core-parking: interact with runtime SMT-disabling

When disabling SMT at runtime, secondary threads should no longer be
candidates for bringing back up in response to _PUR ACPI events. Purge
them from the tracking array.

Doing so involves adding locking to guard accounting data in the core
parking code. While adding the declaration for the lock, take the
liberty to drop two unnecessary forward function declarations.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c
index 50be0c722aaae968ea9a927f69066c47a1e464bf..3742ede61bdf3593b3660b6051a99a57350e105f 100644 (file)
--- a/xen/arch/x86/sysctl.c
+++ b/xen/arch/x86/sysctl.c
@@ -128,6 +128,9 @@ static long smt_up_down_helper(void *data)
         if ( !(x86_cpu_to_apicid[cpu] & sibling_mask) )
             continue;
 
+        if ( !up && core_parking_remove(cpu) )
+            continue;
+
         ret = up ? cpu_up_helper(_p(cpu))
                  : cpu_down_helper(_p(cpu));
 

diff --git a/xen/common/core_parking.c b/xen/common/core_parking.c
index c22710f94d57fa85d255a97e9caab33f8a54d22a..a6669e1766a8061b190b5c641ec57e10f31761dc 100644 (file)
--- a/xen/common/core_parking.c
+++ b/xen/common/core_parking.c
@@ -25,9 +25,7 @@
 #define CORE_PARKING_INCREMENT 1
 #define CORE_PARKING_DECREMENT 2
 
-static unsigned int core_parking_power(unsigned int event);
-static unsigned int core_parking_performance(unsigned int event);
-
+static DEFINE_SPINLOCK(accounting_lock);
 static uint32_t cur_idle_nums;
 static unsigned int core_parking_cpunum[NR_CPUS] = {[0 ... NR_CPUS-1] = -1};
 
@@ -100,10 +98,10 @@ static unsigned int core_parking_performance(unsigned int event)
     break;
 
     case CORE_PARKING_DECREMENT:
-    {
-        cpu = core_parking_cpunum[cur_idle_nums -1];
-    }
-    break;
+        spin_lock(&accounting_lock);
+        cpu = core_parking_cpunum[cur_idle_nums - 1];
+        spin_unlock(&accounting_lock);
+        break;
 
     default:
         break;
@@ -158,10 +156,10 @@ static unsigned int core_parking_power(unsigned int event)
     break;
 
     case CORE_PARKING_DECREMENT:
-    {
-        cpu = core_parking_cpunum[cur_idle_nums -1];
-    }
-    break;
+        spin_lock(&accounting_lock);
+        cpu = core_parking_cpunum[cur_idle_nums - 1];
+        spin_unlock(&accounting_lock);
+        break;
 
     default:
         break;
@@ -185,7 +183,11 @@ long core_parking_helper(void *data)
         ret = cpu_down(cpu);
         if ( ret )
             return ret;
+
+        spin_lock(&accounting_lock);
+        BUG_ON(cur_idle_nums >= ARRAY_SIZE(core_parking_cpunum));
         core_parking_cpunum[cur_idle_nums++] = cpu;
+        spin_unlock(&accounting_lock);
     }
 
     while ( cur_idle_nums > idle_nums )
@@ -194,12 +196,43 @@ long core_parking_helper(void *data)
         ret = cpu_up(cpu);
         if ( ret )
             return ret;
-        core_parking_cpunum[--cur_idle_nums] = -1;
+
+        if ( !core_parking_remove(cpu) )
+        {
+            ret = cpu_down(cpu);
+            if ( ret == -EEXIST )
+                ret = 0;
+            if ( ret )
+                break;
+        }
     }
 
     return ret;
 }
 
+bool core_parking_remove(unsigned int cpu)
+{
+    unsigned int i;
+    bool found = false;
+
+    spin_lock(&accounting_lock);
+
+    for ( i = 0; i < cur_idle_nums; ++i )
+        if ( core_parking_cpunum[i] == cpu )
+        {
+            found = true;
+            --cur_idle_nums;
+            break;
+        }
+
+    for ( ; i < cur_idle_nums; ++i )
+        core_parking_cpunum[i] = core_parking_cpunum[i + 1];
+
+    spin_unlock(&accounting_lock);
+
+    return found;
+}
+
 uint32_t get_cur_idle_nums(void)
 {
     return cur_idle_nums;

diff --git a/xen/include/asm-x86/smp.h b/xen/include/asm-x86/smp.h
index 9f533f90722714b08ff0b0f0b898041ad6254cf7..61446d0efd5042562886a2aa4a9a471b4e42bbe7 100644 (file)
--- a/xen/include/asm-x86/smp.h
+++ b/xen/include/asm-x86/smp.h
@@ -63,6 +63,7 @@ long cpu_up_helper(void *data);
 long cpu_down_helper(void *data);
 
 long core_parking_helper(void *data);
+bool core_parking_remove(unsigned int cpu);
 uint32_t get_cur_idle_nums(void);
 
 /*