Skip to content

Commit

Permalink
cpu/hotplug: Move online calls to hotplugged cpu
Browse files Browse the repository at this point in the history 
Let the hotplugged cpu invoke the setup/teardown callbacks
(CPU_ONLINE/CPU_DOWN_PREPARE) itself.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.536364371@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  • Loading branch information
Thomas Gleixner committed Mar 1, 2016
1 parent 4cb28ce commit 1cf4f62
Show file tree
Hide file tree
Showing 2 changed files with 102 additions and 52 deletions.
10 changes: 6 additions & 4 deletions include/linux/cpuhotplug.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,12 @@ enum cpuhp_state {
CPUHP_AP_ONLINE,
CPUHP_TEARDOWN_CPU,
CPUHP_CPU_SET_ACTIVE,
CPUHP_SMPBOOT_THREADS,
CPUHP_NOTIFY_ONLINE,
CPUHP_ONLINE_DYN,
CPUHP_ONLINE_DYN_END = CPUHP_ONLINE_DYN + 30,
CPUHP_KICK_AP_THREAD,
CPUHP_BP_ONLINE,
CPUHP_AP_SMPBOOT_THREADS,
CPUHP_AP_NOTIFY_ONLINE,
CPUHP_AP_ONLINE_DYN,
CPUHP_AP_ONLINE_DYN_END = CPUHP_AP_ONLINE_DYN + 30,
CPUHP_ONLINE,
};

Expand Down
144 changes: 96 additions & 48 deletions kernel/cpu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -429,7 +429,7 @@ static int cpuhp_should_run(unsigned int cpu)
/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
{
enum cpuhp_state target = max((int)st->target, CPUHP_AP_ONLINE);
enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);

return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
}
Expand Down Expand Up @@ -469,6 +469,9 @@ static void cpuhp_thread_fun(unsigned int cpu)
ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
}
} else {
/* Cannot happen .... */
BUG_ON(st->state < CPUHP_KICK_AP_THREAD);

/* Regular hotplug work */
if (st->state < st->target)
ret = cpuhp_ap_online(cpu, st);
Expand Down Expand Up @@ -502,12 +505,8 @@ static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
}

/* Regular hotplug invocation of the AP hotplug thread */
static int cpuhp_kick_ap_work(unsigned int cpu)
static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
enum cpuhp_state state = st->state;

trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
st->result = 0;
st->cb = NULL;
/*
Expand All @@ -517,6 +516,15 @@ static int cpuhp_kick_ap_work(unsigned int cpu)
smp_mb();
st->should_run = true;
wake_up_process(st->thread);
}

static int cpuhp_kick_ap_work(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
enum cpuhp_state state = st->state;

trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
__cpuhp_kick_ap_work(st);
wait_for_completion(&st->done);
trace_cpuhp_exit(cpu, st->state, state, st->result);
return st->result;
Expand Down Expand Up @@ -688,6 +696,9 @@ static int takedown_cpu(unsigned int cpu)
else
synchronize_rcu();

/* Park the hotplug thread */
kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);

/*
* Prevent irq alloc/free while the dying cpu reorganizes the
* interrupt affinities.
Expand Down Expand Up @@ -765,10 +776,34 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,

prev_state = st->state;
st->target = target;
/*
* If the current CPU state is in the range of the AP hotplug thread,
* then we need to kick the thread.
*/
if (st->state >= CPUHP_KICK_AP_THREAD) {
ret = cpuhp_kick_ap_work(cpu);
/*
* The AP side has done the error rollback already. Just
* return the error code..
*/
if (ret)
goto out;

/*
* We might have stopped still in the range of the AP hotplug
* thread. Nothing to do anymore.
*/
if (st->state >= CPUHP_KICK_AP_THREAD)
goto out;
}
/*
* The AP brought itself down below CPUHP_KICK_AP_THREAD. So we need
* to do the further cleanups.
*/
ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);

hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;

out:
cpu_hotplug_done();
/* This post dead nonsense must die */
if (!ret && hasdied)
Expand Down Expand Up @@ -828,10 +863,13 @@ void notify_cpu_starting(unsigned int cpu)
*/
static int cpuhp_set_cpu_active(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);

/* The cpu is marked online, set it active now */
set_cpu_active(cpu, true);
/* Unpark the stopper thread */
/* Unpark the stopper thread and the hotplug thread */
stop_machine_unpark(cpu);
kthread_unpark(st->thread);
return 0;
}

Expand Down Expand Up @@ -868,6 +906,26 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
cpuhp_tasks_frozen = tasks_frozen;

st->target = target;
/*
* If the current CPU state is in the range of the AP hotplug thread,
* then we need to kick the thread once more.
*/
if (st->state >= CPUHP_KICK_AP_THREAD) {
ret = cpuhp_kick_ap_work(cpu);
/*
* The AP side has done the error rollback already. Just
* return the error code..
*/
if (ret)
goto out;
}

