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[PATCH RT 00/20] Linux 3.18.27-rt27-rc1

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  [PATCH RT 00/20] Linux 3.18.27-rt27-rc1 Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
    [PATCH RT 12/20] tick/broadcast: Make broadcast hrtimer irqsafe Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
    [PATCH RT 01/20] sched: reset tasks lockless wake-queues on fork() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
    [PATCH RT 04/20] preempt-lazy: Add the lazy-preemption check to preempt_schedule() Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100
    [PATCH RT 09/20] kernel: migrate_disable() do fastpath in atomic & irqs-off Steven Rostedt <rostedt@goodmis.org> - 2016-03-02 16:50 +0100

#1348205 — [PATCH RT 00/20] Linux 3.18.27-rt27-rc1

Dear RT Folks,

This is the RT stable review cycle of patch 3.18.27-rt27-rc1.

Please scream at me if I messed something up. Please test the patches too.

The -rc release will be uploaded to kernel.org and will be deleted when
the final release is out. This is just a review release (or release candidate).

The pre-releases will not be pushed to the git repository, only the
final release is.

If all goes well, this patch will be converted to the next main release
on 3/7/2016.

Enjoy,

-- Steve


To build 3.18.27-rt27-rc1 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.18.tar.xz

  http://www.kernel.org/pub/linux/kernel/v3.x/patch-3.18.27.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/3.18/patch-3.18.27-rt27-rc1.patch.xz

You can also build from 3.18.27-rt26 by applying the incremental patch:

http://www.kernel.org/pub/linux/kernel/projects/rt/3.18/incr/patch-3.18.27-rt26-rt27-rc1.patch.xz


Changes from 3.18.27-rt26:

---


Clark Williams (1):
      rcu/torture: Comment out rcu_bh ops on PREEMPT_RT_FULL

Mike Galbraith (3):
      sched,rt: __always_inline preemptible_lazy()
      drm,radeon,i915: Use preempt_disable/enable_rt() where recommended
      drm,i915: Use local_lock/unlock_irq() in intel_pipe_update_start/end()

Sebastian Andrzej Siewior (11):
      sched: reset task's lockless wake-queues on fork()
      ptrace: don't open IRQs in ptrace_freeze_traced() too early
      net: move xmit_recursion to per-task variable on -RT
      preempt-lazy: Add the lazy-preemption check to preempt_schedule()
      softirq: split timer softirqs out of ksoftirqd
      net: provide a way to delegate processing a softirq to ksoftirqd
      latencyhist: disable jump-labels
      kernel: migrate_disable() do fastpath in atomic & irqs-off
      kernel: softirq: unlock with irqs on
      kernel/stop_machine: partly revert "stop_machine: Use raw spinlocks"
      kernel: sched: Fix preempt_disable_ip recodring for preempt_disable()

Steven Rostedt (Red Hat) (1):
      Linux 3.18.27-rt27-rc1

Thomas Gleixner (1):
      tick/broadcast: Make broadcast hrtimer irqsafe

Yang Shi (3):
      arm64: replace read_lock to rcu lock in call_step_hook
      trace: Use rcuidle version for preemptoff_hist trace point
      f2fs: Mutex can't be used by down_write_nest_lock()

----
 arch/Kconfig                            |   1 +
 arch/arm64/kernel/debug-monitors.c      |  21 +++---
 drivers/gpu/drm/i915/i915_irq.c         |   2 +
 drivers/gpu/drm/i915/intel_sprite.c     |  11 ++--
 drivers/gpu/drm/radeon/radeon_display.c |   2 +
 fs/f2fs/f2fs.h                          |   4 +-
 include/linux/ftrace.h                  |  12 ++++
 include/linux/interrupt.h               |   8 +++
 include/linux/netdevice.h               |   9 +++
 include/linux/sched.h                   |   3 +-
 include/trace/events/hist.h             |   1 +
 kernel/fork.c                           |   1 +
 kernel/ptrace.c                         |   6 +-
 kernel/rcu/rcutorture.c                 |   7 ++
 kernel/sched/core.c                     |  52 ++++++++-------
 kernel/softirq.c                        | 112 ++++++++++++++++++++++++++++----
 kernel/stop_machine.c                   |  40 +++---------
 kernel/time/tick-broadcast-hrtimer.c    |   1 +
 kernel/trace/trace_irqsoff.c            |   8 +--
 localversion-rt                         |   2 +-
 net/core/dev.c                          |  43 ++++++++++--
 21 files changed, 249 insertions(+), 97 deletions(-)

