From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 16 May 2017 20:42:32 +0200
Subject: init: Pin init task to the boot CPU, initially
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 29939274a9453c0489a62f21d999330c8ce3fe22
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension
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>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
init/main.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
--- a/init/main.c
+++ b/init/main.c
@@ -390,6 +390,7 @@ static __initdata DECLARE_COMPLETION(kth
noinline void __ref rest_init(void)
{
+ struct task_struct *tsk;
int pid;
rcu_scheduler_starting();
@@ -398,7 +399,17 @@ noinline void __ref rest_init(void)
* 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();
@@ -1043,10 +1054,6 @@ 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 = get_pid(task_pid(current));