[ANNOUNCE] v4.16.18-rt12
Dear RT folks!
I'm pleased to announce the v4.16.18-rt12 patch set.
Changes since v4.16.18-rt11:
- Mark RCU's "rcu_iw" irqwork to be invoked in hardirq context as
expected by RCU. Reported by John Ogness.
- Drop the "is_special_task_state()" check from rtmutex's custom
set_state function. This avoids a warning if the sleeping-lock code
is restoring back to this "special" state.
- If a kworker invokes schedule() it is possible that it wakes another
kworker and invokes schedule() again. Try to avoid the second
schedule(). Reported and patched by Daniel Bristot de Oliveira.
- Enable XEN on ARM64. Iain Hunter reported that there are no problems
with it so there is no reason to keep disabled.
Known issues
- A warning triggered in "rcu_note_context_switch" originated from
SyS_timer_gettime(). The issue was always there, it is now
visible. Reported by Grygorii Strashko and Daniel Wagner.
The delta patch against v4.16.18-rt11 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.16/incr/patch-4.16.18-rt11-rt12.patch.xz
You can get this release via the git tree at:
git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.16.18-rt12
The RT patch against v4.16.18 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patch-4.16.18-rt12.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.18-rt12.tar.xz
Sebastian
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
diff --git a/patches/Revert-arm64-xen-Make-XEN-depend-on-RT.patch b/patches/Revert-arm64-xen-Make-XEN-depend-on-RT.patch
new file mode 100644
index 0000000..e7bef17
--- /dev/null
+++ b/patches/Revert-arm64-xen-Make-XEN-depend-on-RT.patch
@@ -0,0 +1,29 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Thu, 2 Aug 2018 17:11:01 +0200
+Subject: [PATCH] Revert "arm64/xen: Make XEN depend on !RT"
+
+Iain Hunter reported that there are no problems with it so there is no
+reason to keep it disabled.
+
+Reported-by: Iain Hunter <drhunter95@gmail.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ arch/arm64/Kconfig | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
+index d2370c7829451..3a6f0ae739d39 100644
+--- a/arch/arm64/Kconfig
++++ b/arch/arm64/Kconfig
+@@ -861,7 +861,7 @@ config XEN_DOM0
+
+ config XEN
+ bool "Xen guest support on ARM64"
+- depends on ARM64 && OF && !PREEMPT_RT_FULL
++ depends on ARM64 && OF
+ select SWIOTLB_XEN
+ select PARAVIRT
+ help
+--
+2.18.0
+
diff --git a/patches/localversion.patch b/patches/localversion.patch
index 58842b5..12bd473 100644
--- a/patches/localversion.patch
+++ b/patches/localversion.patch
@@ -10,4 +10,4 @@
--- /dev/null
+++ b/localversion-rt
@@ -0,0 +1 @@
-+-rt11
++-rt12
diff --git a/patches/rcu-mark-rcu_iw_handler-as-IRQ_WORK_HARD_IRQ.patch b/patches/rcu-mark-rcu_iw_handler-as-IRQ_WORK_HARD_IRQ.patch
new file mode 100644
index 0000000..075b37c
--- /dev/null
+++ b/patches/rcu-mark-rcu_iw_handler-as-IRQ_WORK_HARD_IRQ.patch
@@ -0,0 +1,31 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Mon, 30 Jul 2018 18:26:48 +0200
+Subject: [PATCH] rcu: mark rcu_iw_handler() as IRQ_WORK_HARD_IRQ
+
+RCU's rcu_iw irq-work (rcu_iw_handler()) acquires the raw spinlock
+rnp->lock without disabling interrupts. The lock is held normally with
+disabled interrupts for a short time.
+Mark irq-work as IRQ_WORK_HARD_IRQ so it is invoked in IRQ context like
+on !RT.
