[tip: core/entry] sched: Detect call to schedule from critical entry code

[tip-bot2 for Frederic Weisbecker]

The following commit has been merged into the core/entry branch of tip:

Commit-ID:     9f68b5b74c48761bcbd7d90cf1426049bdbaabb7
Gitweb:        https://git.kernel.org/tip/9f68b5b74c48761bcbd7d90cf1426049bdbaabb7
Author:        Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate:    Tue, 17 Nov 2020 16:16:35 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 19 Nov 2020 11:25:42 +01:00

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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20201117151637.259084-4-frederic@xxxxxxxxxx
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7..c23d7cb 100644
--- 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));