2020-07-25 18:54:46

by Chris Wilson

Subject: [PATCH] locking/lockdep: Fix overflow in presentation of average lock-time

Though the number of lock-acquisitions is tracked as unsigned long, this
is passed as the divisor to div_s64() which interprets it as a s32,
giving nonsense values with more than 2 billion acquisitons. E.g.

acquisitions holdtime-min holdtime-max holdtime-total holdtime-avg
-------------------------------------------------------------------------
2350439395 0.07 353.38 649647067.36 0.-32

Signed-off-by: Chris Wilson <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Will Deacon <[email protected]>
---
kernel/locking/lockdep_proc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 5525cd3ba0c8..02ef87f50df2 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -423,7 +423,7 @@ static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
seq_time(m, lt->min);
seq_time(m, lt->max);
seq_time(m, lt->total);
- seq_time(m, lt->nr ? div_s64(lt->total, lt->nr) : 0);
+ seq_time(m, lt->nr ? div64_u64(lt->total, lt->nr) : 0);
}

static void seq_stats(struct seq_file *m, struct lock_stat_data *data)
--
2.20.1

2020-07-25 19:54:49

by tip-bot2 for Jacob Pan

Subject: [tip: locking/urgent] locking/lockdep: Fix overflow in presentation of average lock-time

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

Commit-ID: a7ef9b28aa8d72a1656fa6f0a01bbd1493886317
Gitweb: https://git.kernel.org/tip/a7ef9b28aa8d72a1656fa6f0a01bbd1493886317
Author: Chris Wilson <[email protected]>
AuthorDate: Sat, 25 Jul 2020 19:51:10 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Sat, 25 Jul 2020 21:47:42 +02:00

locking/lockdep: Fix overflow in presentation of average lock-time

Though the number of lock-acquisitions is tracked as unsigned long, this
is passed as the divisor to div_s64() which interprets it as a s32,
giving nonsense values with more than 2 billion acquisitons. E.g.

acquisitions holdtime-min holdtime-max holdtime-total holdtime-avg
-------------------------------------------------------------------------
2350439395 0.07 353.38 649647067.36 0.-32

Signed-off-by: Chris Wilson <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/locking/lockdep_proc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 5525cd3..02ef87f 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -423,7 +423,7 @@ static void seq_lock_time(struct seq_file *m, struct lock_time *lt)
seq_time(m, lt->min);
seq_time(m, lt->max);
seq_time(m, lt->total);
- seq_time(m, lt->nr ? div_s64(lt->total, lt->nr) : 0);
+ seq_time(m, lt->nr ? div64_u64(lt->total, lt->nr) : 0);
}

static void seq_stats(struct seq_file *m, struct lock_stat_data *data)