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rcu: Protect ->gp_flags accesses with ACCESS_ONCE()

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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.roytman@oracle.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2014-02-18 09:47:13 -08:00
parent c9eaa447e7
commit 91dc95427a
1 changed files with 6 additions and 6 deletions
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12
kernel/rcu/tree.c
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@ -1403,12 +1403,12 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_bind_gp_kthread(); rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock); raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_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. */ /* Spurious wakeup, tell caller to go back to sleep. */
raw_spin_unlock_irq(&rnp->lock); raw_spin_unlock_irq(&rnp->lock);
return 0; 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))) { 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) { if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
raw_spin_lock_irq(&rnp->lock); raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_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); raw_spin_unlock_irq(&rnp->lock);
} }
return fqs_state; return fqs_state;
@ -1566,7 +1566,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
rdp = this_cpu_ptr(rsp->rda); rdp = this_cpu_ptr(rsp->rda);
rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */
if (cpu_needs_another_gp(rsp, rdp)) { 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, trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum), ACCESS_ONCE(rsp->gpnum),
TPS("newreq")); TPS("newreq"));
@ -1695,7 +1695,7 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
*/ */
return; 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), trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
TPS("newreq")); TPS("newreq"));
@ -2320,7 +2320,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp_old->lock, flags); raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
return; /* Someone beat us to it. */ 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); raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */ wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
} }