linux-kernel - [PATCH 3/5] sched: Detect call to schedule from critical entry code

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Message-Id: <20201117151637.259084-4-frederic@kernel.org>
Date:   Tue, 17 Nov 2020 16:16:35 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Phil Auld <pauld@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [PATCH 3/5] 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@...nel.org>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Phil Auld <pauld@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d2003a7d5ab5..c23d7cb5aee3 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));
 
-- 
2.25.1