From: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
A number of ->gp_flags accesses don't have ACCESS_ONCE(), but all of
the can race against other loads or stores. This commit therefore
applies ACCESS_ONCE() to the unprotected ->gp_flags accesses.
Reported-by: Alexey Roytman <alexey.royt...@oracle.com>
Signed-off-by: Paul E. McKenney <paul...@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 0c47e300210a..2c53ac924cab 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1403,12 +1403,12 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
- if (rsp->gp_flags == 0) {
+ if (!ACCESS_ONCE(rsp->gp_flags)) {
/* Spurious wakeup, tell caller to go back to sleep. */
raw_spin_unlock_irq(&rnp->lock);
return 0;
}
- rsp->gp_flags = 0; /* Clear all flags: New grace period. */
+ ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */
if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
/*
@@ -1501,7 +1501,7 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int
fqs_state_in)
if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
- rsp->gp_flags &= ~RCU_GP_FLAG_FQS;
+ ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS;
raw_spin_unlock_irq(&rnp->lock);
}
return fqs_state;
@@ -1566,7 +1566,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
rdp = this_cpu_ptr(rsp->rda);
rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */
if (cpu_needs_another_gp(rsp, rdp)) {
- rsp->gp_flags = RCU_GP_FLAG_INIT;
+ ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("newreq"));
@@ -1695,7 +1695,7 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct
rcu_node *rnp,
*/
return;
}
- rsp->gp_flags = RCU_GP_FLAG_INIT;
+ ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
TPS("newreq"));
@@ -2320,7 +2320,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
return; /* Someone beat us to it. */
}
- rsp->gp_flags |= RCU_GP_FLAG_FQS;
+ ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS;
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
}
--
1.8.1.5
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