[ANNOUNCE] v4.4.3-rt9

[ANNOUNCE] v4.4.3-rt9

[Thomas Gleixner]

Dear RT folks!

I'm pleased to announce the v4.4.3-rt9 patch set. v4.4.2-rt7 and v4.4.3-rt8
are non-announced updates to incorporate the linux-4.4.y stable tree.

There is one change caused by the 4.4.3 update:

  The relaxed handling of dump_stack() on RT has been dropped as there is
  actually a potential deadlock lurking around the corner. See: commit
  d7ce36924344 upstream. This does not effect the other facilities which
  gather stack traces.

RT changes since v4.4.3-rt8:

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

  Josh Cartwright (1):
      sc16is7xx: Drop bogus use of IRQF_ONESHOT

  Mike Galbraith (4):
      sched,rt: __always_inline preemptible_lazy()
      locking/lglocks: Use preempt_enable/disable_nort() in lg_double_[un]lock
      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 (1):
      kernel: sched: Fix preempt_disable_ip recording for preempt_disable()

  Thomas Gleixner (4):
      iommu/amd: Use WARN_ON_NORT in __attach_device()
      tick/broadcast: Make broadcast hrtimer irqsafe
      trace/writeback: Block cgroup path tracing on RT
      v4.4.3-rt9

  Yang Shi (2):
      trace: Use rcuidle version for preemptoff_hist trace point
      f2fs: Mutex can't be used by down_write_nest_lock()

Known issues:

  - bcache stays disabled

  - CPU hotplug is not better than before

  - The netlink_release() OOPS, reported by Clark, is still on the
    list, but unsolved due to lack of information

The delta patch against 4.4.3-rt8 is appended below and can be found here:

    https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/incr/patch-4.4.3-rt8-rt9.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 v4.4.3-rt9

The RT patch against 4.4.3 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/patch-4.4.3-rt9.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4.3-rt9.tar.xz

Enjoy!

	tglx

8<---------------

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 0d228f909dcb..708b40a842f3 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -812,6 +812,7 @@ static int i915_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
 	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
 
 	/* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */
+	preempt_disable_rt();
 
 	/* Get optional system timestamp before query. */
 	if (stime)
@@ -863,6 +864,7 @@ static int i915_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
 		*etime = ktime_get();
 
 	/* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */
+	preempt_enable_rt();
 
 	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
 
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 56dc132e8e20..8771d6646e91 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -38,6 +38,7 @@
 #include "intel_drv.h"
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
+#include <linux/locallock.h>
 
 static bool
 format_is_yuv(uint32_t format)
@@ -64,6 +65,8 @@ static int usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
 			    1000 * adjusted_mode->crtc_htotal);
 }
 
+static DEFINE_LOCAL_IRQ_LOCK(pipe_update_lock);
+
 /**
  * intel_pipe_update_start() - start update of a set of display registers
  * @crtc: the crtc of which the registers are going to be updated
@@ -96,7 +99,7 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
 	min = vblank_start - usecs_to_scanlines(adjusted_mode, 100);
 	max = vblank_start - 1;
 
-	local_irq_disable();
+	local_lock_irq(pipe_update_lock);
 
 	if (min <= 0 || max <= 0)
 		return;
@@ -126,11 +129,11 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
 			break;
 		}
 
-		local_irq_enable();
+		local_unlock_irq(pipe_update_lock);
 
 		timeout = schedule_timeout(timeout);
 
-		local_irq_disable();
+		local_lock_irq(pipe_update_lock);
 	}
 
 	finish_wait(wq, &wait);
@@ -164,7 +167,7 @@ void intel_pipe_update_end(struct intel_crtc *crtc)
 
 	trace_i915_pipe_update_end(crtc, end_vbl_count, scanline_end);
 
-	local_irq_enable();
+	local_unlock_irq(pipe_update_lock);
 
 	if (crtc->debug.start_vbl_count &&
 	    crtc->debug.start_vbl_count != end_vbl_count) {
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 1eca0acac016..99c234ae3f7b 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -1849,6 +1849,7 @@ int radeon_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
 	struct radeon_device *rdev = dev->dev_private;
 
 	/* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */
+	preempt_disable_rt();
 
 	/* Get optional system timestamp before query. */
 	if (stime)
@@ -1941,6 +1942,7 @@ int radeon_get_crtc_scanoutpos(struct drm_device *dev, unsigned int pipe,
 		*etime = ktime_get();
 
