[tip: locking/core] lockdep: Fix usage_traceoverflow

tip-bot2 for Peter Zijlstra
2020-10-09T07:58:56Z

The following commit has been merged into the locking/core branch of tip:

Commit-ID: 2bb8945bcc1a768f2bc402a16c9610bba8d5187d
Gitweb: https://git.kernel.org/tip/2bb8945bcc1a768f2bc402a16c9610bba8d5187d
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 30 Sep 2020 11:49:37 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Fri, 09 Oct 2020 08:53:08 +02:00

lockdep: Fix usage_traceoverflow

Basically print_lock_class_header()'s for loop is out of sync with the
the size of of ->usage_traces[].

Also clean things up a bit while at it, to avoid such mishaps in the future.

Fixes: 23870f122768 ("locking/lockdep: Fix "USED" <- "IN-NMI" inversions")
Reported-by: Qian Cai <cai@redhat.com>
Debugged-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Qian Cai <cai@redhat.com>
Link: https://lkml.kernel.org/r/20200930094937.GE2651@hirez.programming.kicks-ass.net
---
include/linux/lockdep_types.h | 8 +++++--
kernel/locking/lockdep.c | 32 +++++++++++++----------------
kernel/locking/lockdep_internals.h | 7 ++++--
3 files changed, 26 insertions(+), 21 deletions(-)

diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index bb35b44..9a1fd49 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -35,8 +35,12 @@ enum lockdep_wait_type {
/*
* We'd rather not expose kernel/lockdep_states.h this wide, but we do need
* the total number of states... :-(
+ *
+ * XXX_LOCK_USAGE_STATES is the number of lines in lockdep_states.h, for each
+ * of those we generates 4 states, Additionally we report on USED and USED_READ.
*/
-#define XXX_LOCK_USAGE_STATES (1+2*4)
+#define XXX_LOCK_USAGE_STATES 2
+#define LOCK_TRACE_STATES (XXX_LOCK_USAGE_STATES*4 + 2)

/*
* NR_LOCKDEP_CACHING_CLASSES ... Number of classes
@@ -106,7 +110,7 @@ struct lock_class {
* IRQ/softirq usage tracking bits:
*/
unsigned long usage_mask;
- const struct lock_trace *usage_traces[XXX_LOCK_USAGE_STATES];
+ const struct lock_trace *usage_traces[LOCK_TRACE_STATES];

/*
* Generation counter, when doing certain classes of graph walking,
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2facbbd..a430fbb 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -585,6 +585,8 @@ static const char *usage_str[] =
#include "lockdep_states.h"
#undef LOCKDEP_STATE
[LOCK_USED] = "INITIAL USE",
+ [LOCK_USED_READ] = "INITIAL READ USE",
+ /* abused as string storage for verify_lock_unused() */
[LOCK_USAGE_STATES] = "IN-NMI",
};
#endif
@@ -1939,7 +1941,7 @@ static void print_lock_class_header(struct lock_class *class, int depth)
#endif
printk(KERN_CONT " {\n");

- for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
+ for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
if (class->usage_mask & (1 << bit)) {
int len = depth;

@@ -3969,7 +3971,7 @@ static int separate_irq_context(struct task_struct *curr,
static int mark_lock(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
- unsigned int old_mask, new_mask, ret = 1;
+ unsigned int new_mask, ret = 1;

if (new_bit >= LOCK_USAGE_STATES) {
DEBUG_LOCKS_WARN_ON(1);
@@ -3996,30 +3998,26 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
if (unlikely(hlock_class(this)->usage_mask & new_mask))
goto unlock;

- old_mask = hlock_class(this)->usage_mask;
hlock_class(this)->usage_mask |= new_mask;

- /*
- * Save one usage_traces[] entry and map both LOCK_USED and
- * LOCK_USED_READ onto the same entry.
- */
- if (new_bit == LOCK_USED || new_bit == LOCK_USED_READ) {
- if (old_mask & (LOCKF_USED | LOCKF_USED_READ))
- goto unlock;
- new_bit = LOCK_USED;
+ if (new_bit < LOCK_TRACE_STATES) {
+ if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
+ return 0;
}

- if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
- return 0;
-
switch (new_bit) {
+ case 0 ... LOCK_USED-1:
+ ret = mark_lock_irq(curr, this, new_bit);
+ if (!ret)
+ return 0;
+ break;
+
case LOCK_USED:
debug_atomic_dec(nr_unused_locks);
break;
+
default:
- ret = mark_lock_irq(curr, this, new_bit);
- if (!ret)
- return 0;
+ break;
}

unlock:
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index b0be156..de49f9e 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -20,9 +20,12 @@ enum lock_usage_bit {
#undef LOCKDEP_STATE
LOCK_USED,
LOCK_USED_READ,
- LOCK_USAGE_STATES
+ LOCK_USAGE_STATES,
};

+/* states after LOCK_USED_READ are not traced and printed */
+static_assert(LOCK_TRACE_STATES == LOCK_USAGE_STATES);
+
#define LOCK_USAGE_READ_MASK 1
#define LOCK_USAGE_DIR_MASK 2
#define LOCK_USAGE_STATE_MASK (~(LOCK_USAGE_READ_MASK | LOCK_USAGE_DIR_MASK))
@@ -121,7 +124,7 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ =
extern struct list_head all_lock_classes;
extern struct lock_chain lock_chains[];

-#define LOCK_USAGE_CHARS (1+LOCK_USAGE_STATES/2)
+#define LOCK_USAGE_CHARS (2*XXX_LOCK_USAGE_STATES + 1)

extern void get_usage_chars(struct lock_class *class,
char usage[LOCK_USAGE_CHARS]);