This is a note to let you know that I've just added the patch titled
entry: Explicitly flush pending rcuog wakeup before last rescheduling point
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
entry-explicitly-flush-pending-rcuog-wakeup-before-last-rescheduling-point.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 47b8ff194c1fd73d58dc339b597d466fe48c8958 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@xxxxxxxxxx>
Date: Mon, 1 Feb 2021 00:05:47 +0100
Subject: entry: Explicitly flush pending rcuog wakeup before last rescheduling point
From: Frederic Weisbecker <frederic@xxxxxxxxxx>
commit 47b8ff194c1fd73d58dc339b597d466fe48c8958 upstream.
Following the idle loop model, cleanly check for pending rcuog wakeup
before the last rescheduling point on resuming to user mode. This
way we can avoid to do it from rcu_user_enter() with the last resort
self-IPI hack that enforces rescheduling.
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20210131230548.32970-5-frederic@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/entry/common.c | 7 +++++++
kernel/rcu/tree.c | 12 +++++++-----
2 files changed, 14 insertions(+), 5 deletions(-)
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -174,6 +174,10 @@ static unsigned long exit_to_user_mode_l
* enabled above.
*/
local_irq_disable_exit_to_user();
+
+ /* Check if any of the above work has queued a deferred wakeup */
+ rcu_nocb_flush_deferred_wakeup();
+
ti_work = READ_ONCE(current_thread_info()->flags);
}
@@ -187,6 +191,9 @@ static void exit_to_user_mode_prepare(st
lockdep_assert_irqs_disabled();
+ /* Flush pending rcuog wakeup before the last need_resched() check */
+ rcu_nocb_flush_deferred_wakeup();
+
if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
ti_work = exit_to_user_mode_loop(regs, ti_work);
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -699,13 +699,15 @@ noinstr void rcu_user_enter(void)
lockdep_assert_irqs_disabled();
/*
- * We may be past the last rescheduling opportunity in the entry code.
- * Trigger a self IPI that will fire and reschedule once we resume to
- * user/guest mode.
+ * Other than generic entry implementation, we may be past the last
+ * rescheduling opportunity in the entry code. Trigger a self IPI
+ * that will fire and reschedule once we resume in user/guest mode.
*/
instrumentation_begin();
- if (do_nocb_deferred_wakeup(rdp) && need_resched())
- irq_work_queue(this_cpu_ptr(&late_wakeup_work));
+ if (!IS_ENABLED(CONFIG_GENERIC_ENTRY) || (current->flags & PF_VCPU)) {
+ if (do_nocb_deferred_wakeup(rdp) && need_resched())
+ irq_work_queue(this_cpu_ptr(&late_wakeup_work));
+ }
instrumentation_end();
rcu_eqs_enter(true);
Patches currently in stable-queue which might be from frederic@xxxxxxxxxx are
queue-5.10/entry-explicitly-flush-pending-rcuog-wakeup-before-last-rescheduling-point.patch
queue-5.10/rcu-nocb-perform-deferred-wake-up-before-last-idle-s-need_resched-check.patch
queue-5.10/kprobes-fix-to-delay-the-kprobes-jump-optimization.patch
queue-5.10/rcu-nocb-trigger-self-ipi-on-late-deferred-wake-up-before-user-resume.patch
queue-5.10/rcu-pull-deferred-rcuog-wake-up-to-rcu_eqs_enter-callers.patch
queue-5.10/entry-kvm-explicitly-flush-pending-rcuog-wakeup-before-last-rescheduling-point.patch
