[PATCH RT 0/4] Linux 3.14.34-rt32-rc2

[PATCH RT 0/4] Linux 3.14.34-rt32-rc2

[Steven Rostedt]

Dear RT Folks,

This is the RT stable review cycle of patch 3.14.34-rt32-rc2.

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 3/20/2015.

I'm only posting the patches that were added since rc1.

Enjoy,

-- Steve


To build 3.14.34-rt32-rc2 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v3.x/linux-3.14.tar.xz

  http://www.kernel.org/pub/linux/kernel/v3.x/patch-3.14.34.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/3.14/patch-3.14.34-rt32-rc2.patch.xz

You can also build from 3.14.34-rt31 by applying the incremental patch:

http://www.kernel.org/pub/linux/kernel/projects/rt/3.14/incr/patch-3.14.34-rt31-rt32-rc2.patch.xz


Changes from 3.14.34-rt31:

---


Brad Mouring (1):
      rtmutex.c: Fix incorrect waiter check

Daniel Wagner (2):
      work-simple: Simple work queue implemenation
      thermal: Defer thermal wakups to threads

Gustavo Bittencourt (1):
      rtmutex: enable deadlock detection in ww_mutex_lock functions

Josh Cartwright (1):
      lockdep: selftest: fix warnings due to missing PREEMPT_RT conditionals

Kevin Hao (1):
      netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y

Mike Galbraith (6):
      rt,locking: fix __ww_mutex_lock_interruptible() lockdep annotation
      x86: UV: raw_spinlock conversion
      scheduling while atomic in cgroup code
      sunrpc: make svc_xprt_do_enqueue() use get_cpu_light()
      locking: ww_mutex: fix ww_mutex vs self-deadlock
      fs,btrfs: fix rt deadlock on extent_buffer->lock

Paul E. McKenney (4):
      timers: Track total number of timers in list
      timers: Reduce __run_timers() latency for empty list
      timers: Reduce future __run_timers() latency for newly emptied list
      timers: Reduce future __run_timers() latency for first add to empty list

Paul Gortmaker (1):
      sas-ata/isci: dont't disable interrupts in qc_issue handler

Sebastian Andrzej Siewior (5):
      gpio: omap: use raw locks for locking
      locking/rt-mutex: avoid a NULL pointer dereference on deadlock
      arm/futex: disable preemption during futex_atomic_cmpxchg_inatomic()
      Revert "rwsem-rt: Do not allow readers to nest"
      fs/aio: simple simple work

Steven Rostedt (Red Hat) (3):
      staging: Mark rtl8821ae as broken
      Revert "timers: do not raise softirq unconditionally"
      Linux 3.14.34-rt32-rc2

Thomas Gleixner (14):
      rtmutex: Simplify rtmutex_slowtrylock()
      rtmutex: Simplify and document try_to_take_rtmutex()
      rtmutex: No need to keep task ref for lock owner check
      rtmutex: Clarify the boost/deboost part
      rtmutex: Document pi chain walk
      rtmutex: Simplify remove_waiter()
      rtmutex: Confine deadlock logic to futex
      rtmutex: Cleanup deadlock detector debug logic
      rtmutex: Avoid pointless requeueing in the deadlock detection chain walk
      futex: Make unlock_pi more robust
      futex: Use futex_top_waiter() in lookup_pi_state()
      futex: Split out the waiter check from lookup_pi_state()
      futex: Split out the first waiter attachment from lookup_pi_state()
      futex: Simplify futex_lock_pi_atomic() and make it more robust

Yadi.hu (1):
      ARM: enable irq in translation/section permission fault handlers

Yang Shi (1):
      mips: rt: Replace pagefault_* to raw version

Yong Zhang (1):
      ARM: cmpxchg: define __HAVE_ARCH_CMPXCHG for armv6 and later

