On 2024-07-18, Andrew Halaney <ahalaney@xxxxxxxxxx> wrote: > [ 5.061942] ============================= > [ 5.061942] WARNING: suspicious RCU usage > [ 5.061942] 5.14.0-467.el9.x86_64+debug #1 Not tainted > [ 5.061942] ----------------------------- > [ 5.061942] kernel/printk/nbcon.c:1118 suspicious rcu_dereference_check() usage! In Petr Mladek's review of my latest printk-threading series, he pointed out [0] that I was using the wrong RCU API in rcuwait_has_sleeper(). The patch below was his suggestion, which I was already folding into the next version of my series. John Ogness [0] https://lore.kernel.org/lkml/ZmsLcu2tHmCfLiu0@xxxxxxxxxxxxxxx diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 0951c2c7fb1b..da462661876c 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1181,9 +1181,6 @@ static void nbcon_irq_work(struct irq_work *irq_work) static inline bool rcuwait_has_sleeper(struct rcuwait *w) { - bool has_sleeper; - - rcu_read_lock(); /* * Guarantee any new records can be seen by tasks preparing to wait * before this context checks if the rcuwait is empty. @@ -1196,10 +1193,7 @@ static inline bool rcuwait_has_sleeper(struct rcuwait *w) * This pairs with nbcon_kthread_func:A. */ smp_mb(); /* LMM(rcuwait_has_sleeper:A) */ - has_sleeper = !!rcu_dereference(w->task); - rcu_read_unlock(); - - return has_sleeper; + return rcuwait_active(w); } /**
