Messages in this thread Patch in this message | | | From | Rusty Russell <> | Subject | Re: [PULL] module, param and stop_machine patches | Date | Sun, 26 Oct 2008 19:16:16 +1100 |
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On Sunday 26 October 2008 09:33:43 Linus Torvalds wrote: > On Sun, 26 Oct 2008, Rusty Russell wrote: > > Thanks, Heiko tracked this down; he's probably sleeping now but Hugh and > > Walt reported this fixes it for them and it makes sense. > > I'm not seeing any "tracked it down".
He tracked it down to moving init_workqueues() too early, so he moved that back.
> And it then mixes things up with 'stop_machine_init()' mess. Why does that > need to run so early?
The S/390 guys want to run it stop_machine v. early, so when Heiko introduced stop_machine_init() he made it an early_initcall().
> IOW, I don't think that patch is anything but a "hey, test if it works > with this". None of the changes or the problems are explained.
Indeed.
Turns out it's the cpu_online_map difference. If init_workqueues() is called too early, only the boot cpu is set. We then only create_workqueue_thread() for the boot cpu.
If CONFIG_HOTPLUG_CPU=y, it's fine since the hotplug callback will create the workqueue threads for the other cpus as they come up. Without it, the kevent workqueues on non-boot cpus don't get processed.
Still boots for me, but was a bit sick (varying, but no keyboard was one symptom).
> Nor do I see a sign-off from Heiko on it.
I thought mine would be sufficient since we both work for IBM?
> I also don't want to see more BUG_ON()'s there. Make them warnings or > something.
OK, I just killed them. It'll crash anyway.
Rusty.
Subject: Fix boot problems caused by moving init_workqueues() Date: Sat, 25 Oct 2008 16:16:22 +0200 From: Heiko Carstens <heiko.carstens@de.ibm.com>
The patch below moves the init_workqueues() call to its old place but makes the stop_machine initialization happen later (but still before core_initcalls).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> --- include/linux/stop_machine.h | 6 ++++++ init/main.c | 5 +++-- kernel/stop_machine.c | 9 ++++++--- 3 files changed, 15 insertions(+), 5 deletions(-)
diff -r 2b5f764088ee include/linux/stop_machine.h --- a/include/linux/stop_machine.h Sun Oct 26 18:50:23 2008 +1100 +++ b/include/linux/stop_machine.h Sun Oct 26 19:13:04 2008 +1100 @@ -35,6 +35,9 @@ int stop_machine(int (*fn)(void *), void * won't come or go while it's being called. Used by hotplug cpu. */ int __stop_machine(int (*fn)(void *), void *data, const cpumask_t *cpus); + +void stop_machine_init(void); + #else static inline int stop_machine(int (*fn)(void *), void *data, @@ -46,5 +49,8 @@ static inline int stop_machine(int (*fn) local_irq_enable(); return ret; } + +static inline void stop_machine_init(void) { } + #endif /* CONFIG_SMP */ #endif /* _LINUX_STOP_MACHINE */ diff -r 2b5f764088ee init/main.c --- a/init/main.c Sun Oct 26 18:50:23 2008 +1100 +++ b/init/main.c Sun Oct 26 19:13:04 2008 +1100 @@ -38,6 +38,7 @@ #include <linux/moduleparam.h> #include <linux/kallsyms.h> #include <linux/writeback.h> +#include <linux/stop_machine.h> #include <linux/cpu.h> #include <linux/cpuset.h> #include <linux/cgroup.h> @@ -767,6 +768,8 @@ static void __init do_basic_setup(void) static void __init do_basic_setup(void) { rcu_init_sched(); /* needed by module_init stage. */ + init_workqueues(); + stop_machine_init(); usermodehelper_init(); driver_init(); init_irq_proc(); @@ -850,8 +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 -r 2b5f764088ee kernel/stop_machine.c --- a/kernel/stop_machine.c Sun Oct 26 18:50:23 2008 +1100 +++ b/kernel/stop_machine.c Sun Oct 26 19:13:04 2008 +1100 @@ -154,10 +154,8 @@ int stop_machine(int (*fn)(void *), void } EXPORT_SYMBOL_GPL(stop_machine); -static int __init stop_machine_init(void) +void __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);
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