 	/* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */
+	preempt_enable_rt();
 
 	/* Decode into vertical and horizontal scanout position. */
 	*vpos = position & 0x1fff;
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index fc836f523afa..c20d23cdf0e6 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1952,10 +1952,10 @@ static int __attach_device(struct iommu_dev_data *dev_data,
 	int ret;
 
 	/*
-	 * Must be called with IRQs disabled. Warn here to detect early
-	 * when its not.
+	 * Must be called with IRQs disabled on a non RT kernel. Warn here to
+	 * detect early when its not.
 	 */
-	WARN_ON(!irqs_disabled());
+	WARN_ON_NONRT(!irqs_disabled());
 
 	/* lock domain */
 	spin_lock(&domain->lock);
@@ -2118,10 +2118,10 @@ static void __detach_device(struct iommu_dev_data *dev_data)
 	struct protection_domain *domain;
 
 	/*
-	 * Must be called with IRQs disabled. Warn here to detect early
-	 * when its not.
+	 * Must be called with IRQs disabled on a non RT kernel. Warn here to
+	 * detect early when its not.
 	 */
-	WARN_ON(!irqs_disabled());
+	WARN_ON_NONRT(!irqs_disabled());
 
 	if (WARN_ON(!dev_data->domain))
 		return;
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index edb5305b9d4d..7d5ee8a13ac6 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1230,7 +1230,7 @@ static int sc16is7xx_probe(struct device *dev,
 
 	/* Setup interrupt */
 	ret = devm_request_irq(dev, irq, sc16is7xx_irq,
-			       IRQF_ONESHOT | flags, dev_name(dev), s);
+			       flags, dev_name(dev), s);
 	if (!ret)
 		return 0;
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9db5500d63d9..5951c495d124 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -24,7 +24,6 @@
 
 #ifdef CONFIG_F2FS_CHECK_FS
 #define f2fs_bug_on(sbi, condition)	BUG_ON(condition)
-#define f2fs_down_write(x, y)	down_write_nest_lock(x, y)
 #else
 #define f2fs_bug_on(sbi, condition)					\
 	do {								\
@@ -33,7 +32,6 @@
 			set_sbi_flag(sbi, SBI_NEED_FSCK);		\
 		}							\
 	} while (0)
-#define f2fs_down_write(x, y)	down_write(x)
 #endif
 
 /*
@@ -959,7 +957,7 @@ static inline void f2fs_unlock_op(struct f2fs_sb_info *sbi)
 
 static inline void f2fs_lock_all(struct f2fs_sb_info *sbi)
 {
-	f2fs_down_write(&sbi->cp_rwsem, &sbi->cp_mutex);
+	down_write(&sbi->cp_rwsem);
 }
 
 static inline void f2fs_unlock_all(struct f2fs_sb_info *sbi)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 60048c50404e..f2cd67624f18 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -694,6 +694,18 @@ static inline void __ftrace_enabled_restore(int enabled)
 #define CALLER_ADDR5 ((unsigned long)ftrace_return_address(5))
 #define CALLER_ADDR6 ((unsigned long)ftrace_return_address(6))
 
+static inline unsigned long get_lock_parent_ip(void)
+{
+	unsigned long addr = CALLER_ADDR0;
+
+	if (!in_lock_functions(addr))
+		return addr;
+	addr = CALLER_ADDR1;
+	if (!in_lock_functions(addr))
+		return addr;
+	return CALLER_ADDR2;
+}
+
 #ifdef CONFIG_IRQSOFF_TRACER
   extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
   extern void time_hardirqs_off(unsigned long a0, unsigned long a1);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b6a2358eb793..58c5ec8c3742 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -183,8 +183,6 @@ extern void update_cpu_load_nohz(void);
 static inline void update_cpu_load_nohz(void) { }
 #endif
 
-extern unsigned long get_parent_ip(unsigned long addr);
-
 extern void dump_cpu_task(int cpu);
 
 struct seq_file;
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index fff846b512e6..253ef2833c46 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -132,7 +132,7 @@ DEFINE_EVENT(writeback_dirty_inode_template, writeback_dirty_inode,
 );
 
