lkml.org 
[lkml]   [2020]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/2] lockdep: warn on redundant or incorrect irq state changes
Date
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@gmail.com>
---
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
\
 
 \ /
  Last update: 2020-07-23 12:56    [W:0.207 / U:1.784 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site