----
 arch/arm/include/asm/cmpxchg.h         |   2 +
 arch/arm/include/asm/futex.h           |   4 +
 arch/arm/mm/fault.c                    |   6 +
 arch/mips/mm/init.c                    |   4 +-
 arch/x86/include/asm/uv/uv_bau.h       |  14 +-
 arch/x86/include/asm/uv/uv_hub.h       |   2 +-
 arch/x86/kernel/apic/x2apic_uv_x.c     |   2 +-
 arch/x86/platform/uv/tlb_uv.c          |  26 +-
 arch/x86/platform/uv/uv_time.c         |  21 +-
 drivers/gpio/gpio-omap.c               |  72 ++--
 drivers/scsi/libsas/sas_ata.c          |   4 +-
 drivers/staging/rtl8821ae/Kconfig      |   1 +
 drivers/thermal/x86_pkg_temp_thermal.c |  50 ++-
 fs/aio.c                               |  24 +-
 fs/btrfs/ctree.c                       |   4 +-
 fs/btrfs/extent-tree.c                 |   8 -
 include/linux/hrtimer.h                |   3 +-
 include/linux/netpoll.h                |  16 +-
 include/linux/rtmutex.h                |   8 +-
 include/linux/rwsem_rt.h               |   1 +
 include/linux/work-simple.h            |  24 ++
 kernel/futex.c                         | 402 +++++++++++------------
 kernel/hrtimer.c                       |  31 +-
 kernel/locking/rt.c                    |  37 ++-
 kernel/locking/rtmutex-debug.c         |   5 +-
 kernel/locking/rtmutex-debug.h         |   7 +-
 kernel/locking/rtmutex-tester.c        |   4 +-
 kernel/locking/rtmutex.c               | 582 ++++++++++++++++++++++++---------
 kernel/locking/rtmutex.h               |   7 +-
 kernel/locking/rtmutex_common.h        |  22 +-
 kernel/sched/Makefile                  |   2 +-
 kernel/sched/work-simple.c             | 172 ++++++++++
 kernel/timer.c                         |  72 ++--
 lib/locking-selftest.c                 |  27 ++
 localversion-rt                        |   2 +-
 mm/memcontrol.c                        |   7 +-
 net/sunrpc/svc_xprt.c                  |   4 +-
 37 files changed, 1133 insertions(+), 546 deletions(-)

[PATCH RT 1/4] fs,btrfs: fix rt deadlock on extent_buffer->lock

[Steven Rostedt]

[-- Attachment #1: 0039-fs-btrfs-fix-rt-deadlock-on-extent_buffer-lock.patch --]
[-- Type: text/plain, Size: 2695 bytes --]

3.14.34-rt32-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: Mike Galbraith <mgalbraith@suse.de>

Sat Jul 14 12:30:41 CEST 2012

Trivially repeatable deadlock is cured by enabling lockdep code in
btrfs_clear_path_blocking() as suggested by Chris Mason.  He also
suggested restricting blocking reader count to one, and not allowing
a spinning reader while blocking reader exists.  This has proven to
be unnecessary, the strict lock order enforcement is enough.. or
rather that's my box's opinion after long hours of hard pounding.

Note: extent-tree.c bit is additional recommendation from Chris
      Mason, split into a separate patch after discussion.

Link: http://lkml.kernel.org/r/1414913478.5380.114.camel@marge.simpson.net

Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Clark Williams <williams@redhat.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 fs/btrfs/ctree.c       | 4 ++--
 fs/btrfs/extent-tree.c | 8 --------
 2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cbd3a7d6fa68..50c7edc8f4d2 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -80,7 +80,7 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
 {
 	int i;
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#if (defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_PREEMPT_RT_BASE))
 	/* lockdep really cares that we take all of these spinlocks
 	 * in the right order.  If any of the locks in the path are not
 	 * currently blocking, it is going to complain.  So, make really
@@ -107,7 +107,7 @@ noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
 		}
 	}
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#if (defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_PREEMPT_RT_BASE))
 	if (held)
 		btrfs_clear_lock_blocking_rw(held, held_rw);
 #endif
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d2f1c011d73a..73035cf6681a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6940,14 +6940,6 @@ again:
 		goto again;
 	}
 
-	if (btrfs_test_opt(root, ENOSPC_DEBUG)) {
-		static DEFINE_RATELIMIT_STATE(_rs,
-				DEFAULT_RATELIMIT_INTERVAL * 10,
-				/*DEFAULT_RATELIMIT_BURST*/ 1);
-		if (__ratelimit(&_rs))
-			WARN(1, KERN_DEBUG
-				"BTRFS: block rsv returned %d\n", ret);
-	}
 try_reserve:
 	ret = reserve_metadata_bytes(root, block_rsv, blocksize,
 				     BTRFS_RESERVE_NO_FLUSH);
-- 
2.1.4

