The following commit has been merged into the core/rcu branch of tip:
Commit-ID: 69cdea873cde261586a2cae2440178df1a313bbe
Gitweb: https://git.kernel.org/tip/69cdea873cde261586a2cae2440178df1a313bbe
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate: Fri, 13 Nov 2020 13:13:23 +01:00
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Wed, 06 Jan 2021 16:24:59 -08:00
rcu/nocb: Shutdown nocb timer on de-offloading
This commit ensures that the nocb timer is shut down before reaching the
final de-offloaded state. The key goal is to prevent the timer handler
from manipulating the callbacks without the protection of the nocb locks.
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Inspired-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Tested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.h | 1 +
kernel/rcu/tree_plugin.h | 12 +++++++++++-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index e0deb48..5d359b9 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -257,6 +257,7 @@ struct rcu_data {
};
/* Values for nocb_defer_wakeup field in struct rcu_data. */
+#define RCU_NOCB_WAKE_OFF -1
#define RCU_NOCB_WAKE_NOT 0
#define RCU_NOCB_WAKE 1
#define RCU_NOCB_WAKE_FORCE 2
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 03ae1ce..c88ad62 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -1665,6 +1665,8 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force,
static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
const char *reason)
{
+ if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_OFF)
+ return;
if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)
mod_timer(&rdp->nocb_timer, jiffies + 1);
if (rdp->nocb_defer_wakeup < waketype)
@@ -2243,7 +2245,7 @@ static int rcu_nocb_cb_kthread(void *arg)
/* Is a deferred wakeup of rcu_nocb_kthread() required? */
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
{
- return READ_ONCE(rdp->nocb_defer_wakeup);
+ return READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT;
}
/* Do a deferred wakeup of rcu_nocb_kthread(). */
@@ -2337,6 +2339,12 @@ static int __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
swait_event_exclusive(rdp->nocb_state_wq,
!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB |
SEGCBLIST_KTHREAD_GP));
+ /* Make sure nocb timer won't stay around */
+ rcu_nocb_lock_irqsave(rdp, flags);
+ WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ del_timer_sync(&rdp->nocb_timer);
+
return ret;
}
@@ -2394,6 +2402,8 @@ static int __rcu_nocb_rdp_offload(struct rcu_data *rdp)
* SEGCBLIST_SOFTIRQ_ONLY mode.
*/
raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
+ /* Re-enable nocb timer */
+ WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
/*
* We didn't take the nocb lock while working on the
* rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode.
|