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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: a0b0fd53e1 ("locking/lockdep: Free lock classes that are no longer in use")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200206152408.24165-2-longman@redhat.com
This commit is contained in:
Waiman Long 2020-02-06 10:24:03 -05:00 committed by Ingo Molnar
parent 0a679e13ea
commit b3b9c187dc
2 changed files with 29 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
kernel/locking/lockdep.c
View File

@ -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)
{
nr_process_chains++;
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
}

6
kernel/locking/lockdep_internals.h
View File

@ -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)