[PATCH RT 2/4] Revert "timers: do not raise softirq unconditionally"

[Steven Rostedt]

[-- Attachment #1: 0040-Revert-timers-do-not-raise-softirq-unconditionally.patch --]
[-- Type: text/plain, Size: 4460 bytes --]

3.14.34-rt32-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

This reverts commit 891f510568343d93c5aa2f477b6bebe009b48f05.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Conflicts:
	kernel/timer.c
---
 include/linux/hrtimer.h |  3 ++-
 kernel/hrtimer.c        | 31 ++++++++++++++++++++++++-------
 kernel/timer.c          | 46 ++--------------------------------------------
 3 files changed, 28 insertions(+), 52 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index bdbf77db0f4d..79a7a35e1a6e 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -461,8 +461,9 @@ extern int schedule_hrtimeout_range_clock(ktime_t *expires,
 		unsigned long delta, const enum hrtimer_mode mode, int clock);
 extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
 
-/* Called from the periodic timer tick */
+/* Soft interrupt function to run the hrtimer queues: */
 extern void hrtimer_run_queues(void);
+extern void hrtimer_run_pending(void);
 
 /* Bootup initialization: */
 extern void __init hrtimers_init(void);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f97b9f65c5fa..164201aba52f 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1717,6 +1717,30 @@ static void run_hrtimer_softirq(struct softirq_action *h)
 }
 
 /*
+ * Called from timer softirq every jiffy, expire hrtimers:
+ *
+ * For HRT its the fall back code to run the softirq in the timer
+ * softirq context in case the hrtimer initialization failed or has
+ * not been done yet.
+ */
+void hrtimer_run_pending(void)
+{
+	if (hrtimer_hres_active())
+		return;
+
+	/*
+	 * This _is_ ugly: We have to check in the softirq context,
+	 * whether we can switch to highres and / or nohz mode. The
+	 * clocksource switch happens in the timer interrupt with
+	 * xtime_lock held. Notification from there only sets the
+	 * check bit in the tick_oneshot code, otherwise we might
+	 * deadlock vs. xtime_lock.
+	 */
+	if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
+		hrtimer_switch_to_hres();
+}
+
+/*
  * Called from hardirq context every jiffy
  */
 void hrtimer_run_queues(void)
@@ -1729,13 +1753,6 @@ void hrtimer_run_queues(void)
 	if (hrtimer_hres_active())
 		return;
 
-	/*
-	 * Check whether we can switch to highres mode.
-	 */
-	if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())
-	    && hrtimer_switch_to_hres())
-		return;
-
 	for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
 		base = &cpu_base->clock_base[index];
 		if (!timerqueue_getnext(&base->active))
diff --git a/kernel/timer.c b/kernel/timer.c
index 2059f6b27595..34fd2dbba3e3 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1464,6 +1464,8 @@ static void run_timer_softirq(struct softirq_action *h)
 {
 	struct tvec_base *base = __this_cpu_read(tvec_bases);
 
+	hrtimer_run_pending();
+
 #if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
 	irq_work_run();
 #endif
@@ -1477,52 +1479,8 @@ static void run_timer_softirq(struct softirq_action *h)
  */
 void run_local_timers(void)
 {
-	struct tvec_base *base = __this_cpu_read(tvec_bases);
-
 	hrtimer_run_queues();
-	/*
-	 * We can access this lockless as we are in the timer
-	 * interrupt. If there are no timers queued, nothing to do in
-	 * the timer softirq.
-	 */
-#ifdef CONFIG_PREEMPT_RT_FULL
-
-#ifndef CONFIG_SMP
-	/*
-	 * The spin_do_trylock() later may fail as the lock may be hold before
-	 * the interrupt arrived. The spin-lock debugging code will raise a
-	 * warning if the try_lock fails on UP. Since this is only an
-	 * optimization for the FULL_NO_HZ case (not to run the timer softirq on
-	 * an nohz_full CPU) we don't really care and shedule the softirq.
-	 */
 	raise_softirq(TIMER_SOFTIRQ);
-	return;
-#endif
-
-	/* On RT, irq work runs from softirq */
-	if (irq_work_needs_cpu()) {
-		raise_softirq(TIMER_SOFTIRQ);
-		return;
-	}
-
-	if (!spin_do_trylock(&base->lock)) {
-		raise_softirq(TIMER_SOFTIRQ);
-		return;
-	}
-#endif
-
-	if (!base->active_timers)
-		goto out;
-
-	/* Check whether the next pending timer has expired */
-	if (time_before_eq(base->next_timer, jiffies))
-		raise_softirq(TIMER_SOFTIRQ);
-out:
-#ifdef CONFIG_PREEMPT_RT_FULL
-	rt_spin_unlock_after_trylock_in_irq(&base->lock);
-#endif
-	/* The ; ensures that gcc won't complain in the !RT case */
-	;
 }
 
