Add hrtimer_start_on() support

This patch adds hrtimer_start_on(), which allows arming timers on
remote CPUs.  This is needed to avoided timer interrupts on "shielded"
CPUs and is also useful for implementing semi-partitioned schedulers.

3 files changed, 42 insertions, 1 deletions

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 02c2eff7478d..d810f5fea04f 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -947,6 +947,8 @@ apicinterrupt CALL_FUNCTION_VECTOR \
         call_function_interrupt smp_call_function_interrupt
 apicinterrupt RESCHEDULE_VECTOR \
         reschedule_interrupt smp_reschedule_interrupt
+apicinterrupt PULL_TIMERS_VECTOR \
+        pull_timers_interrupt smp_pull_timers_interrupt
 #endif
 
 apicinterrupt ERROR_APIC_VECTOR \
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index cd10a6437264..834496ed9536 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -115,6 +115,9 @@ static void __init smp_intr_init(void)
         alloc_intr_gate(CALL_FUNCTION_SINGLE_VECTOR,
                         call_function_single_interrupt);
 
+        /* IPI for hrtimer pulling on remote cpus */
+        alloc_intr_gate(PULL_TIMERS_VECTOR, pull_timers_interrupt);
+
         /* Low priority IPI to cleanup after moving an irq */
         set_intr_gate(IRQ_MOVE_CLEANUP_VECTOR, irq_move_cleanup_interrupt);
         set_bit(IRQ_MOVE_CLEANUP_VECTOR, used_vectors);
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index be8e1bde07aa..7ce9fb210d55 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -24,6 +24,8 @@
 #include <linux/cpu.h>
 #include <linux/gfp.h>
 
+#include <litmus/debug_trace.h>
+
 #include <asm/mtrr.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
@@ -164,6 +166,16 @@ static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
         return NMI_HANDLED;
 }
 
+/* trigger timers on remote cpu */
+void smp_send_pull_timers(int cpu)
+{
+        if (unlikely(cpu_is_offline(cpu))) {
+                WARN_ON(1);
+                return;
+        }
+        apic->send_IPI_mask(cpumask_of(cpu), PULL_TIMERS_VECTOR);
+}
+
 /*
  * this function calls the 'stop' function on all other CPUs in the system.
  */
@@ -216,7 +228,7 @@ static void native_stop_other_cpus(int wait)
                 while (num_online_cpus() > 1 && (wait || timeout--))
                         udelay(1);
         }
-        
+
         /* if the REBOOT_VECTOR didn't work, try with the NMI */
         if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi))  {
                 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
@@ -341,6 +353,30 @@ static int __init nonmi_ipi_setup(char *str)
 
 __setup("nonmi_ipi", nonmi_ipi_setup);
 
+extern void hrtimer_pull(void);
+
+static inline void __smp_pull_timers_interrupt(void)
+{
+        TRACE("pull timer interrupt\n");
+        hrtimer_pull();
+}
+
+__visible void smp_pull_timers_interrupt(struct pt_regs *regs)
+{
+        smp_entering_irq();
+        __smp_pull_timers_interrupt();
+        exiting_irq();
+}
+
+__visible void smp_trace_pull_timers_interrupt(struct pt_regs *regs)
+{
+        smp_entering_irq();
+        trace_call_function_single_entry(PULL_TIMERS_VECTOR);
+        __smp_pull_timers_interrupt();
+        trace_call_function_single_exit(PULL_TIMERS_VECTOR);
+        exiting_irq();
+}
+
 struct smp_ops smp_ops = {
         .smp_prepare_boot_cpu   = native_smp_prepare_boot_cpu,
         .smp_prepare_cpus       = native_smp_prepare_cpus,