scheduler: sched_reschedule_on_cpu

kernel-src/include/kernel/scheduler.h

@@ -167,6 +167,7 @@ thread_t *sched_newthread(void *ip, size_t kstacksize, int priority, proc_t *pro
 void sched_destroyproc(proc_t *);
 void sched_destroythread(thread_t *);
 void sched_targetcpu(struct cpu_t *cpu);
+void sched_reschedule_on_cpu(struct cpu_t *cpu, bool target);
 void sched_sleepus(size_t us);
 void sched_apentry();
 void sched_inactiveproc(proc_t *proc);

kernel-src/sys/itimer.c

@@ -30,16 +30,11 @@ void itimer_pause(itimer_t *itimer, uintmax_t *remainingus, uintmax_t *repeatus)
 	bool intstatus = interrupt_set(false);
 	spinlock_acquire(&itimer->lock);
 
+
 	while (itimer->cpu && itimer->cpu != current_cpu()) {
 		// schedule on the itimer cpu
-		sched_targetcpu(itimer->cpu);
 		spinlock_release(&itimer->lock);
-		// allow interrupts to be handled (such as a tlb shootdown)
-		// as the other cpu could be busy waiting for this one
-		interrupt_set(true);
-		interrupt_set(false);
-		sched_yield();
-		sched_targetcpu(NULL);
+		sched_reschedule_on_cpu(itimer->cpu, false);
 		spinlock_acquire(&itimer->lock);
 	}
 

kernel-src/sys/scheduler.c

@@ -13,6 +13,7 @@
 #include <kernel/jobctl.h>
 #include <kernel/cmdline.h>
 #include <kernel/auth.h>
+#include <arch/smp.h>
 
 #define QUANTUM_US 100000
 #define SCHEDULER_STACK_SIZE PAGE_SIZE * 16
@@ -714,6 +715,52 @@ void sched_targetcpu(cpu_t *cpu) {
 	interrupt_set(intstatus);
 }
 
+// yields the current thread and sends an reschedule ipi to a specific cpu
+static void reschedule_yield(context_t *context, void *_cpu) {
+	thread_t *thread = current_thread();
+	cpu_t *cpu = _cpu;
+
+	spinlock_acquire(&runqueuelock);
+
+	thread_t *next = runqueuenext(0x0fffffff);
+
+	ARCH_CONTEXT_THREADSAVE(thread, context);
+
+	thread->flags &= ~SCHED_THREAD_FLAGS_RUNNING;
+	runqueueinsert(thread);
+
+	if (next == NULL)
+		next = current_cpu()->idlethread;
+
+	arch_smp_sendipi(cpu, cpu->reschedule_isr, ARCH_SMP_IPI_TARGET, false);
+
+	spinlock_release(&runqueuelock);
+	switchthread(next);
+}
+
+void sched_reschedule_on_cpu(cpu_t *cpu, bool target) {
+	cpu_t *old_target = current_thread()->cputarget;
+	current_thread()->cputarget = cpu;
+
+	bool status = interrupt_set(false);
+
+	// already on the cpu
+	if (cpu == current_cpu())
+		goto leave;
+
+	long old_priority = current_thread()->priority;
+	current_thread()->priority = 0;
+
+	arch_context_saveandcall(reschedule_yield, current_cpu()->schedulerstack, cpu);
+
+	current_thread()->priority = old_priority;
+
+	leave:
+	interrupt_set(status);
+	if (target == false)
+		current_thread()->cputarget = old_target;
+}
+
 static void timeout(context_t *, dpcarg_t arg) {
 	thread_t *thread = arg;
 	sched_wakeup(thread, 0);