 #ifdef CREATE_TRACE_POINTS
-#ifdef CONFIG_CGROUP_WRITEBACK
+#if defined(CONFIG_CGROUP_WRITEBACK) && !defined(CONFIG_PREEMPT_RT_FULL)
 
 static inline size_t __trace_wb_cgroup_size(struct bdi_writeback *wb)
 {
diff --git a/kernel/locking/lglock.c b/kernel/locking/lglock.c
index 51bfe64e7d16..57e0ea72c28a 100644
--- a/kernel/locking/lglock.c
+++ b/kernel/locking/lglock.c
@@ -86,7 +86,7 @@ void lg_double_lock(struct lglock *lg, int cpu1, int cpu2)
 	if (cpu2 < cpu1)
 		swap(cpu1, cpu2);
 
-	preempt_disable();
+	preempt_disable_nort();
 	lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
 	lg_do_lock(per_cpu_ptr(lg->lock, cpu1));
 	lg_do_lock(per_cpu_ptr(lg->lock, cpu2));
@@ -97,7 +97,7 @@ void lg_double_unlock(struct lglock *lg, int cpu1, int cpu2)
 	lock_release(&lg->lock_dep_map, 1, _RET_IP_);
 	lg_do_unlock(per_cpu_ptr(lg->lock, cpu1));
 	lg_do_unlock(per_cpu_ptr(lg->lock, cpu2));
-	preempt_enable();
+	preempt_enable_nort();
 }
 
 void lg_global_lock(struct lglock *lg)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index d89328e260df..5bb3364a6284 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -390,6 +390,7 @@ static struct rcu_torture_ops rcu_ops = {
 	.name		= "rcu"
 };
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 /*
  * Definitions for rcu_bh torture testing.
  */
@@ -429,6 +430,12 @@ static struct rcu_torture_ops rcu_bh_ops = {
 	.name		= "rcu_bh"
 };
 
+#else
+static struct rcu_torture_ops rcu_bh_ops = {
+	.ttype		= INVALID_RCU_FLAVOR,
+};
+#endif
+
 /*
  * Don't even think about trying any of these in real life!!!
  * The names includes "busted", and they really means it!
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e6627288b03d..94827a59301e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3039,16 +3039,6 @@ u64 scheduler_tick_max_deferment(void)
 }
 #endif
 
-notrace unsigned long get_parent_ip(unsigned long addr)
-{
-	if (in_lock_functions(addr)) {
-		addr = CALLER_ADDR2;
-		if (in_lock_functions(addr))
-			addr = CALLER_ADDR3;
-	}
-	return addr;
-}
-
 #if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
 				defined(CONFIG_PREEMPT_TRACER))
 
@@ -3070,7 +3060,7 @@ void preempt_count_add(int val)
 				PREEMPT_MASK - 10);
 #endif
 	if (preempt_count() == val) {
-		unsigned long ip = get_parent_ip(CALLER_ADDR1);
+		unsigned long ip = get_lock_parent_ip();
 #ifdef CONFIG_DEBUG_PREEMPT
 		current->preempt_disable_ip = ip;
 #endif
@@ -3097,7 +3087,7 @@ void preempt_count_sub(int val)
 #endif
 
 	if (preempt_count() == val)
-		trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+		trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
 	__preempt_count_sub(val);
 }
 EXPORT_SYMBOL(preempt_count_sub);
@@ -3469,7 +3459,7 @@ static void __sched notrace preempt_schedule_common(void)
  * 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)
+static __always_inline int preemptible_lazy(void)
 {
 	if (test_thread_flag(TIF_NEED_RESCHED))
 		return 1;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 2ca63cc1469e..cb9c1d5dee10 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -287,9 +287,9 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 
 	if (preempt_count() == cnt) {
 #ifdef CONFIG_DEBUG_PREEMPT
-		current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1);
+		current->preempt_disable_ip = get_lock_parent_ip();
 #endif
-		trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+		trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
 	}
 }
 EXPORT_SYMBOL(__local_bh_disable_ip);
diff --git a/kernel/time/tick-broadcast-hrtimer.c b/kernel/time/tick-broadcast-hrtimer.c
index 53d7184da0be..1b4ac3361c3f 100644
--- a/kernel/time/tick-broadcast-hrtimer.c
+++ b/kernel/time/tick-broadcast-hrtimer.c
@@ -106,5 +106,6 @@ 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);
 }
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 36e584fdf863..069942c22b6b 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -421,13 +421,13 @@ void start_critical_timings(void)
 {
 	if (preempt_trace() || irq_trace())
 		start_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
-	trace_preemptirqsoff_hist(TRACE_START, 1);
+	trace_preemptirqsoff_hist_rcuidle(TRACE_START, 1);
 }
 EXPORT_SYMBOL_GPL(start_critical_timings);
 
