rcu: get rid of signed overflow in check_cpu_stall()

Signed integer overflow is undefined by the C standard, so move
calculations to unsigned.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 78923a50cdb238a1b2d8a29f16e7ad6b58cdce96..b2fe2a273df2eb442f1d3a56a766cf92cc94fcf8 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -581,21 +581,24 @@ static void print_cpu_stall(struct rcu_state *rsp)
 
 static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
 {
-       long delta;
+       unsigned long j;
+       unsigned long js;
        struct rcu_node *rnp;
 
        if (rcu_cpu_stall_suppress)
                return;
-       delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
+       j = ACCESS_ONCE(jiffies);
+       js = ACCESS_ONCE(rsp->jiffies_stall);
        rnp = rdp->mynode;
-       if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) {
+       if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
 
                /* We haven't checked in, so go dump stack. */
                print_cpu_stall(rsp);
 
-       } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
+       } else if (rcu_gp_in_progress(rsp) &&
+                  ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
 
-               /* They had two time units to dump stack, so complain. */
+               /* They had a few time units to dump stack, so complain. */
                print_other_cpu_stall(rsp);
        }
 }