diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2025-02-06 02:15:09 -0800 |
|---|---|---|
| committer | Boqun Feng <boqun.feng@gmail.com> | 2025-03-04 18:44:29 -0800 |
| commit | 59bed79ffdbc26af3dfba3c6453a4356c9fd6b6f (patch) | |
| tree | 8c38344a9f118902b53ff476096eecddad79a611 /kernel/context_tracking.c | |
| parent | 69381f38284f107e5e55bff7e51ecd1ef7e3ced8 (diff) | |
context_tracking: Make RCU watch ct_kernel_exit_state() warning
The WARN_ON_ONCE() in ct_kernel_exit_state() follows the call to
ct_state_inc(), which means that RCU is not watching this WARN_ON_ONCE().
This can (and does) result in extraneous lockdep warnings when this
WARN_ON_ONCE() triggers. These extraneous warnings are the opposite
of helpful.
Therefore, invert the WARN_ON_ONCE() condition and move it before the
call to ct_state_inc(). This does mean that the ct_state_inc() return
value can no longer be used in the WARN_ON_ONCE() condition, so discard
this return value and instead use a call to rcu_is_watching_curr_cpu().
This call is executed only in CONFIG_RCU_EQS_DEBUG=y kernels, so there
is no added overhead in production use.
[Boqun: Add the subsystem tag in the title]
Reported-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/bd911cd9-1fe9-447c-85e0-ea811a1dc896@paulmck-laptop
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Diffstat (limited to 'kernel/context_tracking.c')
| -rw-r--r-- | kernel/context_tracking.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 938c48952d26..fb5be6e9b423 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -80,17 +80,16 @@ static __always_inline void rcu_task_trace_heavyweight_exit(void) */ static noinstr void ct_kernel_exit_state(int offset) { - int seq; - /* * CPUs seeing atomic_add_return() must see prior RCU read-side * critical sections, and we also must force ordering with the * next idle sojourn. */ rcu_task_trace_heavyweight_enter(); // Before CT state update! - seq = ct_state_inc(offset); - // RCU is no longer watching. Better be in extended quiescent state! - WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & CT_RCU_WATCHING)); + // RCU is still watching. Better not be in extended quiescent state! + WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !rcu_is_watching_curr_cpu()); + (void)ct_state_inc(offset); + // RCU is no longer watching. } /* |