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Commit 4ee0a603 authored by Dongdong Deng's avatar Dongdong Deng Committed by Paul E. McKenney
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rcu: using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value 



Using ACCESS_ONCE() to observe the jiffies_stall/rnp->qsmask value
due to the caller didn't hold the root_rcu/rnp node's lock.  Although
use without ACCESS_ONCE() is safe due to the value loaded being used
but once, the ACCESS_ONCE() is a good documentation aid -- the variables
are being loaded without the services of a lock.

Signed-off-by: default avatarDongdong Deng <dongdong.deng@windriver.com>
CC: Dipankar Sarma <dipankar@in.ibm.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent b0a0f667

kernel/rcutree.c

+2 −2
Original line number Diff line number Diff line
@@ -545,9 +545,9 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) 


	if (rcu_cpu_stall_suppress)

		return;

	delta = jiffies - rsp->jiffies_stall;

	delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);

	rnp = rdp->mynode;

	if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {

	if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) {



		/* We haven't checked in, so go dump stack. */

		print_cpu_stall(rsp);