 void stop_critical_timings(void)
 {
-	trace_preemptirqsoff_hist(TRACE_STOP, 0);
+	trace_preemptirqsoff_hist_rcuidle(TRACE_STOP, 0);
 	if (preempt_trace() || irq_trace())
 		stop_critical_timing(CALLER_ADDR0, CALLER_ADDR1);
 }
@@ -437,7 +437,7 @@ EXPORT_SYMBOL_GPL(stop_critical_timings);
 #ifdef CONFIG_PROVE_LOCKING
 void time_hardirqs_on(unsigned long a0, unsigned long a1)
 {
-	trace_preemptirqsoff_hist(IRQS_ON, 0);
+	trace_preemptirqsoff_hist_rcuidle(IRQS_ON, 0);
 	if (!preempt_trace() && irq_trace())
 		stop_critical_timing(a0, a1);
 }
@@ -446,7 +446,7 @@ void time_hardirqs_off(unsigned long a0, unsigned long a1)
 {
 	if (!preempt_trace() && irq_trace())
 		start_critical_timing(a0, a1);
-	trace_preemptirqsoff_hist(IRQS_OFF, 1);
+	trace_preemptirqsoff_hist_rcuidle(IRQS_OFF, 1);
 }
 
 #else /* !CONFIG_PROVE_LOCKING */
diff --git a/localversion-rt b/localversion-rt
index 700c857efd9b..22746d6390a4 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt8
+-rt9

Re: [ANNOUNCE] v4.4.3-rt9

[Mike Galbraith]

On Mon, 2016-02-29 at 13:46 +0100, Thomas Gleixner wrote:
> Dear RT folks!
> 
> I'm pleased to announce the v4.4.3-rt9 patch set. v4.4.2-rt7 and v4.4.3-rt8
> are non-announced updates to incorporate the linux-4.4.y stable tree.
> 
> There is one change caused by the 4.4.3 update:
> 
>   The relaxed handling of dump_stack() on RT has been dropped as there is
>   actually a potential deadlock lurking around the corner. See: commit
>   d7ce36924344 upstream. This does not effect the other facilities which
>   gather stack traces.

Hrm.  I had rolled that dropped bit forward as below.  I was given
cause to do a very large pile of ltp oom4 testing (rt kernels will
livelock due to waitqueue workers waiting for kthreadd to get memory to
spawn a kworker thread, while stuck kworker holds manager mutex, unless
workers are run as rt tasks to keep us from getting that depleted in
the first place), which gives it oodles of exercise, and all _seemed_
well.  Only seemed?

--- a/lib/dump_stack.c	2016-02-29 14:20:29.512510444 +0100
+++ b/lib/dump_stack.c	2016-02-26 13:03:15.755297038 +0100
@@ -8,6 +8,7 @@
 #include <linux/sched.h>
 #include <linux/smp.h>
 #include <linux/atomic.h>
+#include <linux/locallock.h>
 
 static void __dump_stack(void)
 {
@@ -22,6 +23,7 @@ static void __dump_stack(void)
  */
 #ifdef CONFIG_SMP
 static atomic_t dump_lock = ATOMIC_INIT(-1);
+static DEFINE_LOCAL_IRQ_LOCK(dump_stack_irq_lock);
 
 asmlinkage __visible void dump_stack(void)
 {
@@ -35,7 +37,7 @@ asmlinkage __visible void dump_stack(voi
 	 * against other CPUs
 	 */
 retry:
-	local_irq_save(flags);
+	local_lock_irqsave(dump_stack_irq_lock, flags);
 	cpu = smp_processor_id();
 	old = atomic_cmpxchg(&dump_lock, -1, cpu);
 	if (old == -1) {
@@ -43,7 +45,7 @@ retry:
 	} else if (old == cpu) {
 		was_locked = 1;
 	} else {
-		local_irq_restore(flags);
+		local_unlock_irqrestore(dump_stack_irq_lock, flags);
 		cpu_relax();
 		goto retry;
 	}
@@ -53,7 +55,7 @@ retry:
 	if (!was_locked)
 		atomic_set(&dump_lock, -1);
 
