[Xen-changelog] Sync against scheduler tail on other CPUs when context

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

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 1b7d6c2ae2f7626facde3dc61aa899204ada2da8
# Parent  6ce7c026320e4d27c4782168bfddbb10254b18c7
Sync against scheduler tail on other CPUs when context
switching to a new VCPU. Otherwise we cannot pull the 
VCPU's state off the other CPU.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 6ce7c026320e -r 1b7d6c2ae2f7 xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c     Mon Jan 16 23:54:24 2006
+++ b/xen/arch/x86/domain.c     Tue Jan 17 12:25:30 2006
@@ -738,8 +738,12 @@
     ASSERT(cpus_weight(dirty_mask) <= 1);
     if ( unlikely(!cpu_isset(cpu, dirty_mask) && !cpus_empty(dirty_mask)) )
     {
+        /* Make sure the next VCPU is not in a scheduling tail. */
+        while ( test_bit(_VCPUF_running, &next->vcpu_flags) )
+            cpu_relax();
         /* Other cpus call __sync_lazy_execstate from flush ipi handler. */
-        flush_tlb_mask(dirty_mask);
+        if ( !cpus_empty(next->vcpu_dirty_cpumask) )
+            flush_tlb_mask(next->vcpu_dirty_cpumask);
     }
 
     local_irq_disable();

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