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Subject[PATCH tip/core/rcu 06/19] rcu: Protect uses of jiffies_stall field with ACCESS_ONCE()
Date
From: Iulia Manda <iulia.manda21@gmail.com>

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: Iulia Manda <iulia.manda21@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2cc39c781085..c624415f8386 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -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;
}

/*
--
1.8.1.5


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