smpboot: Provide infrastructure for percpu hotplug threads

Provide a generic interface for setting up and tearing down percpu
threads.

On registration the threads for already online cpus are created and
started. On deregistration (modules) the threads are stoppped.

During hotplug operations the threads are created, started, parked and
unparked. The datastructure for registration provides a pointer to
percpu storage space and optional setup, cleanup, park, unpark
functions. These functions are called when the thread state changes.

Each implementation has to provide a function which is queried and
returns whether the thread should run and the thread function itself.

The core code handles all state transitions and avoids duplicated code
in the call sites.

[ paulmck: Preemption leak fix ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20120716103948.352501068@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 14d32588cccd..e615dfbcf794 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -280,12 +280,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
                                 __func__, cpu);
                 goto out_release;
         }
+        smpboot_park_threads(cpu);
 
         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
         if (err) {
                 /* CPU didn't die: tell everyone.  Can't complain. */
+                smpboot_unpark_threads(cpu);
                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
-
                 goto out_release;
         }
         BUG_ON(cpu_online(cpu));
@@ -354,6 +355,10 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
                 goto out;
         }
 
+        ret = smpboot_create_threads(cpu);
+        if (ret)
+                goto out;
+
         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
         if (ret) {
                 nr_calls--;
@@ -368,6 +373,9 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
                 goto out_notify;
         BUG_ON(!cpu_online(cpu));
 
+        /* Wake the per cpu threads */
+        smpboot_unpark_threads(cpu);
+
         /* Now call notifier in preparation. */
         cpu_notify(CPU_ONLINE | mod, hcpu);