sched/core: Enable might_sleep() and smp_processor_id() checks early

might_sleep() and smp_processor_id() checks are enabled after the boot
process is done. That hides bugs in the SMP bringup and driver
initialization code.

Enable it right when the scheduler starts working, i.e. when init task and
kthreadd have been created and right before the idle task enables
preemption.

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>
Acked-by: Mark Rutland <mark.rutland@arm.com>
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/20170516184736.272225698@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/init/main.c b/init/main.c
index badae3bf08f1605bb87c3fdefcf4ea4893350ba3..df58a416dd1da54df4c3f2be807adb5366ec35b2 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -414,6 +414,16 @@ static noinline void __ref rest_init(void)
        rcu_read_lock();
        kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
        rcu_read_unlock();
+
+       /*
+        * Enable might_sleep() and smp_processor_id() checks.
+        * They cannot be enabled earlier because with CONFIG_PRREMPT=y
+        * kernel_thread() would trigger might_sleep() splats. With
+        * CONFIG_PREEMPT_VOLUNTARY=y the init task might have scheduled
+        * already, but it's stuck on the kthreadd_done completion.
+        */
+       system_state = SYSTEM_SCHEDULING;
+
        complete(&kthreadd_done);
 
        /*

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 877241e9f2b0daad807b55f056e69045010bd32d..c3e50cada84d8e38070857e619900f98b1b1da79 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6238,8 +6238,10 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
 
        if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
             !is_idle_task(current)) ||
-           system_state != SYSTEM_RUNNING || oops_in_progress)
+           system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
+           oops_in_progress)
                return;
+
        if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
                return;
        prev_jiffy = jiffies;

diff --git a/lib/smp_processor_id.c b/lib/smp_processor_id.c
index 690d75b132fa7cfdb41e2f6ae8fd6554db70e9b4..2fb007be02125a17f4c3b3345e656773d49209ae 100644 (file)
--- a/lib/smp_processor_id.c
+++ b/lib/smp_processor_id.c
@@ -28,7 +28,7 @@ notrace static unsigned int check_preemption_disabled(const char *what1,
        /*
         * It is valid to assume CPU-locality during early bootup:
         */
-       if (system_state != SYSTEM_RUNNING)
+       if (system_state < SYSTEM_SCHEDULING)
                goto out;
 
        /*