+
+Reported-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/rcu/tree.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
+index 5a9c5abb17da..4fb983f4b9fd 100644
+--- a/kernel/rcu/tree.c
++++ b/kernel/rcu/tree.c
+@@ -1294,6 +1294,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
+ !rdp->rcu_iw_pending && rdp->rcu_iw_gpnum != rnp->gpnum &&
+ (rnp->ffmask & rdp->grpmask)) {
+ init_irq_work(&rdp->rcu_iw, rcu_iw_handler);
++ rdp->rcu_iw.flags = IRQ_WORK_HARD_IRQ;
+ rdp->rcu_iw_pending = true;
+ rdp->rcu_iw_gpnum = rnp->gpnum;
+ irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
+--
+2.18.0
+
diff --git a/patches/sched-core-Avoid-__schedule-being-called-twice-in-a-.patch b/patches/sched-core-Avoid-__schedule-being-called-twice-in-a-.patch
new file mode 100644
index 0000000..c9b4fb8
--- /dev/null
+++ b/patches/sched-core-Avoid-__schedule-being-called-twice-in-a-.patch
@@ -0,0 +1,52 @@
+From: Daniel Bristot de Oliveira <bristot@redhat.com>
+Date: Mon, 30 Jul 2018 15:00:00 +0200
+Subject: [PATCH] sched/core: Avoid __schedule() being called twice in a row
+
+If a worker invokes schedule() then we may have the call chain:
+ schedule()
+ -> sched_submit_work()
+ -> wq_worker_sleeping()
+ -> wake_up_worker()
+ -> wake_up_process().
+
+The last wakeup may cause a schedule which is unnecessary because we are
+already in schedule() and do it anyway.
+
+Add a preempt_disable() + preempt_enable_no_resched() around
+wq_worker_sleeping() so the context switch could be delayed until
+__schedule().
+
+Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
+Cc: Clark Williams <williams@redhat.com>
+Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
+Cc: Romulo da Silva de Oliveira <romulo.deoliveira@ufsc.br>
+Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Cc: Steven Rostedt <rostedt@goodmis.org>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: Ingo Molnar <mingo@redhat.com>
+Cc: Peter Zijlstra <peterz@infradead.org>
+[bigeasy: rewrite changelog]
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/sched/core.c | 8 +++++++-
+ 1 file changed, 7 insertions(+), 1 deletion(-)
+
+--- a/kernel/sched/core.c
++++ b/kernel/sched/core.c
+@@ -3500,9 +3500,15 @@ static inline void sched_submit_work(str
+ /*
+ * If a worker went to sleep, notify and ask workqueue whether
+ * it wants to wake up a task to maintain concurrency.
++ * As this function is called inside the schedule() context,
++ * we disable preemption to avoid it calling schedule() again
++ * in the possible wakeup of a kworker.
+ */
+- if (tsk->flags & PF_WQ_WORKER)
++ if (tsk->flags & PF_WQ_WORKER) {
++ preempt_disable();
+ wq_worker_sleeping(tsk);
++ preempt_enable_no_resched();
++ }
+
+ /*
+ * If we are going to sleep and we have plugged IO queued,
diff --git a/patches/sched-drop-is_special_task_state-check-from-__set_cu.patch b/patches/sched-drop-is_special_task_state-check-from-__set_cu.patch
new file mode 100644
index 0000000..3e028a3
--- /dev/null
+++ b/patches/sched-drop-is_special_task_state-check-from-__set_cu.patch
@@ -0,0 +1,49 @@
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Wed, 1 Aug 2018 10:33:05 +0200
+Subject: [PATCH] sched: drop is_special_task_state() check from
+ __set_current_state_no_track()
+
+The is_special_task_state() check in __set_current_state_no_track()
+has been wrongly placed. __set_current_state_no_track() is used in RT
+while a sleeping lock is acquired. It is used at the begin of the wait
+loop with TASK_UNINTERRUPTIBLE and while leaving it and restoring the
+original state. The latter part triggers the warning.
+
+Drop the special state check. This is only used within the sleeping lock
+implementation and the assignment happens while the PI lock is held.
+While at it, drop set_current_state_no_track() because it has no users.
