[Xen-changelog] [xen-unstable] stopmachine: Implement using tasklets rather than a softirq.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1271674079 -3600
# Node ID f1313dd68da4077ccd4f5530a7bc79d649bdffab
# Parent  652e40d4dd8864a16084a1ff634d95f4a7260f20
stopmachine: Implement using tasklets rather than a softirq.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/ia64/xen/domain.c |    4 ++++
 xen/arch/x86/domain.c      |    5 +++++
 xen/common/stop_machine.c  |   19 +++++++++++--------
 xen/include/xen/sched.h    |    3 +++
 xen/include/xen/softirq.h  |    1 -
 5 files changed, 23 insertions(+), 9 deletions(-)

diff -r 652e40d4dd88 -r f1313dd68da4 xen/arch/ia64/xen/domain.c
--- a/xen/arch/ia64/xen/domain.c        Mon Apr 19 11:34:49 2010 +0100
+++ b/xen/arch/ia64/xen/domain.c        Mon Apr 19 11:47:59 2010 +0100
@@ -2343,6 +2343,10 @@ void machine_halt(void)
        while(1);
 }
 
+void sync_local_execstate(void)
+{
+}
+
 void sync_vcpu_execstate(struct vcpu *v)
 {
 //     __ia64_save_fpu(v->arch._thread.fph);
diff -r 652e40d4dd88 -r f1313dd68da4 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c     Mon Apr 19 11:34:49 2010 +0100
+++ b/xen/arch/x86/domain.c     Mon Apr 19 11:47:59 2010 +0100
@@ -1509,6 +1509,11 @@ int __sync_lazy_execstate(void)
     return switch_required;
 }
 
+void sync_local_execstate(void)
+{
+    (void)__sync_lazy_execstate();
+}
+
 void sync_vcpu_execstate(struct vcpu *v)
 {
     if ( cpu_isset(smp_processor_id(), v->vcpu_dirty_cpumask) )
diff -r 652e40d4dd88 -r f1313dd68da4 xen/common/stop_machine.c
--- a/xen/common/stop_machine.c Mon Apr 19 11:34:49 2010 +0100
+++ b/xen/common/stop_machine.c Mon Apr 19 11:47:59 2010 +0100
@@ -24,7 +24,7 @@
 #include <xen/init.h>
 #include <xen/sched.h>
 #include <xen/spinlock.h>
-#include <xen/softirq.h>
+#include <xen/tasklet.h>
 #include <xen/stop_machine.h>
 #include <xen/errno.h>
 #include <xen/smp.h>
@@ -51,6 +51,7 @@ struct stopmachine_data {
     void *fn_data;
 };
 
+static DEFINE_PER_CPU(struct tasklet, stopmachine_tasklet);
 static struct stopmachine_data stopmachine_data;
 static DEFINE_SPINLOCK(stopmachine_lock);
 
@@ -81,10 +82,7 @@ int stop_machine_run(int (*fn)(void *), 
         return (*fn)(data);
     }
 
-    /* Note: We shouldn't spin on lock when it's held by others since others
-     * is expecting this cpus to enter softirq context. Or else deadlock
-     * is caused.
-     */
+    /* Must not spin here as the holder will expect us to be descheduled. */
     if ( !spin_trylock(&stopmachine_lock) )
         return -EBUSY;
 
@@ -98,8 +96,9 @@ int stop_machine_run(int (*fn)(void *), 
     smp_wmb();
 
     for_each_cpu_mask ( i, allbutself )
-        cpu_raise_softirq(i, STOPMACHINE_SOFTIRQ);
+        tasklet_schedule_on_cpu(&per_cpu(stopmachine_tasklet, i), i);
 
+    sync_local_execstate();
     stopmachine_set_state(STOPMACHINE_PREPARE);
 
     local_irq_disable();
@@ -118,10 +117,11 @@ int stop_machine_run(int (*fn)(void *), 
     return ret;
 }
 
-static void stopmachine_softirq(void)
+static void stopmachine_action(unsigned long unused)
 {
     enum stopmachine_state state = STOPMACHINE_START;
 
+    sync_local_execstate();
     smp_mb();
 
     while ( state != STOPMACHINE_EXIT )
@@ -153,7 +153,10 @@ static void stopmachine_softirq(void)
 
 static int __init cpu_stopmachine_init(void)
 {
-    open_softirq(STOPMACHINE_SOFTIRQ, stopmachine_softirq);
+    unsigned int cpu;
+    for_each_possible_cpu ( cpu )
+        tasklet_init(&per_cpu(stopmachine_tasklet, cpu),
+                     stopmachine_action, 0);
     return 0;
 }
 __initcall(cpu_stopmachine_init);
diff -r 652e40d4dd88 -r f1313dd68da4 xen/include/xen/sched.h
--- a/xen/include/xen/sched.h   Mon Apr 19 11:34:49 2010 +0100
+++ b/xen/include/xen/sched.h   Mon Apr 19 11:47:59 2010 +0100
@@ -480,6 +480,9 @@ void vcpu_sleep_sync(struct vcpu *d);
  */
 void sync_vcpu_execstate(struct vcpu *v);
 
+/* As above, for any lazy state being held on the local CPU. */
+void sync_local_execstate(void);
+
 /*
  * Called by the scheduler to switch to another VCPU. This function must
  * call context_saved(@prev) when the local CPU is no longer running in
diff -r 652e40d4dd88 -r f1313dd68da4 xen/include/xen/softirq.h
--- a/xen/include/xen/softirq.h Mon Apr 19 11:34:49 2010 +0100
+++ b/xen/include/xen/softirq.h Mon Apr 19 11:47:59 2010 +0100
@@ -8,7 +8,6 @@ enum {
     NEW_TLBFLUSH_CLOCK_PERIOD_SOFTIRQ,
     PAGE_SCRUB_SOFTIRQ,
     RCU_SOFTIRQ,
-    STOPMACHINE_SOFTIRQ,
     NR_COMMON_SOFTIRQS
 };
 

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