Skip to content
Browse files

rcu: Move TINY_RCU quiescent state out of extended quiescent state

TINY_RCU's rcu_idle_enter_common() invokes rcu_sched_qs() in order
to inform the RCU core of the quiescent state implied by idle entry.
Of course, idle is also an extended quiescent state, so that the call
to rcu_sched_qs() speeds up RCU's invoking of any callbacks that might
be queued.  This speed-up is important when entering into dyntick-idle
mode -- if there are no further scheduling-clock interrupts, the callbacks
might never be invoked, which could result in a system hang.

However, processing callbacks does event tracing, which in turn
implies RCU read-side critical sections, which are illegal in extended
quiescent states.  This patch therefore moves the call to rcu_sched_qs()
so that it precedes the point at which we inform lockdep that RCU has
entered an extended quiescent state.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  • Loading branch information...
1 parent 58fac09 commit 22a767269a767b3ee91e4aaea353ac6bec6a912d Li Zhong committed with paulmck
Showing with 1 addition and 1 deletion.
  1. +1 −1 kernel/rcutiny.c
View
2 kernel/rcutiny.c
@@ -75,9 +75,9 @@ static void rcu_idle_enter_common(long long newval)
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
+ rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
barrier();
rcu_dynticks_nesting = newval;
- rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
}
/*

0 comments on commit 22a7672

Please sign in to comment.
Something went wrong with that request. Please try again.