[PATCH tip/core/rcu 09/19] rcu: Protect uses of ->jiffies_stall with ACCESS_ONCE()

[Paul E. McKenney]

From: Himangi Saraogi <himangi...@gmail.com>

Some of the accesses to the rcu_state structure's ->jiffies_stall
field are unprotected. This patch protects them with ACCESS_ONCE().
The following coccinelle script was used to acheive this:
/* coccinelle script to protect uses of ->jiffies_stall with ACCESS_ONCE() */
@@
identifier a;
@@
(
        ACCESS_ONCE(a->jiffies_stall)
|
-       a->jiffies_stall
+       ACCESS_ONCE(a->jiffies_stall)
)

Signed-off-by: Himangi Saraogi <himangi...@gmail.com>
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
---
 kernel/rcu/tiny_plugin.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h
index 431528520562..858c56569127 100644
--- a/kernel/rcu/tiny_plugin.h
+++ b/kernel/rcu/tiny_plugin.h
@@ -144,7 +144,7 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
                return;
        rcp->ticks_this_gp++;
        j = jiffies;
-       js = rcp->jiffies_stall;
+       js = ACCESS_ONCE(rcp->jiffies_stall);
        if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
                pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx 
(t=%lu jiffies q=%ld)\n",
                       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
@@ -152,17 +152,17 @@ static void check_cpu_stall(struct rcu_ctrlblk *rcp)
                dump_stack();
        }
        if (*rcp->curtail && ULONG_CMP_GE(j, js))
-               rcp->jiffies_stall = jiffies +
+               ACCESS_ONCE(rcp->jiffies_stall) = jiffies +
                        3 * rcu_jiffies_till_stall_check() + 3;
        else if (ULONG_CMP_GE(j, js))
-               rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+               ACCESS_ONCE(rcp->jiffies_stall) = jiffies + 
rcu_jiffies_till_stall_check();
 }
 
 static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
 {
        rcp->ticks_this_gp = 0;
        rcp->gp_start = jiffies;
-       rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+       ACCESS_ONCE(rcp->jiffies_stall) = jiffies + 
rcu_jiffies_till_stall_check();
 }
 
 static void check_cpu_stalls(void)
-- 
1.8.1.5

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