From 3e9cc688e56cc2abb9b6067f57c8397f6c96d42c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 23 Sep 2021 18:54:44 +0200 Subject: sched: Make cond_resched_lock() variants RT aware The __might_resched() checks in the cond_resched_lock() variants use PREEMPT_LOCK_OFFSET for preempt count offset checking which takes the preemption disable by the spin_lock() which is still held at that point into account. On PREEMPT_RT enabled kernels spin/rw_lock held sections stay preemptible which means PREEMPT_LOCK_OFFSET is 0, but that still triggers the __might_resched() check because that takes RCU read side nesting into account. On RT enabled kernels spin/read/write_lock() issue rcu_read_lock() to resemble the !RT semantics, which means in cond_resched_lock() the might resched check will see preempt_count() == 0 and rcu_preempt_depth() == 1. Introduce PREEMPT_LOCK_SCHED_OFFSET for those might resched checks and map them depending on CONFIG_PREEMPT_RT. Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210923165358.305969211@linutronix.de --- include/linux/preempt.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include/linux/preempt.h') diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 4d244e295e85..031898b38d06 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -122,9 +122,10 @@ * The preempt_count offset after spin_lock() */ #if !defined(CONFIG_PREEMPT_RT) -#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET +#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET #else -#define PREEMPT_LOCK_OFFSET 0 +/* Locks on RT do not disable preemption */ +#define PREEMPT_LOCK_OFFSET 0 #endif /* -- cgit