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: a0b0fd53e1e6 ("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

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 32406ef..35449f5 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -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
 }
 

diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 18d85ae..a525368 100644 (file)
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -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)