-	local_irq_restore(flags);
+	local_unlock_irqrestore(dump_stack_irq_lock, flags);
 }
 #else
 asmlinkage __visible void dump_stack(void)

Re: [ANNOUNCE] v4.4.3-rt9

[Thomas Gleixner]

On Mon, 29 Feb 2016, Mike Galbraith wrote:

> On Mon, 2016-02-29 at 13:46 +0100, Thomas Gleixner wrote:
> > Dear RT folks!
> > 
> > I'm pleased to announce the v4.4.3-rt9 patch set. v4.4.2-rt7 and v4.4.3-rt8
> > are non-announced updates to incorporate the linux-4.4.y stable tree.
> > 
> > There is one change caused by the 4.4.3 update:
> > 
> >   The relaxed handling of dump_stack() on RT has been dropped as there is
> >   actually a potential deadlock lurking around the corner. See: commit
> >   d7ce36924344 upstream. This does not effect the other facilities which
> >   gather stack traces.
> 
> Hrm.  I had rolled that dropped bit forward as below.  I was given
> cause to do a very large pile of ltp oom4 testing (rt kernels will
> livelock due to waitqueue workers waiting for kthreadd to get memory to
> spawn a kworker thread, while stuck kworker holds manager mutex, unless
> workers are run as rt tasks to keep us from getting that depleted in
> the first place), which gives it oodles of exercise, and all _seemed_
> well.  Only seemed?

Well, it will work nicely as long as you don't trigger a back trace in hard
irq context. Hmm?

Thanks,

	tglx

Re: [ANNOUNCE] v4.4.3-rt9

[Mike Galbraith]

On Mon, 2016-02-29 at 16:00 +0100, Thomas Gleixner wrote:
> On Mon, 29 Feb 2016, Mike Galbraith wrote:
> 
> > On Mon, 2016-02-29 at 13:46 +0100, Thomas Gleixner wrote:
> > > Dear RT folks!
> > > 
> > > I'm pleased to announce the v4.4.3-rt9 patch set. v4.4.2-rt7 and v4.4.3-rt8
> > > are non-announced updates to incorporate the linux-4.4.y stable tree.
> > > 
> > > There is one change caused by the 4.4.3 update:
> > > 
> > >   The relaxed handling of dump_stack() on RT has been dropped as there is
> > >   actually a potential deadlock lurking around the corner. See: commit
> > >   d7ce36924344 upstream. This does not effect the other facilities which
> > >   gather stack traces.
> > 
> > Hrm.  I had rolled that dropped bit forward as below.  I was given
> > cause to do a very large pile of ltp oom4 testing (rt kernels will
> > livelock due to waitqueue workers waiting for kthreadd to get memory to
> > spawn a kworker thread, while stuck kworker holds manager mutex, unless
> > workers are run as rt tasks to keep us from getting that depleted in
> > the first place), which gives it oodles of exercise, and all _seemed_
> > well.  Only seemed?
> 
> Well, it will work nicely as long as you don't trigger a back trace in hard
> irq context. Hmm?

Poo.. that's a pretty darn good reason.  Thanks.

	-Mike

Re: [ANNOUNCE] v4.4.3-rt9

[Steven Rostedt]

On Mon, 29 Feb 2016 13:46:50 +0100 (CET)
Thomas Gleixner <tglx@linutronix.de> wrote:

> You can get this release via the git tree at:
> 
>     git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.4.3-rt9
> 

There is no v4.4.3-rt9 tag. There's v4.4.3-rt9-patches and
v4.4.3-rt9-rebase, but v4.4.3-rt9 is missing.

-- Steve

Re: [ANNOUNCE] v4.4.3-rt9

[Thomas Gleixner]

On Mon, 29 Feb 2016, Steven Rostedt wrote:
> On Mon, 29 Feb 2016 13:46:50 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
> 
> > You can get this release via the git tree at:
> > 
> >     git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.4.3-rt9
> > 
> 
> There is no v4.4.3-rt9 tag. There's v4.4.3-rt9-patches and
> v4.4.3-rt9-rebase, but v4.4.3-rt9 is missing.

Hmm, pushed with --follow-tags but this time it needed a manual tag
push. Weird.

Thanks,

	tglx