Messages in this thread Patch in this message | | | Date | Fri, 23 Mar 2018 22:12:24 +0100 (CET) | From | Thomas Gleixner <> | Subject | rcu: Add might_sleep() check to synchronize_rcu() |
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Subject: rcu: Add might_sleep() check to synchronize_rcu() From: Thomas Gleixner <tglx@linutronix.de> 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 <joelaf@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> --- 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
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