sched/core: Fix DEBUG_SPINLOCK annotation for rq->lock (269d5992) · Commits · 戴 / test

Mark noticed that he had sporadic "spinlock recursion" warnings from the DEBUG_SPINLOCK code. Now rq->lock is special in that the owner changes in the middle of a context switch. It so happens that we fix up the lock.owner too late, @prev can run (remotely) the moment prev->on_cpu is cleared, this then allows @prev to again try and acquire this rq->lock and trigger this warning. So we have to switch lock.owner before clearing prev->on_cpu. Do this by moving the DEBUG_SPINLOCK annotation from after switch_to() to before switch_to() and collect all lockdep annotations there into prepare_lock_switch() to mirror the existing finish_lock_switch(). Debugged-by:

Mark Rutland <mark.rutland@arm.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:

Mark Rutland <mark.rutland@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/core.c

+16 −11

Original line number	Diff line number	Diff line
		@@ -2601,19 +2601,31 @@ static inline void finish_task(struct task_struct *prev)
		#endif
		}

		static inline void finish_lock_switch(struct rq *rq)
		static inline void
		prepare_lock_switch(struct rq rq, struct task_struct next, struct rq_flags *rf)
		{
		/*
		* Since the runqueue lock will be released by the next
		* task (which is an invalid locking op but in the case
		* of the scheduler it's an obvious special-case), so we
		* do an early lockdep release here:
		*/
		rq_unpin_lock(rq, rf);
		spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
		#ifdef CONFIG_DEBUG_SPINLOCK
		/* this is a valid case when another task releases the spinlock */
		rq->lock.owner = current;
		rq->lock.owner = next;
		#endif
		}

		static inline void finish_lock_switch(struct rq *rq)
		{
		/*
		* If we are tracking spinlock dependencies then we have to
		* fix up the runqueue lock - which gets 'carried over' from
		* prev into current:
		*/
		spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);

		raw_spin_unlock_irq(&rq->lock);
		}

		@@ -2844,14 +2856,7 @@ context_switch(struct rq rq, struct task_struct prev,

		rq->clock_update_flags &= ~(RQCF_ACT_SKIP\|RQCF_REQ_SKIP);

		/*
		* Since the runqueue lock will be released by the next
		* task (which is an invalid locking op but in the case
		* of the scheduler it's an obvious special-case), so we
		* do an early lockdep release here:
		*/
		rq_unpin_lock(rq, rf);
		spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
		prepare_lock_switch(rq, next, rf);

		/* Here we just switch the register state and the stack. */
		switch_to(prev, next, prev);

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