linux.git/kernel, branch v4.3-rc7

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2015-10-23T13:31:39+00:00

Pull scheduler fixes from Ingo Molnar:
 "Misc fixes all around the map: an instrumentation fix, a nohz
  usability fix, a lockdep annotation fix and two task group scheduling
  fixes"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Add missing lockdep_unpin() annotations
  sched/deadline: Fix migration of SCHED_DEADLINE tasks
  nohz: Revert "nohz: Set isolcpus when nohz_full is set"
  sched/fair: Update task group's load_avg after task migration
  sched/fair: Fix overly small weight for interactive group entities
  sched, tracing: Stop/start critical timings around the idle=poll idle loop

Merge branch 'akpm' (patches from Andrew)

2015-10-23T13:10:51+00:00

Merge fixes from Andrew Morton:
 "9 fixes"

* emailed patches from Andrew Morton :
  ocfs2/dlm: unlock lockres spinlock before dlm_lockres_put
  fault-inject: fix inverted interval/probability values in printk
  lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y
  mm: make sendfile(2) killable
  thp: use is_zero_pfn() only after pte_present() check
  mailmap: update Javier Martinez Canillas' email
  MAINTAINERS: add Sergey as zsmalloc reviewer
  mm: cma: fix incorrect type conversion for size during dma allocation
  kmod: don't run async usermode helper as a child of kworker thread

sched/core: Add missing lockdep_unpin() annotations

2015-10-23T10:02:10+00:00

Luca and Wanpeng reported two missing annotations that led to
false lockdep complaints. Add the missing annotations.

Reported-by: Luca Abeni 
Reported-by: Wanpeng Li 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: cbce1a686700 ("sched,lockdep: Employ lock pinning")
Link: http://lkml.kernel.org/r/20151023095008.GY17308@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar

kmod: don't run async usermode helper as a child of kworker thread

2015-10-23T08:55:10+00:00

call_usermodehelper_exec_sync() does fork() + wait() with "unignored"
SIGCHLD.  What we have missed is that this worker thread can have other
children previously forked by call_usermodehelper_exec_work() without
UMH_WAIT_PROC.  If such a child exits in between it becomes a zombie
because auto-reaping only works if SIGCHLD is ignored, and nobody can
reap it (unless/until this worker thread exits too).

Change the !UMH_WAIT_PROC case to use CLONE_PARENT.

Note: this is only first step.  All PF_KTHREAD tasks, even created by
kernel_thread() should have ->parent == kthreadd by default.

Fixes: bb304a5c6fc63d8506c ("kmod: handle UMH_WAIT_PROC from system unbound workqueue")
Signed-off-by: Oleg Nesterov 
Acked-by: Frederic Weisbecker 
Cc: Rik van Riel 
Cc: Christoph Lameter 
Cc: Tejun Heo 
Cc: Rusty Russell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tracing: Do not allow stack_tracer to record stack in NMI

2015-10-21T01:52:23+00:00

The code in stack tracer should not be executed within an NMI as it grabs
spinlocks and stack tracing an NMI gives the possibility of causing a
deadlock. Although this is safe on x86_64, because it does not perform stack
traces when the task struct stack is not in use (interrupts and NMIs), it
may be an issue for NMIs on i386 and other archs that use the same stack as
the NMI.

Signed-off-by: Steven Rostedt

tracing: Have stack tracer force RCU to be watching

2015-10-20T15:38:08+00:00

The stack tracer was triggering the WARN_ON() in module.c:

 static void module_assert_mutex_or_preempt(void)
 {
 #ifdef CONFIG_LOCKDEP
	if (unlikely(!debug_locks))
		return;

	WARN_ON(!rcu_read_lock_sched_held() &&
		!lockdep_is_held(&module_mutex));
 #endif
 }

The reason is that the stack tracer traces all function calls, and some of
those calls happen while exiting or entering user space and idle. Some of
these functions are called after RCU had already stopped watching, as RCU
does not watch userspace or idle CPUs.

If a max stack is hit, then the save_stack_trace() is called, which will
check module addresses and call module_assert_mutex_or_preempt(), and then
trigger the warning. Sad part is, the warning itself will also do a stack
trace and tigger the same warning. That probably should be fixed.