+
+Cc: stable-rt@vger.kernel.org
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ include/linux/sched.h | 12 +-----------
+ 1 file changed, 1 insertion(+), 11 deletions(-)
+
+--- a/include/linux/sched.h
++++ b/include/linux/sched.h
+@@ -134,16 +134,7 @@ struct task_group;
+ } while (0)
+
+ #define __set_current_state_no_track(state_value) \
+- do { \
+- WARN_ON_ONCE(is_special_task_state(state_value));\
+- current->state = (state_value); \
+- } while (0)
+-
+-#define set_current_state_no_track(state_value) \
+- do { \
+- WARN_ON_ONCE(is_special_task_state(state_value));\
+- smp_store_mb(current->state, (state_value)); \
+- } while (0)
++ current->state = (state_value);
+
+ #define set_special_state(state_value) \
+ do { \
+@@ -199,7 +190,6 @@ struct task_group;
+ smp_store_mb(current->state, (state_value))
+
+ #define __set_current_state_no_track(state_value) __set_current_state(state_value)
+-#define set_current_state_no_track(state_value) set_current_state(state_value)
+
+ /*
+ * set_special_state() should be used for those states when the blocking task
diff --git a/patches/series b/patches/series
index 1344826..6a23888 100644
--- a/patches/series
+++ b/patches/series
@@ -235,6 +235,7 @@
net_disable_NET_RX_BUSY_POLL.patch
arm-disable-NEON-in-kernel-mode.patch
arm64-xen--Make-XEN-depend-on-non-rt.patch
+Revert-arm64-xen-Make-XEN-depend-on-RT.patch
power-use-generic-rwsem-on-rt.patch
powerpc-kvm-Disable-in-kernel-MPIC-emulation-for-PRE.patch
power-disable-highmem-on-rt.patch
@@ -384,6 +385,7 @@
rtmutex-Provide-rt_mutex_slowlock_locked.patch
rtmutex-export-lockdep-less-version-of-rt_mutex-s-lo.patch
rtmutex-add-sleeping-lock-implementation.patch
+sched-drop-is_special_task_state-check-from-__set_cu.patch
rtmutex-add-mutex-implementation-based-on-rtmutex.patch
rtmutex-add-rwsem-implementation-based-on-rtmutex.patch
rtmutex-add-rwlock-implementation-based-on-rtmutex.patch
@@ -448,6 +450,7 @@
workqueue-use-locallock.patch
work-queue-work-around-irqsafe-timer-optimization.patch
workqueue-distangle-from-rq-lock.patch
+sched-core-Avoid-__schedule-being-called-twice-in-a-.patch
# DEBUGOBJECTS
debugobjects-rt.patch
@@ -474,6 +477,7 @@
# irqwork
irqwork-push_most_work_into_softirq_context.patch
irqwork-Move-irq-safe-work-to-irq-context.patch
+rcu-mark-rcu_iw_handler-as-IRQ_WORK_HARD_IRQ.patch
# CONSOLE. NEEDS more thought !!!
printk-rt-aware.patch
diff --git a/patches/workqueue-prevent-deadlock-stall.patch b/patches/workqueue-prevent-deadlock-stall.patch
index b5c60e7..d376f19 100644
--- a/patches/workqueue-prevent-deadlock-stall.patch
+++ b/patches/workqueue-prevent-deadlock-stall.patch
@@ -37,13 +37,13 @@
Cc: Steven Rostedt <rostedt@goodmis.org>
---
- kernel/sched/core.c | 7 ++++--
+ kernel/sched/core.c | 6 +++--
kernel/workqueue.c | 60 ++++++++++++++++++++++++++++++++++++++++------------
- 2 files changed, 52 insertions(+), 15 deletions(-)
+ 2 files changed, 51 insertions(+), 15 deletions(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
-@@ -3550,9 +3550,8 @@ void __noreturn do_task_dead(void)
+@@ -3540,9 +3540,8 @@ void __noreturn do_task_dead(void)
static inline void sched_submit_work(struct task_struct *tsk)
{
@@ -54,11 +54,10 @@
/*
* If a worker went to sleep, notify and ask workqueue whether
* it wants to wake up a task to maintain concurrency.
-@@ -3560,6 +3559,10 @@ static inline void sched_submit_work(str
- if (tsk->flags & PF_WQ_WORKER)
- wq_worker_sleeping(tsk);
+@@ -3556,6 +3555,9 @@ static inline void sched_submit_work(str
+ preempt_enable_no_resched();
+ }
-+
+ if (tsk_is_pi_blocked(tsk))
+ return;
+
