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Date: Fri, 24 Oct 2008 21:44:14 +0200
From: Heiko Carstens <heiko.carstens@...ibm.com>
To: w41ter@...il.com
Cc: linux-kernel@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: commit a802dd0e breaks console keyboard input
On Fri, Oct 24, 2008 at 05:52:57AM -0700, w41ter@...il.com wrote:
> On Fri, 24 Oct 2008, Heiko Carstens wrote:
> > On Thu, Oct 23, 2008 at 05:09:24PM -0700, walt wrote:
> > > Hi team,
> > >
> > > commit a802dd0eb5fc97a50cf1abb1f788a8f6cc5db635
> > > Author: Heiko Carstens <heiko.carstens@...ibm.com>
> > > Date: Mon Oct 13 23:50:08 2008 +0200
> > >
> > > Call init_workqueues before pre smp initcalls.
> > >
> > > This commit causes the console login prompt to ignore my keystrokes
> > > so I'm unable to log in (though ssh works fine). Oddly, if I hit
> > > ctrl-alt-delete the machine does reboot, but no other keystrokes
> > > appear on the screen or have any effect that I can detect.
> > >
> > > No surprise that this problem appears only on my dual-core amd64
> > > machine, while the k7 single processor machine works normally.
> > >
> > > I've not seen anyone else complaining on the linux list, so maybe
> > > this is a BIOS bug on the affected machine? It's an ECS mobo with
> > > a GeForce6100PM-M2 chipset, and I use a ps/2 keyboard.
> >
> > Could you try the patch below and see if it makes any difference?
> > Thanks!
>
> <patch snipped for brevity>
>
> No difference that I can detect, sorry. The login prompt still
> ignores my keystrokes. I'm happy to try any other ideas or patches.
> (Yes, I did use git bisect to find this commit.)
Could you cc me on replies, please? Mails sent via vger.kernel.org reach
me with a lag of several hours.. so I might miss your reply. :)
Please try the patch below. It basically reverts the whole stop_machine
patches. That way we should know if it really comes from the moved init
call or if it is some other weird bug. I would have expected more bug
reports if the stop_machine patches would be broken. Hmmm...
diff -purN a/include/linux/workqueue.h b/include/linux/workqueue.h
--- a/include/linux/workqueue.h 2008-10-24 21:30:55.000000000 +0200
+++ b/include/linux/workqueue.h 2008-10-24 21:34:05.000000000 +0200
@@ -149,11 +149,11 @@ struct execute_work {
extern struct workqueue_struct *
__create_workqueue_key(const char *name, int singlethread,
- int freezeable, int rt, struct lock_class_key *key,
+ int freezeable, struct lock_class_key *key,
const char *lock_name);
#ifdef CONFIG_LOCKDEP
-#define __create_workqueue(name, singlethread, freezeable, rt) \
+#define __create_workqueue(name, singlethread, freezeable) \
({ \
static struct lock_class_key __key; \
const char *__lock_name; \
@@ -164,19 +164,17 @@ __create_workqueue_key(const char *name,
__lock_name = #name; \
\
__create_workqueue_key((name), (singlethread), \
- (freezeable), (rt), &__key, \
+ (freezeable), &__key, \
__lock_name); \
})
#else
-#define __create_workqueue(name, singlethread, freezeable, rt) \
- __create_workqueue_key((name), (singlethread), (freezeable), (rt), \
- NULL, NULL)
+#define __create_workqueue(name, singlethread, freezeable) \
+ __create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)
#endif
-#define create_workqueue(name) __create_workqueue((name), 0, 0, 0)
-#define create_rt_workqueue(name) __create_workqueue((name), 0, 0, 1)
-#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1, 0)
-#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0, 0)
+#define create_workqueue(name) __create_workqueue((name), 0, 0)
