From ad7c946b35ad455417fdd4bc0e17deda4011841b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 8 Jan 2018 14:35:52 -0800 Subject: rcu: Create RCU-specific workqueues with rescuers RCU's expedited grace periods can participate in out-of-memory deadlocks due to all available system_wq kthreads being blocked and there not being memory available to create more. This commit prevents such deadlocks by allocating an RCU-specific workqueue_struct at early boot time, and providing it with a rescuer to ensure forward progress. This uses the shiny new init_rescuer() function provided by Tejun (but indirectly). This commit also causes SRCU to use this new RCU-specific workqueue_struct. Note that SRCU's use of workqueues never blocks them waiting for readers, so this should be safe from a forward-progress viewpoint. Note that this moves SRCU from system_power_efficient_wq to a normal workqueue. In the unlikely event that this results in measurable degradation, a separate power-efficient workqueue will be creates for SRCU. Reported-by: Prateek Sood Reported-by: Tejun Heo Signed-off-by: Paul E. McKenney Acked-by: Tejun Heo --- kernel/rcu/rcu.h | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/rcu/rcu.h') diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 1c868bcfd705..7a693e31184a 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -485,6 +485,7 @@ void show_rcu_gp_kthreads(void); void rcu_force_quiescent_state(void); void rcu_bh_force_quiescent_state(void); void rcu_sched_force_quiescent_state(void); +extern struct workqueue_struct *rcu_gp_wq; #endif /* #else #ifdef CONFIG_TINY_RCU */ #ifdef CONFIG_RCU_NOCB_CPU -- cgit