The following commit has been merged into the core/rcu branch of tip:
Commit-ID: 1feb2cc8db481b902272559ad7aae3c091762ad0
Gitweb: https://git.kernel.org/tip/1feb2cc8db481b902272559ad7aae3c091762ad0
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate: Mon, 05 Apr 2021 09:47:59 -07:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 10 May 2021 16:22:54 -07:00
lockdep: Explicitly flag likely false-positive report
The reason that lockdep_rcu_suspicious() prints the value of debug_locks
is because a value of zero indicates a likely false positive. This can
work, but is a bit obtuse. This commit therefore explicitly calls out
the possibility of a false positive.
Reviewed-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/locking/lockdep.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 48d736a..d6c3c98 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -6393,6 +6393,7 @@ asmlinkage __visible void lockdep_sys_exit(void)
void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
{
struct task_struct *curr = current;
+ int dl = READ_ONCE(debug_locks);
/* Note: the following can be executed concurrently, so be careful. */
pr_warn("\n");
@@ -6402,11 +6403,12 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
pr_warn("-----------------------------\n");
pr_warn("%s:%d %s!\n", file, line, s);
pr_warn("\nother info that might help us debug this:\n\n");
- pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
+ pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
!rcu_lockdep_current_cpu_online()
? "RCU used illegally from offline CPU!\n"
: "",
- rcu_scheduler_active, debug_locks);
+ rcu_scheduler_active, dl,
+ dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
/*
* If a CPU is in the RCU-free window in idle (ie: in the section
|