+#define create_freezeable_workqueue(name) __create_workqueue((name), 1, 1)
+#define create_singlethread_workqueue(name) __create_workqueue((name), 1, 0)
extern void destroy_workqueue(struct workqueue_struct *wq);
diff -purN a/init/main.c b/init/main.c
--- a/init/main.c 2008-10-24 21:30:55.000000000 +0200
+++ b/init/main.c 2008-10-24 21:34:09.000000000 +0200
@@ -768,6 +768,8 @@ static void __init do_initcalls(void)
static void __init do_basic_setup(void)
{
rcu_init_sched(); /* needed by module_init stage. */
+ /* drivers will send hotplug events */
+ init_workqueues();
usermodehelper_init();
driver_init();
init_irq_proc();
@@ -851,8 +853,6 @@ static int __init kernel_init(void * unu
cad_pid = task_pid(current);
- init_workqueues();
-
smp_prepare_cpus(setup_max_cpus);
do_pre_smp_initcalls();
diff -purN a/kernel/stop_machine.c b/kernel/stop_machine.c
--- a/kernel/stop_machine.c 2008-10-24 21:30:55.000000000 +0200
+++ b/kernel/stop_machine.c 2008-10-24 21:34:01.000000000 +0200
@@ -37,13 +37,9 @@ struct stop_machine_data {
/* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
static unsigned int num_threads;
static atomic_t thread_ack;
+static struct completion finished;
static DEFINE_MUTEX(lock);
-static struct workqueue_struct *stop_machine_wq;
-static struct stop_machine_data active, idle;
-static const cpumask_t *active_cpus;
-static void *stop_machine_work;
-
static void set_state(enum stopmachine_state newstate)
{
/* Reset ack counter. */
@@ -55,26 +51,21 @@ static void set_state(enum stopmachine_s
/* Last one to ack a state moves to the next state. */
static void ack_state(void)
{
- if (atomic_dec_and_test(&thread_ack))
- set_state(state + 1);
+ if (atomic_dec_and_test(&thread_ack)) {
+ /* If we're the last one to ack the EXIT, we're finished. */
+ if (state == STOPMACHINE_EXIT)
+ complete(&finished);
+ else
+ set_state(state + 1);
+ }
}
-/* This is the actual function which stops the CPU. It runs
- * in the context of a dedicated stopmachine workqueue. */
-static void stop_cpu(struct work_struct *unused)
+/* This is the actual thread which stops the CPU. It exits by itself rather
+ * than waiting for kthread_stop(), because it's easier for hotplug CPU. */
+static int stop_cpu(struct stop_machine_data *smdata)
{
enum stopmachine_state curstate = STOPMACHINE_NONE;
- struct stop_machine_data *smdata = &idle;
- int cpu = smp_processor_id();
- int err;
-
- if (!active_cpus) {
- if (cpu == first_cpu(cpu_online_map))
- smdata = &active;
- } else {
- if (cpu_isset(cpu, *active_cpus))
- smdata = &active;
- }
+
/* Simple state machine */
do {
/* Chill out and ensure we re-read stopmachine_state. */
@@ -87,11 +78,9 @@ static void stop_cpu(struct work_struct
hard_irq_disable();
break;
case STOPMACHINE_RUN:
- /* On multiple CPUs only a single error code
- * is needed to tell that something failed. */
- err = smdata->fn(smdata->data);
- if (err)
- smdata->fnret = err;
+ /* |= allows error detection if functions on
+ * multiple CPUs. */
+ smdata->fnret |= smdata->fn(smdata->data);
break;
default:
break;
@@ -101,6 +90,7 @@ static void stop_cpu(struct work_struct
} while (curstate != STOPMACHINE_EXIT);
local_irq_enable();
+ do_exit(0);
}
/* Callback for CPUs which aren't supposed to do anything. */
@@ -111,34 +101,78 @@ static int chill(void *unused)
int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
{
- struct work_struct *sm_work;
- int i;
+ int i, err;
+ struct stop_machine_data active, idle;
+ struct task_struct **threads;
- /* Set up initial state. */
