1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
From 19f56bcae5b8955b0882f0f63a2d0f916563fd39 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:30:27 -0500
Subject: [PATCH] stop_machine: convert stop_machine_run() to PREEMPT_RT
commit f9d9cfe4fa444b93238d7c3cf07af2dd85b151e8 in tip.
Instead of playing with non-preemption, introduce explicit
startup serialization. This is more robust and cleaner as
well.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
kernel/stop_machine.c | 26 +++++++++++++++++++++-----
1 files changed, 21 insertions(+), 5 deletions(-)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 9bb9fb1..72592cc 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -40,6 +40,8 @@ static atomic_t thread_ack;
static DEFINE_MUTEX(lock);
/* setup_lock protects refcount, stop_machine_wq and stop_machine_work. */
static DEFINE_MUTEX(setup_lock);
+/* do not start up until all worklets have been placed: */
+static DEFINE_MUTEX(startup_lock);
/* Users of stop_machine. */
static int refcount;
static struct workqueue_struct *stop_machine_wq;
@@ -71,6 +73,15 @@ static void stop_cpu(struct work_struct *unused)
int cpu = smp_processor_id();
int err;
+ /*
+ * Wait for the startup loop to finish:
+ */
+ mutex_lock(&startup_lock);
+ /*
+ * Let other threads continue too:
+ */
+ mutex_unlock(&startup_lock);
+
if (!active_cpus) {
if (cpu == cpumask_first(cpu_online_mask))
smdata = &active;
@@ -166,16 +177,21 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
set_state(STOPMACHINE_PREPARE);
- /* Schedule the stop_cpu work on all cpus: hold this CPU so one
- * doesn't hit this CPU until we're ready. */
- get_cpu();
+ /*
+ * Schedule the stop_cpu work on all cpus before allowing any
+ * of the CPUs to execute it:
+ */
+ mutex_lock(&startup_lock);
+
for_each_online_cpu(i) {
sm_work = per_cpu_ptr(stop_machine_work, i);
INIT_WORK(sm_work, stop_cpu);
queue_work_on(i, stop_machine_wq, sm_work);
}
- /* This will release the thread on our CPU. */
- put_cpu();
+
+ /* This will release the thread on all CPUs: */
+ mutex_unlock(&startup_lock);
+
flush_workqueue(stop_machine_wq);
ret = active.fnret;
mutex_unlock(&lock);
--
1.7.0.4
|
