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cpu/hotplug: Add cpuhp_invoke_callback_range() 

Factorizing and unifying cpuhp callback range invocations, especially for
the hotunplug path, where two different ways of decrementing were used. The
first one, decrements before the callback is called:

 cpuhp_thread_fun()
     state = st->state;
     st->state--;
     cpuhp_invoke_callback(state);

The second one, after:

 take_down_cpu()|cpuhp_down_callbacks()
     cpuhp_invoke_callback(st->state);
     st->state--;

This is problematic for rolling back the steps in case of error, as
depending on the decrement, the rollback will start from N or N-1. It also
makes tracing inconsistent, between steps run in the cpuhp thread and
the others.

Additionally, avoid useless cpuhp_thread_fun() loops by skipping empty
steps.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210216103506.416286-4-vincent.donnefort@arm.com
This commit is contained in:
Vincent Donnefort 2021-02-16 10:35:06 +00:00 committed by Ingo Molnar
parent 62f2506940
commit 453e410851
1 changed files with 102 additions and 68 deletions
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170
kernel/cpu.c
View File

@ -135,6 +135,11 @@ static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
return cpuhp_hp_states + state;
}
static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
{
return bringup ? !step->startup.single : !step->teardown.single;
}
/**
* cpuhp_invoke_callback _ Invoke the callbacks for a given state
* @cpu: The cpu for which the callback should be invoked
@ -157,26 +162,24 @@ static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
if (st->fail == state) {
st->fail = CPUHP_INVALID;
if (!(bringup ? step->startup.single : step->teardown.single))
return 0;
return -EAGAIN;
}
if (cpuhp_step_empty(bringup, step)) {
WARN_ON_ONCE(1);
return 0;
}
if (!step->multi_instance) {
WARN_ON_ONCE(lastp && *lastp);
cb = bringup ? step->startup.single : step->teardown.single;
if (!cb)
return 0;
trace_cpuhp_enter(cpu, st->target, state, cb);
ret = cb(cpu);
trace_cpuhp_exit(cpu, st->state, state, ret);
return ret;
}
cbm = bringup ? step->startup.multi : step->teardown.multi;
if (!cbm)
return 0;
/* Single invocation for instance add/remove */
if (node) {
@ -475,6 +478,15 @@ cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
static inline void
cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
{
st->target = prev_state;
/*
* Already rolling back. No need invert the bringup value or to change
* the current state.
*/
if (st->rollback)
return;
st->rollback = true;
/*
@ -488,7 +500,6 @@ cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
st->state++;
}
st->target = prev_state;
st->bringup = !st->bringup;
}
@ -591,10 +602,53 @@ static int finish_cpu(unsigned int cpu)
* Hotplug state machine related functions
*/
static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
/*
* Get the next state to run. Empty ones will be skipped. Returns true if a
* state must be run.
*
* st->state will be modified ahead of time, to match state_to_run, as if it
* has already ran.
*/
static bool cpuhp_next_state(bool bringup,
enum cpuhp_state *state_to_run,
struct cpuhp_cpu_state *st,
enum cpuhp_state target)
{
for (st->state--; st->state > st->target; st->state--)
cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
do {
if (bringup) {
if (st->state >= target)
return false;
*state_to_run = ++st->state;
} else {
if (st->state <= target)
return false;
*state_to_run = st->state--;
}
if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
break;
} while (true);
return true;
}
static int cpuhp_invoke_callback_range(bool bringup,
unsigned int cpu,
struct cpuhp_cpu_state *st,
enum cpuhp_state target)
{
enum cpuhp_state state;
int err = 0;
while (cpuhp_next_state(bringup, &state, st, target)) {
err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
if (err)
break;
}
return err;
}
static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
@ -617,16 +671,12 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
enum cpuhp_state prev_state = st->state;
int ret = 0;
while (st->state < target) {
st->state++;
ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
if (ret) {
if (can_rollback_cpu(st)) {
st->target = prev_state;
undo_cpu_up(cpu, st);
}
break;
}
ret = cpuhp_invoke_callback_range(true, cpu, st, target);
if (ret) {
cpuhp_reset_state(st, prev_state);
if (can_rollback_cpu(st))
WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
prev_state));
}
return ret;
}
@ -690,17 +740,9 @@ static void cpuhp_thread_fun(unsigned int cpu)
state = st->cb_state;
st->should_run = false;
} else {
if (bringup) {
st->state++;
state = st->state;
st->should_run = (st->state < st->target);
WARN_ON_ONCE(st->state > st->target);
} else {
state = st->state;
st->state--;
st->should_run = (st->state > st->target);
WARN_ON_ONCE(st->state < st->target);
}
st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
if (!st->should_run)
goto end;
}
WARN_ON_ONCE(!cpuhp_is_ap_state(state));
@ -728,6 +770,7 @@ static void cpuhp_thread_fun(unsigned int cpu)
st->should_run = false;
}
end:
cpuhp_lock_release(bringup);
lockdep_release_cpus_lock();
@ -881,19 +924,18 @@ static int take_cpu_down(void *_param)
return err;
/*
* We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
* do this step again.
* Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
* down, that the current state is CPUHP_TEARDOWN_CPU - 1.
*/
WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
st->state--;
WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
/* Invoke the former CPU_DYING callbacks */
for (; st->state > target; st->state--) {
ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
/*
* DYING must not fail!
*/
WARN_ON_ONCE(ret);
}
ret = cpuhp_invoke_callback_range(false, cpu, st, target);
/*
* DYING must not fail!
*/
WARN_ON_ONCE(ret);
/* Give up timekeeping duties */
tick_handover_do_timer();
@ -975,27 +1017,22 @@ void cpuhp_report_idle_dead(void)
cpuhp_complete_idle_dead, st, 0);
}
static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
{
for (st->state++; st->state < st->target; st->state++)
cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
}
static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
enum cpuhp_state target)
{
enum cpuhp_state prev_state = st->state;
int ret = 0;
for (; st->state > target; st->state--) {
ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
if (ret) {
st->target = prev_state;
if (st->state < prev_state)
undo_cpu_down(cpu, st);
break;
}
ret = cpuhp_invoke_callback_range(false, cpu, st, target);
if (ret) {
cpuhp_reset_state(st, prev_state);
if (st->state < prev_state)
WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
prev_state));
}
return ret;
}
@ -1168,14 +1205,12 @@ void notify_cpu_starting(unsigned int cpu)
rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
cpumask_set_cpu(cpu, &cpus_booted_once_mask);
while (st->state < target) {
st->state++;
ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
/*
* STARTING must not fail!
*/
WARN_ON_ONCE(ret);
}
ret = cpuhp_invoke_callback_range(true, cpu, st, target);
/*
* STARTING must not fail!
*/
WARN_ON_ONCE(ret);
}
/*
@ -1781,8 +1816,7 @@ static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
* If there's nothing to do, we done.
* Relies on the union for multi_instance.
*/
if ((bringup && !sp->startup.single) ||
(!bringup && !sp->teardown.single))
if (cpuhp_step_empty(bringup, sp))
return 0;
/*
* The non AP bound callbacks can fail on bringup. On teardown