/*
* Try to reach the target state. We max out on the BP at
* CPUHP_KICK_AP_THREAD. After that the AP hotplug thread is
* responsible for bringing it up to the target state.
*/
target = min((int)target, CPUHP_KICK_AP_THREAD);
ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
out:
cpu_hotplug_done();
Expand Down Expand Up @@ -1093,19 +1151,13 @@ static struct cpuhp_step cpuhp_bp_states[] = {
.startup = cpuhp_set_cpu_active,
.teardown = NULL,
},
[CPUHP_SMPBOOT_THREADS] = {
.name = "smpboot:threads",
.startup = smpboot_unpark_threads,
.teardown = smpboot_park_threads,
},
[CPUHP_NOTIFY_ONLINE] = {
.name = "notify:online",
.startup = notify_online,
.teardown = notify_down_prepare,
.cant_stop = true,
[CPUHP_KICK_AP_THREAD] = {
.name = "cpuhp:kickthread",
.startup = cpuhp_kick_ap_work,
.teardown = cpuhp_kick_ap_work,
},
#endif
[CPUHP_ONLINE] = {
[CPUHP_BP_ONLINE] = {
.name = "online",
.startup = NULL,
.teardown = NULL,
Expand All @@ -1122,6 +1174,16 @@ static struct cpuhp_step cpuhp_ap_states[] = {
.skip_onerr = true,
.cant_stop = true,
},
[CPUHP_AP_SMPBOOT_THREADS] = {
.name = "smpboot:threads",
.startup = smpboot_unpark_threads,
.teardown = smpboot_park_threads,
},
[CPUHP_AP_NOTIFY_ONLINE] = {
.name = "notify:online",
.startup = notify_online,
.teardown = notify_down_prepare,
},
#endif
[CPUHP_ONLINE] = {
.name = "online",
Expand All @@ -1140,7 +1202,9 @@ static int cpuhp_cb_check(enum cpuhp_state state)

static bool cpuhp_is_ap_state(enum cpuhp_state state)
{
return (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE);
if (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE)
return true;
return state > CPUHP_BP_ONLINE;
}

static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
Expand Down Expand Up @@ -1172,14 +1236,6 @@ static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
return cpuhp_get_step(state)->teardown;
}

/* Helper function to run callback on the target cpu */
static void cpuhp_on_cpu_cb(void *__cb)
{
int (*cb)(unsigned int cpu) = __cb;

BUG_ON(cb(smp_processor_id()));
}

/*
* Call the startup/teardown function for a step either on the AP or
* on the current CPU.
Expand All @@ -1191,26 +1247,18 @@ static int cpuhp_issue_call(int cpu, enum cpuhp_state state,

if (!cb)
return 0;

/*
* This invokes the callback directly for now. In a later step we
* convert that to use cpuhp_invoke_callback().
*/
if (cpuhp_is_ap_state(state)) {
/*
* Note, that a function called on the AP is not
* allowed to fail.
*/
if (cpu_online(cpu))
smp_call_function_single(cpu, cpuhp_on_cpu_cb, cb, 1);
return 0;
}

/*
* The non AP bound callbacks can fail on bringup. On teardown
* e.g. module removal we crash for now.
*/
ret = cb(cpu);
#ifdef CONFIG_SMP
if (cpuhp_is_ap_state(state))
ret = cpuhp_invoke_ap_callback(cpu, state, cb);
else
ret = cpuhp_invoke_callback(cpu, state, cb);
#else
ret = cpuhp_invoke_callback(cpu, state, cb);
#endif
BUG_ON(ret && !bringup);
return ret;
}
Expand Down Expand Up @@ -1252,11 +1300,11 @@ static int cpuhp_reserve_state(enum cpuhp_state state)
enum cpuhp_state i;

mutex_lock(&cpuhp_state_mutex);
for (i = CPUHP_ONLINE_DYN; i <= CPUHP_ONLINE_DYN_END; i++) {
if (cpuhp_bp_states[i].name)
for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
if (cpuhp_ap_states[i].name)
continue;

cpuhp_bp_states[i].name = "Reserved";
cpuhp_ap_states[i].name = "Reserved";
mutex_unlock(&cpuhp_state_mutex);
return i;
}
Expand Down Expand Up @@ -1289,7 +1337,7 @@ int __cpuhp_setup_state(enum cpuhp_state state,
get_online_cpus();

/* currently assignments for the ONLINE state are possible */
if (state == CPUHP_ONLINE_DYN) {
if (state == CPUHP_AP_ONLINE_DYN) {
dyn_state = 1;
ret = cpuhp_reserve_state(state);
if (ret < 0)
Expand Down

0 comments on commit 1cf4f62

Please sign in to comment.