From 906a81a1c7717304436214fb09ba99e681c2db43 Mon Sep 17 00:00:00 2001
From: Tomas Hruby <tom@minix3.org>
Date: Wed, 15 Sep 2010 14:11:09 +0000
Subject: [PATCH] SMP - runctl() can stop across cpus

- if stopping a process that runs on a different CPU we tell the
  remote cpu to do that
---
 kernel/smp.c              | 44 +++++++++++++++++++++++++++++++++++----
 kernel/smp.h              |  1 +
 kernel/system/do_runctl.c | 11 +++++++++-
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index b11e0738c..77b6cede8 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -5,7 +5,17 @@ unsigned ncpus;
 unsigned ht_per_core;
 unsigned bsp_cpu_id;
 
-struct cpu cpus[CONFIG_MAX_CPUS];
+PUBLIC struct cpu cpus[CONFIG_MAX_CPUS];
+
+/* flags passed to another cpu along with a sched ipi */
+struct sched_ipi_data {
+	volatile u32_t	flags;
+	volatile u32_t	data;
+};
+
+PRIVATE struct sched_ipi_data  sched_ipi_data[CONFIG_MAX_CPUS];
+
+#define SCHED_IPI_STOP_PROC	1
 
 static volatile unsigned ap_cpus_booted;
 
@@ -36,18 +46,44 @@ PUBLIC void smp_ipi_halt_handler(void)
 
 PUBLIC void smp_schedule(unsigned cpu)
 {
+	/*
+	 * check if the cpu is processing some other ipi already. If yes, no
+	 * need to wake it up
+	 */
+	if ((volatile unsigned)sched_ipi_data[cpu].flags != 0)
+		return;
+	arch_send_smp_schedule_ipi(cpu);
+}
+
+PUBLIC void smp_schedule_stop_proc(struct proc * p)
+{
+	unsigned cpu = p->p_cpu;
+
+	sched_ipi_data[cpu].flags |= SCHED_IPI_STOP_PROC;
+	sched_ipi_data[cpu].data = (u32_t) p;
 	arch_send_smp_schedule_ipi(cpu);
+	BKL_UNLOCK();
+	while ((volatile unsigned)sched_ipi_data[cpu].flags != 0);
+	BKL_LOCK();
 }
 
 PUBLIC void smp_ipi_sched_handler(void)
 {
 	struct proc * p;
+	unsigned mycpu = cpuid;
+	unsigned flgs;
 	
 	ipi_ack();
 	
-	p = get_cpulocal_var(proc_ptr);
+	p = get_cpu_var(mycpu, proc_ptr);
+	flgs = sched_ipi_data[mycpu].flags;
 
-	if (p->p_endpoint != IDLE)
-		RTS_SET(p, RTS_PREEMPTED); /* calls dequeue() */
+	if (flgs & SCHED_IPI_STOP_PROC) {
+		RTS_SET((struct proc *)sched_ipi_data[mycpu].data, RTS_PROC_STOP);
+	}
+	else if (p->p_endpoint != IDLE) {
+		RTS_SET(p, RTS_PREEMPTED);
+	}
+	sched_ipi_data[cpuid].flags = 0;
 }
 
diff --git a/kernel/smp.h b/kernel/smp.h
index 0cb209d2e..408f166bb 100644
--- a/kernel/smp.h
+++ b/kernel/smp.h
@@ -59,6 +59,7 @@ _PROTOTYPE(void smp_ipi_halt_handler, (void));
 _PROTOTYPE(void smp_ipi_sched_handler, (void));
 
 _PROTOTYPE(void smp_schedule, (unsigned cpu));
+_PROTOTYPE(void smp_schedule_stop_proc, (struct proc * p));
 
 _PROTOTYPE(void arch_send_smp_schedule_ipi, (unsigned cpu));
 _PROTOTYPE(void arch_smp_halt_cpu, (void));
diff --git a/kernel/system/do_runctl.c b/kernel/system/do_runctl.c
index a724d01b4..3500f28f2 100644
--- a/kernel/system/do_runctl.c
+++ b/kernel/system/do_runctl.c
@@ -8,6 +8,7 @@
  */
 
 #include "kernel/system.h"
+#include <assert.h>
 
 #if USE_RUNCTL
 
@@ -51,7 +52,15 @@ PUBLIC int do_runctl(struct proc * caller, message * m_ptr)
   /* Either set or clear the stop flag. */
   switch (action) {
   case RC_STOP:
-	RTS_SET(rp, RTS_PROC_STOP);
+#if CONFIG_SMP
+	  /* check if we must stop a process on a different CPU */
+	  if (rp->p_cpu != cpuid) {
+		  smp_schedule_stop_proc(rp);
+		  assert(RTS_ISSET(rp, RTS_PROC_STOP));
+		  break;
+	  }
+#endif
+	  RTS_SET(rp, RTS_PROC_STOP);
 	break;
   case RC_RESUME:
 	RTS_UNSET(rp, RTS_PROC_STOP);
-- 
2.44.0