From 8afa3cc1e658920942f294a6297aed1b04f774f7 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 16 May 2017 20:42:48 +0200 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mark Rutland Cc: Greg Kroah-Hartman Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20170516184736.272225698@linutronix.de Signed-off-by: Ingo Molnar --- init/main.c | 10 ++++++++++ kernel/sched/core.c | 4 +++- lib/smp_processor_id.c | 2 +- 3 files changed, 14 insertions(+), 2 deletions(-) diff --git a/init/main.c b/init/main.c index badae3bf08f16..df58a416dd1da 100644 --- 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 877241e9f2b0d..c3e50cada84d8 100644 --- 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 690d75b132fa7..2fb007be02125 100644 --- 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; /* -- 2.39.5