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#1348206 — [PATCH RT 12/20] tick/broadcast: Make broadcast hrtimer irqsafe

3.18.27-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

Otherwise we end up with the following:

|=================================
|[ INFO: inconsistent lock state ]
|4.4.2-rt7+ #5 Not tainted
|---------------------------------
|inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
|ktimersoftd/0/4 [HC0[0]:SC0[0]:HE1:SE1] takes:
| (tick_broadcast_lock){?.....}, at: [<ffffffc000150db4>] tick_handle_oneshot_broadcast+0x58/0x27c
|{IN-HARDIRQ-W} state was registered at:
|  [<ffffffc000118198>] mark_lock+0x19c/0x6a0
|  [<ffffffc000119728>] __lock_acquire+0xb1c/0x2100
|  [<ffffffc00011b560>] lock_acquire+0xf8/0x230
|  [<ffffffc00061bf08>] _raw_spin_lock_irqsave+0x50/0x68
|  [<ffffffc000152188>] tick_broadcast_switch_to_oneshot+0x20/0x60
|  [<ffffffc0001529f4>] tick_switch_to_oneshot+0x64/0xd8
|  [<ffffffc000152b00>] tick_init_highres+0x1c/0x24
|  [<ffffffc000141e58>] hrtimer_run_queues+0x78/0x100
|  [<ffffffc00013f804>] update_process_times+0x38/0x74
|  [<ffffffc00014fc5c>] tick_periodic+0x60/0x140
|  [<ffffffc00014fd68>] tick_handle_periodic+0x2c/0x94
|  [<ffffffc00052b878>] arch_timer_handler_phys+0x3c/0x48
|  [<ffffffc00012d078>] handle_percpu_devid_irq+0x100/0x390
|  [<ffffffc000127f34>] generic_handle_irq+0x34/0x4c
|  [<ffffffc000128300>] __handle_domain_irq+0x90/0xf8
|  [<ffffffc000082554>] gic_handle_irq+0x5c/0xa4
|  [<ffffffc0000855ac>] el1_irq+0x6c/0xec
|  [<ffffffc000112bec>] default_idle_call+0x2c/0x44
|  [<ffffffc000113058>] cpu_startup_entry+0x3cc/0x410
|  [<ffffffc0006169f8>] rest_init+0x158/0x168
|  [<ffffffc000888954>] start_kernel+0x3a0/0x3b4
|  [<0000000080621000>] 0x80621000
|irq event stamp: 18723
|hardirqs last  enabled at (18723): [<ffffffc00061c188>] _raw_spin_unlock_irq+0x38/0x80
|hardirqs last disabled at (18722): [<ffffffc000140a4c>] run_hrtimer_softirq+0x2c/0x2f4
|softirqs last  enabled at (0): [<ffffffc0000c4744>] copy_process.isra.50+0x300/0x16d4
|softirqs last disabled at (0): [<          (null)>]           (null)

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/time/tick-broadcast-hrtimer.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c
index 6aac4beedbbe..943c03395e46 100644
--- a/kernel/time/tick-broadcast-hrtimer.c
+++ b/kernel/time/tick-broadcast-hrtimer.c
@@ -109,5 +109,6 @@ void tick_setup_hrtimer_broadcast(void)
 {
 	hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 	bctimer.function = bc_handler;
+	bctimer.irqsafe = true;
 	clockevents_register_device(&ce_broadcast_hrtimer);
 }
-- 
2.7.0