The warning was added by 0be964be0d45 "module: Sanitize RCU usage and
locking" but this bug has probably been around longer. But it's unlikely to
cause much harm, but the new warning causes the system to lock up.

Cc: stable@vger.kernel.org # 4.2+
Cc: Peter Zijlstra 
Cc:"Paul E. McKenney" 
Signed-off-by: Steven Rostedt

sched/deadline: Fix migration of SCHED_DEADLINE tasks

2015-10-20T08:13:36+00:00

Commit:

  9d5142624256 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")

broke select_task_rq_dl() and find_lock_later_rq(), because it introduced
a comparison between the local task's deadline and dl.earliest_dl.curr of
the remote queue.

However, if the remote runqueue does not contain any SCHED_DEADLINE
task its earliest_dl.curr is 0 (always smaller than the deadline of
the local task) and the remote runqueue is not selected for pushing.

As a result, if an application creates multiple SCHED_DEADLINE
threads, they will never be pushed to runqueues that do not already
contain SCHED_DEADLINE tasks.

This patch fixes the issue by checking if dl.dl_nr_running == 0.

Signed-off-by: Luca Abeni 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Wanpeng Li 
Fixes: 9d5142624256 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")
Link: http://lkml.kernel.org/r/1444982781-15608-1-git-send-email-luca.abeni@unitn.it
Signed-off-by: Ingo Molnar

nohz: Revert "nohz: Set isolcpus when nohz_full is set"

2015-10-20T08:13:36+00:00

This reverts:

  8cb9764fc88b ("nohz: Set isolcpus when nohz_full is set")

We assumed that full-nohz users always want scheduler isolation on full
dynticks CPUs, therefore we included full-nohz CPUs on cpu_isolated_map.

This means that tasks run by default on CPUs outside the nohz_full range
unless their affinity is explicity overwritten.

This suits pure isolation workloads but when the machine is needed to
run common workloads, the available sets of CPUs to run common tasks
becomes reduced.

We reach an extreme case when CONFIG_NO_HZ_FULL_ALL is enabled as it
leaves only CPU 0 for non-isolation tasks, which makes people think that
their supercomputer regressed to 90's UP - which is true in a sense.

Some full-nohz users appear to be interested in running normal workloads
either before or after an isolation workload. Full-nohz isn't optimized
toward normal workloads but it's still better than UP performance.

We are reaching a limitation in kernel presets here. Lets revert this
cpu_isolated_map inclusion and let userspace do its own scheduler
isolation using cpusets or explicit affinity settings.

Reported-by: Ingo Molnar 
Reported-by: Mike Galbraith 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Thomas Gleixner 
Cc: Alexey Dobriyan 
Cc: Andrew Morton 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Dave Jones 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Oleg Nesterov 
Cc: Paul E . McKenney 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Link: http://lkml.kernel.org/r/1444663283-30068-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

sched/fair: Update task group's load_avg after task migration

2015-10-20T08:13:35+00:00

When cfs_rq has cfs_rq->removed_load_avg set (when a task migrates from
this cfs_rq), we need to update its contribution to the group's load_avg.

This should not increase tg's update too much, because in most cases, the
cfs_rq has already decayed its load_avg.

Tested-by: Dietmar Eggemann 
Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Dietmar Eggemann 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1444699103-20272-2-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar

sched/fair: Fix overly small weight for interactive group entities

2015-10-20T08:13:34+00:00

Commit:

  9d89c257dfb9 ("sched/fair: Rewrite runnable load and utilization average tracking")

led to an overly small weight for interactive group entities. The bad case
can be easily reproduced when a number of CPU hogs compete for the CPUs
at the same time (thanks to Mike). This is largly because the task group's
load average tracking cross CPUs lags behind the real changes.

To fix this we accelerate the group share distribution process by using
the load.weight of the cfs_rq. This may increase the entire group's
share, but we have to do so to protect the (fragile) interactive
tasks, especially from CPU hogs.

Reported-by: Mike Galbraith 
Tested-by: Dietmar Eggemann 
Tested-by: Mike Galbraith 
Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Dietmar Eggemann 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1444699103-20272-1-git-send-email-yuyang.du@intel.com
Signed-off-by: Ingo Molnar