 #ifdef __ARCH_WANT_SYS_ALARM
-- 
2.1.4

[PATCH RT 3/4] netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y

[Steven Rostedt]

[-- Attachment #1: 0041-netpoll-guard-the-access-to-dev-npinfo-with-rcu_read.patch --]
[-- Type: text/plain, Size: 3243 bytes --]

3.14.34-rt32-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: Kevin Hao <haokexin@gmail.com>

For vanilla kernel we don't need to invoke rcu_read_lock/unlock_bh
explicitly to mark an RCU-bh critical section in the softirq context
because bh is already disabled in this case. But for a rt kernel,
the commit ("rcu: Merge RCU-bh into RCU-preempt") implements the
RCU-bh in term of RCU-preempt. So we have to use
rcu_read_lock/unlock_bh() to mark an RCU-bh critical section even in
a softirq context. Otherwise we will get a call trace like this:
  include/linux/netpoll.h:90 suspicious rcu_dereference_check() usage!
  other info that might help us debug this:
  rcu_scheduler_active = 1, debug_locks = 0
  1 lock held by irq/177-eth0_g0/129:
   #0:  (&per_cpu(local_softirq_locks[i], __cpu).lock){+.+...}, at: [<8002f544>] do_current_softirqs+0x12c/0x5ec

  stack backtrace:
  CPU: 0 PID: 129 Comm: irq/177-eth0_g0 Not tainted 3.14.23 #11
  [<80018c0c>] (unwind_backtrace) from [<800138b0>] (show_stack+0x20/0x24)
  [<800138b0>] (show_stack) from [<8075c3bc>] (dump_stack+0x84/0xd0)
  [<8075c3bc>] (dump_stack) from [<8008111c>] (lockdep_rcu_suspicious+0xe8/0x11c)
  [<8008111c>] (lockdep_rcu_suspicious) from [<805e94e8>] (dev_gro_receive+0x240/0x724)
  [<805e94e8>] (dev_gro_receive) from [<805e9c34>] (napi_gro_receive+0x3c/0x1e8)
  [<805e9c34>] (napi_gro_receive) from [<804b01ac>] (gfar_clean_rx_ring+0x2d4/0x624)
  [<804b01ac>] (gfar_clean_rx_ring) from [<804b078c>] (gfar_poll_rx_sq+0x58/0xe8)
  [<804b078c>] (gfar_poll_rx_sq) from [<805eada8>] (net_rx_action+0x1c8/0x418)
  [<805eada8>] (net_rx_action) from [<8002f62c>] (do_current_softirqs+0x214/0x5ec)
  [<8002f62c>] (do_current_softirqs) from [<8002fa88>] (__local_bh_enable+0x84/0x9c)
  [<8002fa88>] (__local_bh_enable) from [<8002fab8>] (local_bh_enable+0x18/0x1c)
  [<8002fab8>] (local_bh_enable) from [<80093924>] (irq_forced_thread_fn+0x50/0x74)
  [<80093924>] (irq_forced_thread_fn) from [<80093c30>] (irq_thread+0x158/0x1c4)
  [<80093c30>] (irq_thread) from [<800555b8>] (kthread+0xd4/0xe8)
  [<800555b8>] (kthread) from [<8000ee88>] (ret_from_fork+0x14/0x20)

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 include/linux/netpoll.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index fbfdb9d8d3a7..039dd5df0ef7 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -87,9 +87,21 @@ static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 #ifdef CONFIG_NETPOLL
 static inline bool netpoll_rx_on(struct sk_buff *skb)
 {
-	struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	struct netpoll_info *npinfo;
+	bool ret;
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_lock_bh();
+#endif
+
+	npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	ret = npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_unlock_bh();
+#endif
 
