diff options
| author | Frederic Weisbecker <frederic@kernel.org> | 2020-11-13 13:13:23 +0100 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-01-07 01:24:59 +0100 |
| commit | 69cdea873cde261586a2cae2440178df1a313bbe (patch) | |
| tree | 2d8d8b7c06c6654eee14de2aa0e72de3aaee6aaa /kernel | |
| parent | rcu/nocb: Re-offload support (diff) | |
| download | linux-69cdea873cde261586a2cae2440178df1a313bbe.tar.xz linux-69cdea873cde261586a2cae2440178df1a313bbe.zip | |
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@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rcu/tree.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 12 |
2 files changed, 12 insertions, 1 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index e0deb4829847..5d359b9f9fec 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 03ae1ce4790f..c88ad628595b 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. |