From 378e8aa159caea08e869789ae40f73cea1480322 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@cloudius-systems.com>
Date: Sun, 3 Mar 2013 18:32:42 +0200
Subject: [PATCH] sched: preemption
Split the core scheduler into a function for calling from interrupts, and
a wrapper for calling it from normal paths. Call the preemptible path from
interrupt handlers.
---
arch/x64/exceptions.cc | 4 ++++
core/sched.cc | 42 ++++++++++++++++++++++++++++--------------
include/sched.hh | 2 ++
3 files changed, 34 insertions(+), 14 deletions(-)
diff --git a/arch/x64/exceptions.cc b/arch/x64/exceptions.cc
index d0351ce43..8ba6e909a 100644
--- a/arch/x64/exceptions.cc
+++ b/arch/x64/exceptions.cc
@@ -3,6 +3,7 @@
#include "processor.hh"
#include "interrupt.hh"
#include <boost/format.hpp>
+#include "sched.hh"
#include "debug.hh"
typedef boost::format fmt;
@@ -117,7 +118,10 @@ void interrupt(exception_frame* frame)
unsigned vector = frame->error_code;
idt.invoke_interrupt(vector);
processor::wrmsr(0x80b, 0); // EOI
+ // must call scheduler after EOI, or it may switch contexts and miss the EOI
current_interrupt_frame = nullptr;
+ // FIXME: layering violation
+ sched::preempt();
}
#define DUMMY_HANDLER(x) \
diff --git a/core/sched.cc b/core/sched.cc
index 51d4bf891..5656dd398 100644
--- a/core/sched.cc
+++ b/core/sched.cc
@@ -20,8 +20,6 @@ unsigned __thread preempt_counter;
elf::tls_data tls;
-// currently the scheduler will poll right after an interrupt, so no
-// need to do anything.
inter_processor_interrupt wakeup_ipi{[] {}};
}
@@ -44,23 +42,29 @@ void cpu::schedule(bool yield)
{
// FIXME: drive by IPI
handle_incoming_wakeups();
- thread* p = thread::current();
- if (p->_status.load() == thread::status::running && !yield) {
- return;
- }
with_lock(irq_lock, [this] {
- assert(!runqueue.empty());
- auto n = &runqueue.front();
- runqueue.pop_front();
- assert(n->_status.load() == thread::status::queued);
- n->_status.store(thread::status::running);
- if (n != thread::current()) {
- n->switch_to();
- }
+ reschedule_from_interrupt();
});
}
+void cpu::reschedule_from_interrupt()
+{
+ handle_incoming_wakeups();
+ thread* p = thread::current();
+ if (p->_status == thread::status::running) {
+ p->_status.store(thread::status::queued);
+ runqueue.push_back(*p);
+ }
+ auto n = &runqueue.front();
+ runqueue.pop_front();
+ assert(n->_status.load() == thread::status::queued);
+ n->_status.store(thread::status::running);
+ if (n != thread::current()) {
+ n->switch_to();
+ }
+}
+
void cpu::do_idle()
{
do {
@@ -261,6 +265,9 @@ void thread::wake()
// FIXME: warrant an interruption
if (_cpu != current()->tcpu()) {
wakeup_ipi.send(_cpu);
+ } else if (arch::irq_enabled()) {
+ _cpu->schedule();
+ // We'll also reschedule at the end of an interrupt if needed
}
}
@@ -355,6 +362,13 @@ void preempt_enable()
// FIXME: may need to schedule() here if a high prio thread is waiting
}
+void preempt()
+{
+ if (!preempt_counter) {
+ sched::cpu::current()->reschedule_from_interrupt();
+ }
+}
+
timer_list::callback_dispatch::callback_dispatch()
{
clock_event->set_callback(this);
diff --git a/include/sched.hh b/include/sched.hh
index db737a0f3..200413c72 100644
--- a/include/sched.hh
+++ b/include/sched.hh
@@ -266,8 +266,10 @@ struct cpu {
void do_idle();
void load_balance();
unsigned load();
+ void reschedule_from_interrupt();
};
+void preempt();
void preempt_disable();
void preempt_enable();
--
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