| From: Thomas Gleixner <tglx@linutronix.de> |
| Date: Tue, 16 May 2017 20:42:32 +0200 |
| Subject: [PATCH 01/17] init: Pin init task to the boot CPU, initially |
| |
| Some of the boot code in init_kernel_freeable() which runs before SMP |
| bringup assumes (rightfully) that it runs on the boot CPU and therefore can |
| use smp_processor_id() in preemptible context. |
| |
| That works so far because the smp_processor_id() check starts to be |
| effective after smp bringup. That's just wrong. Starting with SMP bringup |
| and the ability to move threads around, smp_processor_id() in preemptible |
| context is broken. |
| |
| Aside of that it does not make sense to allow init to run on all CPUs |
| before sched_smp_init() has been run. |
| |
| Pin the init to the boot CPU so the existing code can continue to use |
| smp_processor_id() without triggering the checks when the enabling of those |
| checks starts earlier. |
| |
| Tested-by: Mark Rutland <mark.rutland@arm.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Steven Rostedt <rostedt@goodmis.org> |
| Link: http://lkml.kernel.org/r/20170516184734.943149935@linutronix.de |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| --- |
| init/main.c | 17 ++++++++++++----- |
| 1 file changed, 12 insertions(+), 5 deletions(-) |
| |
| --- a/init/main.c |
| +++ b/init/main.c |
| @@ -389,6 +389,7 @@ static __initdata DECLARE_COMPLETION(kth |
| |
| static noinline void __ref rest_init(void) |
| { |
| + struct task_struct *tsk; |
| int pid; |
| |
| rcu_scheduler_starting(); |
| @@ -397,7 +398,17 @@ static noinline void __ref rest_init(voi |
| * the init task will end up wanting to create kthreads, which, if |
| * we schedule it before we create kthreadd, will OOPS. |
| */ |
| - kernel_thread(kernel_init, NULL, CLONE_FS); |
| + pid = kernel_thread(kernel_init, NULL, CLONE_FS); |
| + /* |
| + * Pin init on the boot CPU. Task migration is not properly working |
| + * until sched_init_smp() has been run. It will set the allowed |
| + * CPUs for init to the non isolated CPUs. |
| + */ |
| + rcu_read_lock(); |
| + tsk = find_task_by_pid_ns(pid, &init_pid_ns); |
| + set_cpus_allowed_ptr(tsk, cpumask_of(smp_processor_id())); |
| + rcu_read_unlock(); |
| + |
| numa_default_policy(); |
| pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES); |
| rcu_read_lock(); |
| @@ -1011,10 +1022,6 @@ static noinline void __init kernel_init_ |
| * init can allocate pages on any node |
| */ |
| set_mems_allowed(node_states[N_MEMORY]); |
| - /* |
| - * init can run on any cpu. |
| - */ |
| - set_cpus_allowed_ptr(current, cpu_all_mask); |
| |
| cad_pid = task_pid(current); |
| |