Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
new file mode 100644
index 0000000..c39ed70
--- /dev/null
+++ b/kernel/stop_machine.c
@@ -0,0 +1,212 @@
+#include <linux/stop_machine.h>
+#include <linux/kthread.h>
+#include <linux/sched.h>
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/syscalls.h>
+#include <asm/atomic.h>
+#include <asm/semaphore.h>
+#include <asm/uaccess.h>
+
+/* Since we effect priority and affinity (both of which are visible
+ * to, and settable by outside processes) we do indirection via a
+ * kthread. */
+
+/* Thread to stop each CPU in user context. */
+enum stopmachine_state {
+ STOPMACHINE_WAIT,
+ STOPMACHINE_PREPARE,
+ STOPMACHINE_DISABLE_IRQ,
+ STOPMACHINE_EXIT,
+};
+
+static enum stopmachine_state stopmachine_state;
+static unsigned int stopmachine_num_threads;
+static atomic_t stopmachine_thread_ack;
+static DECLARE_MUTEX(stopmachine_mutex);
+
+static int stopmachine(void *cpu)
+{
+ int irqs_disabled = 0;
+ int prepared = 0;
+
+ set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
+
+ /* Ack: we are alive */
+ mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
+ atomic_inc(&stopmachine_thread_ack);
+
+ /* Simple state machine */
+ while (stopmachine_state != STOPMACHINE_EXIT) {
+ if (stopmachine_state == STOPMACHINE_DISABLE_IRQ
+ && !irqs_disabled) {
+ local_irq_disable();
+ irqs_disabled = 1;
+ /* Ack: irqs disabled. */
+ mb(); /* Must read state first. */
+ atomic_inc(&stopmachine_thread_ack);
+ } else if (stopmachine_state == STOPMACHINE_PREPARE
+ && !prepared) {
+ /* Everyone is in place, hold CPU. */
+ preempt_disable();
+ prepared = 1;
+ mb(); /* Must read state first. */
+ atomic_inc(&stopmachine_thread_ack);
+ }
+ /* Yield in first stage: migration threads need to
+ * help our sisters onto their CPUs. */
+ if (!prepared && !irqs_disabled)
+ yield();
+ else
+ cpu_relax();
+ }
+
+ /* Ack: we are exiting. */
+ mb(); /* Must read state first. */
+ atomic_inc(&stopmachine_thread_ack);
+
+ if (irqs_disabled)
+ local_irq_enable();
+ if (prepared)
+ preempt_enable();
+
+ return 0;
+}
+
+/* Change the thread state */
+static void stopmachine_set_state(enum stopmachine_state state)
+{
+ atomic_set(&stopmachine_thread_ack, 0);
+ wmb();
+ stopmachine_state = state;
+ while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
+ cpu_relax();
+}
+
+static int stop_machine(void)
+{
+ int i, ret = 0;
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+ mm_segment_t old_fs = get_fs();
+
+ /* One high-prio thread per cpu. We'll do this one. */
+ set_fs(KERNEL_DS);
+ sys_sched_setscheduler(current->pid, SCHED_FIFO,
+ (struct sched_param __user *)¶m);
+ set_fs(old_fs);
+
+ atomic_set(&stopmachine_thread_ack, 0);
+ stopmachine_num_threads = 0;
+ stopmachine_state = STOPMACHINE_WAIT;
+
+ for_each_online_cpu(i) {
+ if (i == _smp_processor_id())
+ continue;
+ ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL);
+ if (ret < 0)
+ break;
+ stopmachine_num_threads++;
+ }
+
+ /* Wait for them all to come to life. */
+ while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
+ yield();
+
+ /* If some failed, kill them all. */
+ if (ret < 0) {
+ stopmachine_set_state(STOPMACHINE_EXIT);
+ up(&stopmachine_mutex);
+ return ret;
+ }
+
+ /* Don't schedule us away at this point, please. */
+ local_irq_disable();
+
+ /* Now they are all started, make them hold the CPUs, ready. */
+ stopmachine_set_state(STOPMACHINE_PREPARE);
+
+ /* Make them disable irqs. */
+ stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
+
+ return 0;
+}
+
+static void restart_machine(void)
+{
+ stopmachine_set_state(STOPMACHINE_EXIT);
+ local_irq_enable();
+}
+
+struct stop_machine_data
+{
+ int (*fn)(void *);
+ void *data;
+ struct completion done;
+};
+
+static int do_stop(void *_smdata)
+{
+ struct stop_machine_data *smdata = _smdata;
+ int ret;
+
+ ret = stop_machine();
+ if (ret == 0) {
+ ret = smdata->fn(smdata->data);
+ restart_machine();
+ }
+
+ /* We're done: you can kthread_stop us now */
+ complete(&smdata->done);
+
+ /* Wait for kthread_stop */
+ set_current_state(TASK_INTERRUPTIBLE);
+ while (!kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
+ __set_current_state(TASK_RUNNING);
+ return ret;
+}
+
+struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
+ unsigned int cpu)
+{
+ struct stop_machine_data smdata;
+ struct task_struct *p;
+
+ smdata.fn = fn;
+ smdata.data = data;
+ init_completion(&smdata.done);
+
+ down(&stopmachine_mutex);
+
+ /* If they don't care which CPU fn runs on, bind to any online one. */
+ if (cpu == NR_CPUS)
+ cpu = _smp_processor_id();
+
+ p = kthread_create(do_stop, &smdata, "kstopmachine");
+ if (!IS_ERR(p)) {
+ kthread_bind(p, cpu);
+ wake_up_process(p);
+ wait_for_completion(&smdata.done);
+ }
+ up(&stopmachine_mutex);
+ return p;
+}
+
+int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
+{
+ struct task_struct *p;
+ int ret;
+
+ /* No CPUs can come up or down during this. */
+ lock_cpu_hotplug();
+ p = __stop_machine_run(fn, data, cpu);
+ if (!IS_ERR(p))
+ ret = kthread_stop(p);
+ else
+ ret = PTR_ERR(p);
+ unlock_cpu_hotplug();
+
+ return ret;
+}
