sched: Detect call to schedule from critical entry code

Detect calls to schedule() between user_enter() and user_exit(). Those
are symptoms of early entry code that either forgot to protect a call
to schedule() inside exception_enter()/exception_exit() or, in the case
of HAVE_CONTEXT_TRACKING_OFFSTACK, enabled interrupts or preemption in
a wrong spot.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201117151637.259084-4-frederic@kernel.org

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7d5ab558faf1a4fcac2937e8be6ed39c6a..c23d7cb5aee343eee15cd6b3a4f7c1d172250575 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4291,6 +4291,7 @@ static inline void schedule_debug(struct task_struct *prev, bool preempt)
                preempt_count_set(PREEMPT_DISABLED);
        }
        rcu_sleep_check();
+       SCHED_WARN_ON(ct_state() == CONTEXT_USER);
 
        profile_hit(SCHED_PROFILING, __builtin_return_address(0));