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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, jiangshanlai@gmail.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 1/6] sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled
Date: Tue,  5 Jan 2021 16:57:31 -0800
Message-ID: <20210106005736.12613-1-paulmck@kernel.org> (raw)
In-Reply-To: <20210106005713.GA12492@paulmck-ThinkPad-P72>

From: Peter Zijlstra <peterz@infradead.org>

The try_invoke_on_locked_down_task() function currently requires
that interrupts be enabled, but it is called with interrupts
disabled from rcu_print_task_stall(), resulting in an "IRQs not
enabled as expected" diagnostic.  This commit therefore updates
try_invoke_on_locked_down_task() to use raw_spin_lock_irqsave() instead
of raw_spin_lock_irq(), thus allowing use from either context.

Link: https://lore.kernel.org/lkml/000000000000903d5805ab908fc4@google.com/
Link: https://lore.kernel.org/lkml/20200928075729.GC2611@hirez.programming.kicks-ass.net/
Reported-by: syzbot+cb3b69ae80afd6535b0e@syzkaller.appspotmail.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/sched/core.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e7e4534..f768bb0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2989,7 +2989,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 
 /**
  * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
- * @p: Process for which the function is to be invoked.
+ * @p: Process for which the function is to be invoked, can be @current.
  * @func: Function to invoke.
  * @arg: Argument to function.
  *
@@ -3007,12 +3007,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
  */
 bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
 {
-	bool ret = false;
 	struct rq_flags rf;
+	bool ret = false;
 	struct rq *rq;
 
-	lockdep_assert_irqs_enabled();
-	raw_spin_lock_irq(&p->pi_lock);
+	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
 	if (p->on_rq) {
 		rq = __task_rq_lock(p, &rf);
 		if (task_rq(p) == rq)
@@ -3029,7 +3028,7 @@ bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct t
 				ret = func(p, arg);
 		}
 	}
-	raw_spin_unlock_irq(&p->pi_lock);
+	raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
 	return ret;
 }
 
-- 
2.9.5


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-06  0:57 [PATCH tip/core/rcu 0/6] Miscellaneous fixes for v5.12 Paul E. McKenney
2021-01-06  0:57 ` paulmck [this message]
2021-01-06  0:57 ` [PATCH tip/core/rcu 2/6] locking: Remove duplicate include of percpu-rwsem.h paulmck
2021-01-06  0:57 ` [PATCH tip/core/rcu 3/6] rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees paulmck
2021-01-06  0:57 ` [PATCH tip/core/rcu 4/6] rcu: Add lockdep_assert_irqs_disabled() to raw_spin_unlock_rcu_node() macros paulmck
2021-01-06  0:57 ` [PATCH tip/core/rcu 5/6] rcu-tasks: Add RCU-tasks self tests paulmck
2021-01-06  0:57 ` [PATCH tip/core/rcu 6/6] rcu: Make TASKS_TRACE_RCU select IRQ_WORK paulmck

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