-	return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+	return ret;
 }
 
 static inline bool netpoll_rx(struct sk_buff *skb)
-- 
2.1.4

[PATCH RT 4/4] Linux 3.14.34-rt32-rc2

[Steven Rostedt]

[-- Attachment #1: 0042-Linux-3.14.34-rt32-rc2.patch --]
[-- Type: text/plain, Size: 414 bytes --]

3.14.34-rt32-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

---
 localversion-rt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/localversion-rt b/localversion-rt
index a68b4337d4ce..b9cdd26a5bd9 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt31
+-rt32-rc2
-- 
2.1.4

[PATCH RT 3/4] netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y

[Steven Rostedt]

[-- Attachment #1: 0033-netpoll-guard-the-access-to-dev-npinfo-with-rcu_read.patch --]
[-- Type: text/plain, Size: 3243 bytes --]

3.10.70-rt75-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: Kevin Hao <haokexin@gmail.com>

For vanilla kernel we don't need to invoke rcu_read_lock/unlock_bh
explicitly to mark an RCU-bh critical section in the softirq context
because bh is already disabled in this case. But for a rt kernel,
the commit ("rcu: Merge RCU-bh into RCU-preempt") implements the
RCU-bh in term of RCU-preempt. So we have to use
rcu_read_lock/unlock_bh() to mark an RCU-bh critical section even in
a softirq context. Otherwise we will get a call trace like this:
  include/linux/netpoll.h:90 suspicious rcu_dereference_check() usage!
  other info that might help us debug this:
  rcu_scheduler_active = 1, debug_locks = 0
  1 lock held by irq/177-eth0_g0/129:
   #0:  (&per_cpu(local_softirq_locks[i], __cpu).lock){+.+...}, at: [<8002f544>] do_current_softirqs+0x12c/0x5ec

  stack backtrace:
  CPU: 0 PID: 129 Comm: irq/177-eth0_g0 Not tainted 3.14.23 #11
  [<80018c0c>] (unwind_backtrace) from [<800138b0>] (show_stack+0x20/0x24)
  [<800138b0>] (show_stack) from [<8075c3bc>] (dump_stack+0x84/0xd0)
  [<8075c3bc>] (dump_stack) from [<8008111c>] (lockdep_rcu_suspicious+0xe8/0x11c)
  [<8008111c>] (lockdep_rcu_suspicious) from [<805e94e8>] (dev_gro_receive+0x240/0x724)
  [<805e94e8>] (dev_gro_receive) from [<805e9c34>] (napi_gro_receive+0x3c/0x1e8)
  [<805e9c34>] (napi_gro_receive) from [<804b01ac>] (gfar_clean_rx_ring+0x2d4/0x624)
  [<804b01ac>] (gfar_clean_rx_ring) from [<804b078c>] (gfar_poll_rx_sq+0x58/0xe8)
  [<804b078c>] (gfar_poll_rx_sq) from [<805eada8>] (net_rx_action+0x1c8/0x418)
  [<805eada8>] (net_rx_action) from [<8002f62c>] (do_current_softirqs+0x214/0x5ec)
  [<8002f62c>] (do_current_softirqs) from [<8002fa88>] (__local_bh_enable+0x84/0x9c)
  [<8002fa88>] (__local_bh_enable) from [<8002fab8>] (local_bh_enable+0x18/0x1c)
  [<8002fab8>] (local_bh_enable) from [<80093924>] (irq_forced_thread_fn+0x50/0x74)
  [<80093924>] (irq_forced_thread_fn) from [<80093c30>] (irq_thread+0x158/0x1c4)
  [<80093c30>] (irq_thread) from [<800555b8>] (kthread+0xd4/0xe8)
  [<800555b8>] (kthread) from [<8000ee88>] (ret_from_fork+0x14/0x20)

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 include/linux/netpoll.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index fa2cb76a7029..c1e80c6272aa 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -86,9 +86,21 @@ static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 #ifdef CONFIG_NETPOLL
 static inline bool netpoll_rx_on(struct sk_buff *skb)
 {
-	struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	struct netpoll_info *npinfo;
+	bool ret;
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_lock_bh();
+#endif
+
+	npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	ret = npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_unlock_bh();
+#endif
 
-	return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+	return ret;
 }
 
 static inline bool netpoll_rx(struct sk_buff *skb)
-- 
2.1.4

[PATCH RT 3/4] netpoll: guard the access to dev->npinfo with rcu_read_lock/unlock_bh() for CONFIG_PREEMPT_RT_FULL=y

[Steven Rostedt]

[-- Attachment #1: 0038-netpoll-guard-the-access-to-dev-npinfo-with-rcu_read.patch --]
[-- Type: text/plain, Size: 3243 bytes --]

3.12.38-rt53-rc2 stable review patch.
If anyone has any objections, please let me know.

