#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/smp.h>
+#include <linux/delay.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
put_online_cpus();
}
EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
+
+static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
+
+/*
+ * Called to poll specified CPU's state, for example, when waiting for
+ * a CPU to come online.
+ */
+int cpu_report_state(int cpu)
+{
+ return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+}
+
+/*
+ * If CPU has died properly, set its state to CPU_UP_PREPARE and
+ * return success. Otherwise, return -EBUSY if the CPU died after
+ * cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
+ * if cpu_wait_death() timed out and the CPU still hasn't gotten around
+ * to dying. In the latter two cases, the CPU might not be set up
+ * properly, but it is up to the arch-specific code to decide.
+ * Finally, -EIO indicates an unanticipated problem.
+ *
+ * Note that it is permissible to omit this call entirely, as is
+ * done in architectures that do no CPU-hotplug error checking.
+ */
+int cpu_check_up_prepare(int cpu)
+{
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
+ return 0;
+ }
+
+ switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
+
+ case CPU_POST_DEAD:
+
+ /* The CPU died properly, so just start it up again. */
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
+ return 0;
+
+ case CPU_DEAD_FROZEN:
+
+ /*
+ * Timeout during CPU death, so let caller know.
+ * The outgoing CPU completed its processing, but after
+ * cpu_wait_death() timed out and reported the error. The
+ * caller is free to proceed, in which case the state
+ * will be reset properly by cpu_set_state_online().
+ * Proceeding despite this -EBUSY return makes sense
+ * for systems where the outgoing CPUs take themselves
+ * offline, with no post-death manipulation required from
+ * a surviving CPU.
+ */
+ return -EBUSY;
+
+ case CPU_BROKEN:
+
+ /*
+ * The most likely reason we got here is that there was
+ * a timeout during CPU death, and the outgoing CPU never
+ * did complete its processing. This could happen on
+ * a virtualized system if the outgoing VCPU gets preempted
+ * for more than five seconds, and the user attempts to
+ * immediately online that same CPU. Trying again later
+ * might return -EBUSY above, hence -EAGAIN.
+ */
+ return -EAGAIN;
+
+ default:
+
+ /* Should not happen. Famous last words. */
+ return -EIO;
+ }
+}
+
+/*
+ * Mark the specified CPU online.
+ *
+ * Note that it is permissible to omit this call entirely, as is
+ * done in architectures that do no CPU-hotplug error checking.
+ */
+void cpu_set_state_online(int cpu)
+{
+ (void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Wait for the specified CPU to exit the idle loop and die.
+ */
+bool cpu_wait_death(unsigned int cpu, int seconds)
+{
+ int jf_left = seconds * HZ;
+ int oldstate;
+ bool ret = true;
+ int sleep_jf = 1;
+
+ might_sleep();
+
+ /* The outgoing CPU will normally get done quite quickly. */
+ if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
+ goto update_state;
+ udelay(5);
+
+ /* But if the outgoing CPU dawdles, wait increasingly long times. */
+ while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
+ schedule_timeout_uninterruptible(sleep_jf);
+ jf_left -= sleep_jf;
+ if (jf_left <= 0)
+ break;
+ sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
+ }
+update_state:
+ oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+ if (oldstate == CPU_DEAD) {
+ /* Outgoing CPU died normally, update state. */
+ smp_mb(); /* atomic_read() before update. */
+ atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
+ } else {
+ /* Outgoing CPU still hasn't died, set state accordingly. */
+ if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
+ oldstate, CPU_BROKEN) != oldstate)
+ goto update_state;
+ ret = false;
+ }
+ return ret;
+}
+
+/*
+ * Called by the outgoing CPU to report its successful death. Return
+ * false if this report follows the surviving CPU's timing out.
+ *
+ * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
+ * timed out. This approach allows architectures to omit calls to
+ * cpu_check_up_prepare() and cpu_set_state_online() without defeating
+ * the next cpu_wait_death()'s polling loop.
+ */
+bool cpu_report_death(void)
+{
+ int oldstate;
+ int newstate;
+ int cpu = smp_processor_id();
+
+ do {
+ oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
+ if (oldstate != CPU_BROKEN)
+ newstate = CPU_DEAD;
+ else
+ newstate = CPU_DEAD_FROZEN;
+ } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
+ oldstate, newstate) != oldstate);
+ return newstate == CPU_DEAD;
+}
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
projects / linux-2.6-block.git / blobdiff