen/common/timer.c           |    9 ---------
 xen/drivers/char/console.c   |    2 +-
 xen/include/xen/softirq.h    |    7 +++++++
 xen/include/xen/timer.h      |    6 ------
 9 files changed, 29 insertions(+), 25 deletions(-)

diff -r affb589507a7 -r a60f508548a8 xen/arch/x86/acpi/cpu_idle.c
--- a/xen/arch/x86/acpi/cpu_idle.c      Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/arch/x86/acpi/cpu_idle.c      Tue Dec 22 18:35:34 2009 +0000
@@ -230,7 +230,7 @@ static void acpi_processor_idle(void)
 
     sched_tick_suspend();
     /* sched_tick_suspend() can raise TIMER_SOFTIRQ. Process it now. */
-    process_pending_timers();
+    process_pending_softirqs();
 
     /*
      * Interrupts must be disabled during bus mastering calculations and
diff -r affb589507a7 -r a60f508548a8 xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c       Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/arch/x86/domain_build.c       Tue Dec 22 18:35:34 2009 +0000
@@ -924,7 +924,7 @@ int __init construct_dom0(
             ((unsigned int *)vphysmap_start)[pfn] = mfn;
         set_gpfn_from_mfn(mfn, pfn);
         if (!(pfn & 0xfffff))
-            process_pending_timers();
+            process_pending_softirqs();
     }
     si->first_p2m_pfn = pfn;
     si->nr_p2m_frames = d->tot_pages - count;
@@ -945,7 +945,7 @@ int __init construct_dom0(
             ++alloc_epfn;
 #endif
             if (!(pfn & 0xfffff))
-                process_pending_timers();
+                process_pending_softirqs();
         }
     }
     BUG_ON(pfn != d->tot_pages);
@@ -967,7 +967,7 @@ int __init construct_dom0(
 #undef pfn
             page++; pfn++;
             if (!(pfn & 0xfffff))
-                process_pending_timers();
+                process_pending_softirqs();
         }
     }
 
diff -r affb589507a7 -r a60f508548a8 xen/arch/x86/smpboot.c
--- a/xen/arch/x86/smpboot.c    Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/arch/x86/smpboot.c    Tue Dec 22 18:35:34 2009 +0000
@@ -1327,7 +1327,7 @@ void __cpu_die(unsigned int cpu)
                }
                mdelay(100);
                mb();
-               process_pending_timers();
+               process_pending_softirqs();
                if ((++i % 10) == 0)
                        printk(KERN_ERR "CPU %u still not dead...\n", cpu);
        }
@@ -1547,7 +1547,7 @@ int __devinit __cpu_up(unsigned int cpu)
        cpu_set(cpu, smp_commenced_mask);
        while (!cpu_isset(cpu, cpu_online_map)) {
                mb();
-               process_pending_timers();
+               process_pending_softirqs();
        }
 
        cpufreq_add_cpu(cpu);
diff -r affb589507a7 -r a60f508548a8 xen/common/page_alloc.c
--- a/xen/common/page_alloc.c   Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/common/page_alloc.c   Tue Dec 22 18:35:34 2009 +0000
@@ -893,7 +893,7 @@ void __init scrub_heap_pages(void)
 
     for ( mfn = first_valid_mfn; mfn < max_page; mfn++ )
     {
-        process_pending_timers();
+        process_pending_softirqs();
 
         pg = mfn_to_page(mfn);
 
diff -r affb589507a7 -r a60f508548a8 xen/common/softirq.c
--- a/xen/common/softirq.c      Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/common/softirq.c      Tue Dec 22 18:35:34 2009 +0000
@@ -22,7 +22,7 @@ irq_cpustat_t irq_stat[NR_CPUS];
 
 static softirq_handler softirq_handlers[NR_SOFTIRQS];
 
-asmlinkage void do_softirq(void)
+static void __do_softirq(unsigned long ignore_mask)
 {
     unsigned int i, cpu;
     unsigned long pending;
@@ -38,13 +38,25 @@ asmlinkage void do_softirq(void)
         if ( rcu_pending(cpu) )
             rcu_check_callbacks(cpu);
 
-        if ( (pending = softirq_pending(cpu)) == 0 )
+        if ( (pending = (softirq_pending(cpu) & ~ignore_mask)) == 0 )
             break;
 
         i = find_first_set_bit(pending);
         clear_bit(i, &softirq_pending(cpu));
         (*softirq_handlers[i])();
     }
+}
+
+void process_pending_softirqs(void)
+{
+    ASSERT(!in_irq() && local_irq_is_enabled());
+    /* Do not enter scheduler as it can preempt the calling context. */
+    __do_softirq(1ul<<SCHEDULE_SOFTIRQ);
+}
+
+asmlinkage void do_softirq(void)
+{
+    __do_softirq(0);
 }
 
 void open_softirq(int nr, softirq_handler handler)
diff -r affb589507a7 -r a60f508548a8 xen/common/timer.c
--- a/xen/common/timer.c        Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/common/timer.c        Tue Dec 22 18:35:34 2009 +0000
@@ -467,15 +467,6 @@ static void timer_softirq_action(void)
     spin_unlock_irq(&ts->lock);
 }
 
-
-void process_pending_timers(void)
-{
-    unsigned int cpu = smp_processor_id();
-    ASSERT(!in_irq() && local_irq_is_enabled());
-    if ( test_and_clear_bit(TIMER_SOFTIRQ, &softirq_pending(cpu)) )
-        timer_softirq_action();
-}
-
 s_time_t align_timer(s_time_t firsttick, uint64_t period)
 {
     if ( !period )
diff -r affb589507a7 -r a60f508548a8 xen/drivers/char/console.c
--- a/xen/drivers/char/console.c        Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/drivers/char/console.c        Tue Dec 22 18:35:34 2009 +0000
@@ -650,7 +650,7 @@ void __init console_endboot(void)
             printk("%d... ", 3-i);
             for ( j = 0; j < 100; j++ )
             {
-                process_pending_timers();
+                process_pending_softirqs();
                 mdelay(10);
             }
         }
diff -r affb589507a7 -r a60f508548a8 xen/include/xen/softirq.h
--- a/xen/include/xen/softirq.h Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/include/xen/softirq.h Tue Dec 22 18:35:34 2009 +0000
@@ -34,6 +34,13 @@ void raise_softirq(unsigned int nr);
 void raise_softirq(unsigned int nr);
 
 /*
+ * Process pending softirqs on this CPU. This should be called periodically
+ * when performing work that prevents softirqs from running in a timely manner.
+ * Use this instead of do_softirq() when you do not want to be preempted.
+ */
+void process_pending_softirqs(void);
+
+/*
  * TASKLETS -- dynamically-allocatable tasks run in softirq context
  * on at most one CPU at a time.
  */
diff -r affb589507a7 -r a60f508548a8 xen/include/xen/timer.h
--- a/xen/include/xen/timer.h   Tue Dec 22 18:18:07 2009 +0000
+++ b/xen/include/xen/timer.h   Tue Dec 22 18:35:34 2009 +0000
@@ -103,12 +103,6 @@ extern void kill_timer(struct timer *tim
 extern void kill_timer(struct timer *timer);
 
 /*
- * Process pending timers on this CPU. This should be called periodically
- * when performing work that prevents softirqs from running in a timely manner.
- */
-extern void process_pending_timers(void);
-
-/*
  * Bootstrap initialisation. Must be called before any other timer function.
  */
 extern void timer_init(void);

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