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

From: Kevin Hao <haokexin@gmail.com>

For vanilla kernel we don't need to invoke rcu_read_lock/unlock_bh
explicitly to mark an RCU-bh critical section in the softirq context
because bh is already disabled in this case. But for a rt kernel,
the commit ("rcu: Merge RCU-bh into RCU-preempt") implements the
RCU-bh in term of RCU-preempt. So we have to use
rcu_read_lock/unlock_bh() to mark an RCU-bh critical section even in
a softirq context. Otherwise we will get a call trace like this:
  include/linux/netpoll.h:90 suspicious rcu_dereference_check() usage!
  other info that might help us debug this:
  rcu_scheduler_active = 1, debug_locks = 0
  1 lock held by irq/177-eth0_g0/129:
   #0:  (&per_cpu(local_softirq_locks[i], __cpu).lock){+.+...}, at: [<8002f544>] do_current_softirqs+0x12c/0x5ec

  stack backtrace:
  CPU: 0 PID: 129 Comm: irq/177-eth0_g0 Not tainted 3.14.23 #11
  [<80018c0c>] (unwind_backtrace) from [<800138b0>] (show_stack+0x20/0x24)
  [<800138b0>] (show_stack) from [<8075c3bc>] (dump_stack+0x84/0xd0)
  [<8075c3bc>] (dump_stack) from [<8008111c>] (lockdep_rcu_suspicious+0xe8/0x11c)
  [<8008111c>] (lockdep_rcu_suspicious) from [<805e94e8>] (dev_gro_receive+0x240/0x724)
  [<805e94e8>] (dev_gro_receive) from [<805e9c34>] (napi_gro_receive+0x3c/0x1e8)
  [<805e9c34>] (napi_gro_receive) from [<804b01ac>] (gfar_clean_rx_ring+0x2d4/0x624)
  [<804b01ac>] (gfar_clean_rx_ring) from [<804b078c>] (gfar_poll_rx_sq+0x58/0xe8)
  [<804b078c>] (gfar_poll_rx_sq) from [<805eada8>] (net_rx_action+0x1c8/0x418)
  [<805eada8>] (net_rx_action) from [<8002f62c>] (do_current_softirqs+0x214/0x5ec)
  [<8002f62c>] (do_current_softirqs) from [<8002fa88>] (__local_bh_enable+0x84/0x9c)
  [<8002fa88>] (__local_bh_enable) from [<8002fab8>] (local_bh_enable+0x18/0x1c)
  [<8002fab8>] (local_bh_enable) from [<80093924>] (irq_forced_thread_fn+0x50/0x74)
  [<80093924>] (irq_forced_thread_fn) from [<80093c30>] (irq_thread+0x158/0x1c4)
  [<80093c30>] (irq_thread) from [<800555b8>] (kthread+0xd4/0xe8)
  [<800555b8>] (kthread) from [<8000ee88>] (ret_from_fork+0x14/0x20)

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 include/linux/netpoll.h | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index f3c7c24bec1c..5a77fc924892 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -86,9 +86,21 @@ static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 #ifdef CONFIG_NETPOLL
 static inline bool netpoll_rx_on(struct sk_buff *skb)
 {
-	struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	struct netpoll_info *npinfo;
+	bool ret;
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_lock_bh();
+#endif
+
+	npinfo = rcu_dereference_bh(skb->dev->npinfo);
+	ret = npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+
+#ifdef CONFIG_PREEMPT_RT_FULL
+	rcu_read_unlock_bh();
+#endif
 
-	return npinfo && (!list_empty(&npinfo->rx_np) || npinfo->rx_flags);
+	return ret;
 }
 
 static inline bool netpoll_rx(struct sk_buff *skb)
-- 
2.1.4