[PATCH 2/2] lockdep: warn on redundant or incorrect irq state changes
From: Nicholas Piggin
Date: Thu Jul 23 2020 - 06:56:34 EST
With the previous patch, lockdep hardirq state changes should not be
redundant. Softirq state changes already follow that pattern.
So warn on unexpected enable-when-enabled or disable-when-disabled
conditions, to catch possible errors or sloppy patterns that could
lead to similar bad behavior due to NMIs etc.
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
kernel/locking/lockdep.c | 80 +++++++++++++-----------------
kernel/locking/lockdep_internals.h | 4 --
kernel/locking/lockdep_proc.c | 10 +---
3 files changed, 35 insertions(+), 59 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 29a8de4c50b9..138458fb2234 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3649,15 +3649,8 @@ void lockdep_hardirqs_on_prepare(unsigned long ip)
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
- if (unlikely(current->hardirqs_enabled)) {
- /*
- * Neither irq nor preemption are disabled here
- * so this is racy by nature but losing one hit
- * in a stat is not a big deal.
- */
- __debug_atomic_inc(redundant_hardirqs_on);
+ if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled))
return;
- }
/*
* We're enabling irqs and according to our state above irqs weren't
@@ -3695,15 +3688,8 @@ void noinstr lockdep_hardirqs_on(unsigned long ip)
if (unlikely(!debug_locks || curr->lockdep_recursion))
return;
- if (curr->hardirqs_enabled) {
- /*
- * Neither irq nor preemption are disabled here
- * so this is racy by nature but losing one hit
- * in a stat is not a big deal.
- */
- __debug_atomic_inc(redundant_hardirqs_on);
+ if (DEBUG_LOCKS_WARN_ON(curr->hardirqs_enabled))
return;
- }
/*
* We're enabling irqs and according to our state above irqs weren't
@@ -3738,6 +3724,9 @@ void noinstr lockdep_hardirqs_off(unsigned long ip)
if (unlikely(!debug_locks || curr->lockdep_recursion))
return;
+ if (DEBUG_LOCKS_WARN_ON(!curr->hardirqs_enabled))
+ return;
+
/*
* So we're supposed to get called after you mask local IRQs, but for
* some reason the hardware doesn't quite think you did a proper job.
@@ -3745,17 +3734,13 @@ void noinstr lockdep_hardirqs_off(unsigned long ip)
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
- if (curr->hardirqs_enabled) {
- /*
- * We have done an ON -> OFF transition:
- */
- curr->hardirqs_enabled = 0;
- curr->hardirq_disable_ip = ip;
- curr->hardirq_disable_event = ++curr->irq_events;
- debug_atomic_inc(hardirqs_off_events);
- } else {
- debug_atomic_inc(redundant_hardirqs_off);
- }
+ /*
+ * We have done an ON -> OFF transition:
+ */
+ curr->hardirqs_enabled = 0;
+ curr->hardirq_disable_ip = ip;
+ curr->hardirq_disable_event = ++curr->irq_events;
+ debug_atomic_inc(hardirqs_off_events);
}
EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
@@ -3769,6 +3754,9 @@ void lockdep_softirqs_on(unsigned long ip)
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
+ if (DEBUG_LOCKS_WARN_ON(curr->softirqs_enabled))
+ return;
+
/*
* We fancy IRQs being disabled here, see softirq.c, avoids
* funny state and nesting things.
@@ -3776,11 +3764,6 @@ void lockdep_softirqs_on(unsigned long ip)
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
- if (curr->softirqs_enabled) {
- debug_atomic_inc(redundant_softirqs_on);
- return;
- }
-
current->lockdep_recursion++;
/*
* We'll do an OFF -> ON transition:
@@ -3809,26 +3792,26 @@ void lockdep_softirqs_off(unsigned long ip)
if (unlikely(!debug_locks || current->lockdep_recursion))
return;
+ if (DEBUG_LOCKS_WARN_ON(!curr->softirqs_enabled))
+ return;
+
/*
* We fancy IRQs being disabled here, see softirq.c
*/
if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
return;
- if (curr->softirqs_enabled) {
- /*
- * We have done an ON -> OFF transition:
- */
- curr->softirqs_enabled = 0;
- curr->softirq_disable_ip = ip;
- curr->softirq_disable_event = ++curr->irq_events;
- debug_atomic_inc(softirqs_off_events);
- /*
- * Whoops, we wanted softirqs off, so why aren't they?
- */
- DEBUG_LOCKS_WARN_ON(!softirq_count());
- } else
- debug_atomic_inc(redundant_softirqs_off);
+ /*
+ * We have done an ON -> OFF transition:
+ */
+ curr->softirqs_enabled = 0;
+ curr->softirq_disable_ip = ip;
+ curr->softirq_disable_event = ++curr->irq_events;
+ debug_atomic_inc(softirqs_off_events);
+ /*
+ * Whoops, we wanted softirqs off, so why aren't they?
+ */
+ DEBUG_LOCKS_WARN_ON(!softirq_count());
}
static int
@@ -5684,6 +5667,11 @@ void __init lockdep_init(void)
printk(" per task-struct memory footprint: %zu bytes\n",
sizeof(((struct task_struct *)NULL)->held_locks));
+
+ WARN_ON(irqs_disabled());
+
+ current->hardirqs_enabled = 1;
+ current->softirqs_enabled = 1;
}
static void
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index baca699b94e9..6dd8b1f06dc4 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -180,12 +180,8 @@ struct lockdep_stats {
unsigned int chain_lookup_misses;
unsigned long hardirqs_on_events;
unsigned long hardirqs_off_events;
- unsigned long redundant_hardirqs_on;
- unsigned long redundant_hardirqs_off;
unsigned long softirqs_on_events;
unsigned long softirqs_off_events;
- unsigned long redundant_softirqs_on;
- unsigned long redundant_softirqs_off;
int nr_unused_locks;
unsigned int nr_redundant_checks;
unsigned int nr_redundant;
diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 5525cd3ba0c8..98f204220ed9 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -172,12 +172,8 @@ static void lockdep_stats_debug_show(struct seq_file *m)
#ifdef CONFIG_DEBUG_LOCKDEP
unsigned long long hi1 = debug_atomic_read(hardirqs_on_events),
hi2 = debug_atomic_read(hardirqs_off_events),
- hr1 = debug_atomic_read(redundant_hardirqs_on),
- hr2 = debug_atomic_read(redundant_hardirqs_off),
si1 = debug_atomic_read(softirqs_on_events),
- si2 = debug_atomic_read(softirqs_off_events),
- sr1 = debug_atomic_read(redundant_softirqs_on),
- sr2 = debug_atomic_read(redundant_softirqs_off);
+ si2 = debug_atomic_read(softirqs_off_events);
seq_printf(m, " chain lookup misses: %11llu\n",
debug_atomic_read(chain_lookup_misses));
@@ -196,12 +192,8 @@ static void lockdep_stats_debug_show(struct seq_file *m)
seq_printf(m, " hardirq on events: %11llu\n", hi1);
seq_printf(m, " hardirq off events: %11llu\n", hi2);
- seq_printf(m, " redundant hardirq ons: %11llu\n", hr1);
- seq_printf(m, " redundant hardirq offs: %11llu\n", hr2);
seq_printf(m, " softirq on events: %11llu\n", si1);
seq_printf(m, " softirq off events: %11llu\n", si2);
- seq_printf(m, " redundant softirq ons: %11llu\n", sr1);
- seq_printf(m, " redundant softirq offs: %11llu\n", sr2);
#endif
}
--
2.23.0