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#1348208 — [PATCH RT 01/20] sched: reset tasks lockless wake-queues on fork()

3.18.27-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

In 7675104990ed ("sched: Implement lockless wake-queues") we gained
lockless wake-queues. -RT managed to lockup itself with those. There
could be multiple attempts for task X to enqueue it for a wakeup
_even_ if task X is already running.
The reason is that task X could be runnable but not yet on CPU. The the
task performing the wakeup did not leave the CPU it could performe
multiple wakeups.
With the proper timming task X could be running and enqueued for a
wakeup. If this happens while X is performing a fork() then its its
child will have a !NULL `wake_q` member copied.
This is not a problem as long as the child task does not participate in
lockless wakeups :)

Fixes: 7675104990ed ("sched: Implement lockless wake-queues")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/fork.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/fork.c b/kernel/fork.c
index 3a8ecfb38831..1c4edaf4ec36 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -364,6 +364,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
 #endif
 	tsk->splice_pipe = NULL;
 	tsk->task_frag.page = NULL;
+	tsk->wake_q.next = NULL;
 
 	account_kernel_stack(ti, 1);
 
-- 
2.7.0

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#1348215 — [PATCH RT 04/20] preempt-lazy: Add the lazy-preemption check to preempt_schedule()

3.18.27-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Probably in the rebase onto v4.1 this check got moved into less commonly used
preempt_schedule_notrace(). This patch ensures that both functions use it.

Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/sched/core.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9e01a8f358f8..8214206817f2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3164,6 +3164,30 @@ void __sched schedule_preempt_disabled(void)
 	preempt_disable();
 }
 
+#ifdef CONFIG_PREEMPT_LAZY
+/*
+ * If TIF_NEED_RESCHED is then we allow to be scheduled away since this is
+ * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
+ * preempt_lazy_count counter >0.
+ */
+static int preemptible_lazy(void)
+{
+	if (test_thread_flag(TIF_NEED_RESCHED))
+		return 1;
+	if (current_thread_info()->preempt_lazy_count)
+		return 0;
+	return 1;
+}
+
+#else
+
+static int preemptible_lazy(void)
+{
+	return 1;
+}
+
+#endif
+
 #ifdef CONFIG_PREEMPT
 /*
  * this is the entry point to schedule() from in-kernel preemption
@@ -3178,15 +3202,9 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
 	 */
 	if (likely(!preemptible()))
 		return;
-
-#ifdef CONFIG_PREEMPT_LAZY
-	/*
-	 * Check for lazy preemption
-	 */
-	if (current_thread_info()->preempt_lazy_count &&
-			!test_thread_flag(TIF_NEED_RESCHED))
+	if (!preemptible_lazy())
 		return;
-#endif
+
 	do {
 		__preempt_count_add(PREEMPT_ACTIVE);
 		/*
-- 
2.7.0

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#1348216 — [PATCH RT 09/20] kernel: migrate_disable() do fastpath in atomic & irqs-off

3.18.27-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

With interrupts off it makes no sense to do the long path since we can't
leave the CPU anyway. Also we might end up in a recursion with lockdep.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/sched/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 8214206817f2..24c7ced53555 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2859,7 +2859,7 @@ void migrate_disable(void)
 {
 	struct task_struct *p = current;
 
-	if (in_atomic()) {
+	if (in_atomic() || irqs_disabled()) {
 #ifdef CONFIG_SCHED_DEBUG
 		p->migrate_disable_atomic++;
 #endif
@@ -2893,7 +2893,7 @@ void migrate_enable(void)
 	unsigned long flags;
 	struct rq *rq;
 
-	if (in_atomic()) {
+	if (in_atomic() || irqs_disabled()) {
 #ifdef CONFIG_SCHED_DEBUG
 		p->migrate_disable_atomic--;
 #endif
-- 
2.7.0

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