Commit 4ee0a603 authored Sep 28, 2010 by Dongdong Deng Committed by Paul E. McKenney Oct 07, 2010

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: Dongdong Deng <dongdong.deng@windriver.com>
CC: Dipankar Sarma <dipankar@in.ibm.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paul 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);

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