Commit-ID: 5ebe7742fff8be5f1359bc50f5d43fb6ff7bd060
Gitweb: http://git.kernel.org/tip/5ebe7742fff8be5f1359bc50f5d43fb6ff7bd060
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 20 Sep 2017 19:00:19 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 25 Sep 2017 22:11:43 +0200
smp/hotplug: Differentiate the AP completion between up and down
With lockdep-crossrelease we get deadlock reports that span cpu-up and
cpu-down chains. Such deadlocks cannot possibly happen because cpu-up
and cpu-down are globally serialized.
takedown_cpu()
irq_lock_sparse()
wait_for_completion(&st->done)
cpuhp_thread_fun
cpuhp_up_callback
cpuhp_invoke_callback
irq_affinity_online_cpu
irq_local_spare()
irq_unlock_sparse()
complete(&st->done)
Now that we have consistent AP state, we can trivially separate the
AP completion between up and down using st->bringup.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: max.byungchul.park@xxxxxxxxx
Cc: bigeasy@xxxxxxxxxxxxx
Cc: efault@xxxxxx
Cc: rostedt@xxxxxxxxxxx
Link: https://lkml.kernel.org/r/20170920170546.872472799@xxxxxxxxxxxxx
---
kernel/cpu.c | 49 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 32 insertions(+), 17 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index d5c0998..6bbe261 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -46,7 +46,8 @@
* @bringup: Single callback bringup or teardown selector
* @cb_state: The state for a single callback (install/uninstall)
* @result: Result of the operation
- * @done: Signal completion to the issuer of the task
+ * @done_up: Signal completion to the issuer of the task for cpu-up
+ * @done_down: Signal completion to the issuer of the task for cpu-down
*/
struct cpuhp_cpu_state {
enum cpuhp_state state;
@@ -61,7 +62,8 @@ struct cpuhp_cpu_state {
struct hlist_node *last;
enum cpuhp_state cb_state;
int result;
- struct completion done;
+ struct completion done_up;
+ struct completion done_down;
#endif
};
@@ -130,14 +132,6 @@ static bool cpuhp_is_ap_state(enum cpuhp_state state)
return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
}
-/*
- * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
- */
-static bool cpuhp_is_atomic_state(enum cpuhp_state state)
-{
- return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
-}
-
static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
{
struct cpuhp_step *sp;
@@ -232,6 +226,26 @@ err:
}
#ifdef CONFIG_SMP
+static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+ struct completion *done = bringup ? &st->done_up : &st->done_down;
+ wait_for_completion(done);
+}
+
+static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
+{
+ struct completion *done = bringup ? &st->done_up : &st->done_down;
+ complete(done);
+}
+
+/*
+ * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
+ */
+static bool cpuhp_is_atomic_state(enum cpuhp_state state)
+{
+ return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
+}
+
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
static DEFINE_MUTEX(cpu_add_remove_lock);
bool cpuhp_tasks_frozen;
@@ -368,7 +382,7 @@ static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
smp_mb();
st->should_run = true;
wake_up_process(st->thread);
- wait_for_completion(&st->done);
+ wait_for_ap_thread(st, st->bringup);
}
static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
@@ -391,7 +405,7 @@ static int bringup_wait_for_ap(unsigned int cpu)
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
/* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
- wait_for_completion(&st->done);
+ wait_for_ap_thread(st, true);
if (WARN_ON_ONCE((!cpu_online(cpu))))
return -ECANCELED;
@@ -464,7 +478,8 @@ static void cpuhp_create(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
- init_completion(&st->done);
+ init_completion(&st->done_up);
+ init_completion(&st->done_down);
}
static int cpuhp_should_run(unsigned int cpu)
@@ -557,7 +572,7 @@ next:
cpuhp_lock_release(bringup);
if (!st->should_run)
- complete(&st->done);
+ complete_ap_thread(st, bringup);
}
/* Invoke a single callback on a remote cpu */
@@ -753,7 +768,7 @@ static int takedown_cpu(unsigned int cpu)
*
* Wait for the stop thread to go away.
*/
- wait_for_completion(&st->done);
+ wait_for_ap_thread(st, false);
BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
/* Interrupts are moved away from the dying cpu, reenable alloc/free */
@@ -772,7 +787,7 @@ static void cpuhp_complete_idle_dead(void *arg)
{
struct cpuhp_cpu_state *st = arg;
- complete(&st->done);
+ complete_ap_thread(st, false);
}
void cpuhp_report_idle_dead(void)
@@ -939,7 +954,7 @@ void cpuhp_online_idle(enum cpuhp_state state)
return;
st->state = CPUHP_AP_ONLINE_IDLE;
- complete(&st->done);
+ complete_ap_thread(st, true);
}
/* Requires cpu_add_remove_lock to be held */
--
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