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Commit 4fc5b755 authored by Iulia Manda's avatar Iulia Manda Committed by Paul E. McKenney
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rcu: Protect uses of jiffies_stall field with ACCESS_ONCE() 



Some of the uses of the rcu_state structure's ->jiffies_stall field
do not use ACCESS_ONCE(), despite there being unprotected accesses.
This commit therefore uses the ACCESS_ONCE() macro to protect this field.

Signed-off-by: default avatarIulia Manda <iulia.manda21@gmail.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 9b67122a

kernel/rcu/tree.c

+6 −6
Original line number Diff line number Diff line
@@ -865,7 +865,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp) 
	rsp->gp_start = j;

	smp_wmb(); /* Record start time before stall time. */

	j1 = rcu_jiffies_till_stall_check();

	rsp->jiffies_stall = j + j1;

	ACCESS_ONCE(rsp->jiffies_stall) = j + j1;

	rsp->jiffies_resched = j + j1 / 2;

}
@@ -904,12 +904,12 @@ static void print_other_cpu_stall(struct rcu_state *rsp) 
	/* Only let one CPU complain about others per time interval. */



	raw_spin_lock_irqsave(&rnp->lock, flags);

	delta = jiffies - rsp->jiffies_stall;

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

	if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {

		raw_spin_unlock_irqrestore(&rnp->lock, flags);

		return;

	}

	rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;

	ACCESS_ONCE(rsp->jiffies_stall) = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;

	raw_spin_unlock_irqrestore(&rnp->lock, flags);



	/*
@@ -992,8 +992,8 @@ static void print_cpu_stall(struct rcu_state *rsp) 
		dump_stack();



	raw_spin_lock_irqsave(&rnp->lock, flags);

	if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))

		rsp->jiffies_stall = jiffies +

	if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall)))

		ACCESS_ONCE(rsp->jiffies_stall) = jiffies +

				     3 * rcu_jiffies_till_stall_check() + 3;

	raw_spin_unlock_irqrestore(&rnp->lock, flags);
@@ -1077,7 +1077,7 @@ void rcu_cpu_stall_reset(void) 
	struct rcu_state *rsp;



	for_each_rcu_flavor(rsp)

		rsp->jiffies_stall = jiffies + ULONG_MAX / 2;

		ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2;

}



/*