From 91dc95427a0d30ac2c58d6e943c7f40a3f25d908 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 18 Feb 2014 09:47:13 -0800 Subject: rcu: Protect ->gp_flags accesses with ACCESS_ONCE() 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 Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcu/tree.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel/rcu') 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. */ } -- cgit v1.2.3