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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-04-28 20:11:09 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-06-08 18:51:59 -0700 |
| commit | 6b5fc3a1331810db407c9e0e673dc1837afdc9d0 (patch) | |
| tree | 00ad3040ed3d6ece09a681ea1e531fdc2a5e4bab /kernel | |
| parent | 511324e462a12ea8be1a7e5fc63a992134db80d7 (diff) | |
| download | linux-6b5fc3a1331810db407c9e0e673dc1837afdc9d0.tar.gz linux-6b5fc3a1331810db407c9e0e673dc1837afdc9d0.tar.bz2 linux-6b5fc3a1331810db407c9e0e673dc1837afdc9d0.zip | |
rcu: Add memory barriers for NOCB leader wakeup
Wait/wakeup operations do not guarantee ordering on their own. Instead,
either locking or memory barriers are required. This commit therefore
adds memory barriers to wake_nocb_leader() and nocb_leader_wait().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: <stable@vger.kernel.org> # 4.6.x
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 0b1042545116..573fbe9640a0 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1810,6 +1810,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force) if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) { /* Prior smp_mb__after_atomic() orders against prior enqueue. */ WRITE_ONCE(rdp_leader->nocb_leader_sleep, false); + smp_mb(); /* ->nocb_leader_sleep before swake_up(). */ swake_up(&rdp_leader->nocb_wq); } } @@ -2064,6 +2065,7 @@ wait_again: * nocb_gp_head, where they await a grace period. */ gotcbs = false; + smp_mb(); /* wakeup before ->nocb_head reads. */ for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head); if (!rdp->nocb_gp_head) |