Subject: rcu: Add might_sleep() check to synchronize_rcu() From: Thomas Gleixner <[email protected]> Date: Fri, 23 Mar 2018 22:02:18 +0100
Joel reported a debugobjects warning which is triggered by a RCU callback invoking synchronize_rcu(). RCU callbacks run in softirq context, so calling synchronize_rcu() is a bad idea as it might sleep. debugobjects triggers because __wait_rcu_gp() uses on stack objects and invokes debug_object_init_on_stack(). That function checks the object address against current's task stack, which fails because the code runs on the softirq stack. synchronize_rcu() lacks a might_sleep() check which would have caught that issue way earlier because it would trigger with the minimal debug options enabled. Add a might_sleep() check to catch such cases. Reported-by: Joel Fernandes <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Josh Triplett <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Lai Jiangshan <[email protected]> --- kernel/rcu/tree_plugin.h | 1 + 1 file changed, 1 insertion(+) --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -753,6 +753,7 @@ void synchronize_rcu(void) "Illegal synchronize_rcu() in RCU read-side critical section"); if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return; + might_sleep(); if (rcu_gp_is_expedited()) synchronize_rcu_expedited(); else
