Commit b3b9c187 authored by Waiman Long's avatar Waiman Long Committed by Ingo Molnar
Browse files

locking/lockdep: Decrement IRQ context counters when removing lock chain 



There are currently three counters to track the IRQ context of a lock
chain - nr_hardirq_chains, nr_softirq_chains and nr_process_chains.
They are incremented when a new lock chain is added, but they are
not decremented when a lock chain is removed. That causes some of the
statistic counts reported by /proc/lockdep_stats to be incorrect.
IRQ
Fix that by decrementing the right counter when a lock chain is removed.

Since inc_chains() no longer accesses hardirq_context and softirq_context
directly, it is moved out from the CONFIG_TRACE_IRQFLAGS conditional
compilation block.

Fixes: a0b0fd53 ("locking/lockdep: Free lock classes that are no longer in use")
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200206152408.24165-2-longman@redhat.com
parent 0a679e13

kernel/locking/lockdep.c

+23 −17
Original line number Diff line number Diff line
@@ -2298,18 +2298,6 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, 
	return 0;

}



static void inc_chains(void)

{

	if (current->hardirq_context)

		nr_hardirq_chains++;

	else {

		if (current->softirq_context)

			nr_softirq_chains++;

		else

			nr_process_chains++;

	}

}



#else



static inline int check_irq_usage(struct task_struct *curr,
@@ -2317,13 +2305,27 @@ static inline int check_irq_usage(struct task_struct *curr, 
{

	return 1;

}

#endif /* CONFIG_TRACE_IRQFLAGS */



static inline void inc_chains(void)

static void inc_chains(int irq_context)

{

	if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)

		nr_hardirq_chains++;

	else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)

		nr_softirq_chains++;

	else

		nr_process_chains++;

}



#endif /* CONFIG_TRACE_IRQFLAGS */

static void dec_chains(int irq_context)

{

	if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)

		nr_hardirq_chains--;

	else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)

		nr_softirq_chains--;

	else

		nr_process_chains--;

}



static void

print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
@@ -2843,7 +2845,7 @@ static inline int add_chain_cache(struct task_struct *curr, 


	hlist_add_head_rcu(&chain->entry, hash_head);

	debug_atomic_inc(chain_lookup_misses);

	inc_chains();

	inc_chains(chain->irq_context);



	return 1;

}
@@ -3596,7 +3598,8 @@ lock_used: 


static inline unsigned int task_irq_context(struct task_struct *task)

{

	return 2 * !!task->hardirq_context + !!task->softirq_context;

	return LOCK_CHAIN_HARDIRQ_CONTEXT * !!task->hardirq_context +

	       LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;

}



static int separate_irq_context(struct task_struct *curr,
@@ -4798,6 +4801,8 @@ recalc: 
		return;

	/* Overwrite the chain key for concurrent RCU readers. */

	WRITE_ONCE(chain->chain_key, chain_key);

	dec_chains(chain->irq_context);



	/*

	 * Note: calling hlist_del_rcu() from inside a

	 * hlist_for_each_entry_rcu() loop is safe.
@@ -4819,6 +4824,7 @@ recalc: 
	}

	*new_chain = *chain;

	hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key));

	inc_chains(new_chain->irq_context);

#endif

}

kernel/locking/lockdep_internals.h

+6 −0
Original line number Diff line number Diff line
@@ -106,6 +106,12 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ = 
#define STACK_TRACE_HASH_SIZE	16384

#endif



/*

 * Bit definitions for lock_chain.irq_context

 */

#define LOCK_CHAIN_SOFTIRQ_CONTEXT	(1 << 0)

#define LOCK_CHAIN_HARDIRQ_CONTEXT	(1 << 1)



#define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)



#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)

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