- mutex_lock(&lock);
- num_threads = num_online_cpus();
- active_cpus = cpus;
active.fn = fn;
active.data = data;
active.fnret = 0;
idle.fn = chill;
idle.data = NULL;
+ /* This could be too big for stack on large machines. */
+ threads = kcalloc(NR_CPUS, sizeof(threads[0]), GFP_KERNEL);
+ if (!threads)
+ return -ENOMEM;
+
+ /* Set up initial state. */
+ mutex_lock(&lock);
+ init_completion(&finished);
+ num_threads = num_online_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();
for_each_online_cpu(i) {
- sm_work = percpu_ptr(stop_machine_work, i);
- INIT_WORK(sm_work, stop_cpu);
- queue_work_on(i, stop_machine_wq, sm_work);
+ struct stop_machine_data *smdata = &idle;
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+
+ if (!cpus) {
+ if (i == first_cpu(cpu_online_map))
+ smdata = &active;
+ } else {
+ if (cpu_isset(i, *cpus))
+ smdata = &active;
+ }
+
+ threads[i] = kthread_create((void *)stop_cpu, smdata, "kstop%u",
+ i);
+ if (IS_ERR(threads[i])) {
+ err = PTR_ERR(threads[i]);
+ threads[i] = NULL;
+ goto kill_threads;
+ }
+
+ /* Place it onto correct cpu. */
+ kthread_bind(threads[i], i);
+
+ /* Make it highest prio. */
+ if (sched_setscheduler_nocheck(threads[i], SCHED_FIFO, ¶m))
+ BUG();
}
+
+ /* We've created all the threads. Wake them all: hold this CPU so one
+ * doesn't hit this CPU until we're ready. */
+ get_cpu();
+ for_each_online_cpu(i)
+ wake_up_process(threads[i]);
+
/* This will release the thread on our CPU. */
put_cpu();
- flush_workqueue(stop_machine_wq);
+ wait_for_completion(&finished);
mutex_unlock(&lock);
+
+ kfree(threads);
+
return active.fnret;
+
+kill_threads:
+ for_each_online_cpu(i)
+ if (threads[i])
+ kthread_stop(threads[i]);
+ mutex_unlock(&lock);
+
+ kfree(threads);
+ return err;
}
int stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus)
@@ -153,11 +187,3 @@ int stop_machine(int (*fn)(void *), void
return ret;
}
EXPORT_SYMBOL_GPL(stop_machine);
-
-static int __init stop_machine_init(void)
-{
- stop_machine_wq = create_rt_workqueue("kstop");
- stop_machine_work = alloc_percpu(struct work_struct);
- return 0;
-}
-early_initcall(stop_machine_init);
diff -purN a/kernel/workqueue.c b/kernel/workqueue.c
--- a/kernel/workqueue.c 2008-10-24 21:30:55.000000000 +0200
+++ b/kernel/workqueue.c 2008-10-24 21:34:05.000000000 +0200
@@ -62,7 +62,6 @@ struct workqueue_struct {
const char *name;
int singlethread;
int freezeable; /* Freeze threads during suspend */
- int rt;
#ifdef CONFIG_LOCKDEP
struct lockdep_map lockdep_map;
#endif
@@ -767,7 +766,6 @@ init_cpu_workqueue(struct workqueue_stru
static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
{
- struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
struct workqueue_struct *wq = cwq->wq;
const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
struct task_struct *p;
@@ -783,8 +781,7 @@ static int create_workqueue_thread(struc
*/
if (IS_ERR(p))
return PTR_ERR(p);
- if (cwq->wq->rt)
- sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m);
+
cwq->thread = p;
return 0;
@@ -804,7 +801,6 @@ static void start_workqueue_thread(struc
struct workqueue_struct *__create_workqueue_key(const char *name,
int singlethread,
int freezeable,
- int rt,
struct lock_class_key *key,
const char *lock_name)
{
@@ -826,7 +822,6 @@ struct workqueue_struct *__create_workqu
lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
wq->singlethread = singlethread;
wq->freezeable = freezeable;
- wq->rt = rt;
INIT_LIST_HEAD(&wq->list);
if (singlethread) {
--
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