linux-stable.git/kernel/sched, branch v4.4.201

sched/core: Fix CPU controller for !RT_GROUP_SCHED

2019-10-05T10:27:45+00:00

[ Upstream commit a07db5c0865799ebed1f88be0df50c581fb65029 ]

On !CONFIG_RT_GROUP_SCHED configurations it is currently not possible to
move RT tasks between cgroups to which CPU controller has been attached;
but it is oddly possible to first move tasks around and then make them
RT (setschedule to FIFO/RR).

E.g.:

  # mkdir /sys/fs/cgroup/cpu,cpuacct/group1
  # chrt -fp 10 $$
  # echo $$ > /sys/fs/cgroup/cpu,cpuacct/group1/tasks
  bash: echo: write error: Invalid argument
  # chrt -op 0 $$
  # echo $$ > /sys/fs/cgroup/cpu,cpuacct/group1/tasks
  # chrt -fp 10 $$
  # cat /sys/fs/cgroup/cpu,cpuacct/group1/tasks
  2345
  2598
  # chrt -p 2345
  pid 2345's current scheduling policy: SCHED_FIFO
  pid 2345's current scheduling priority: 10

Also, as Michal noted, it is currently not possible to enable CPU
controller on unified hierarchy with !CONFIG_RT_GROUP_SCHED (if there
are any kernel RT threads in root cgroup, they can't be migrated to the
newly created CPU controller's root in cgroup_update_dfl_csses()).

Existing code comes with a comment saying the "we don't support RT-tasks
being in separate groups". Such comment is however stale and belongs to
pre-RT_GROUP_SCHED times. Also, it doesn't make much sense for
!RT_GROUP_ SCHED configurations, since checks related to RT bandwidth
are not performed at all in these cases.

Make moving RT tasks between CPU controller groups viable by removing
special case check for RT (and DEADLINE) tasks.

Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Michal Koutný 
Reviewed-by: Daniel Bristot de Oliveira 
Acked-by: Tejun Heo 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: lizefan@huawei.com
Cc: longman@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: rostedt@goodmis.org
Link: https://lkml.kernel.org/r/20190719063455.27328-1-juri.lelli@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/fair: Fix imbalance due to CPU affinity

2019-10-05T10:27:45+00:00

[ Upstream commit f6cad8df6b30a5d2bbbd2e698f74b4cafb9fb82b ]

The load_balance() has a dedicated mecanism to detect when an imbalance
is due to CPU affinity and must be handled at parent level. In this case,
the imbalance field of the parent's sched_group is set.

The description of sg_imbalanced() gives a typical example of two groups
of 4 CPUs each and 4 tasks each with a cpumask covering 1 CPU of the first
group and 3 CPUs of the second group. Something like:

	{ 0 1 2 3 } { 4 5 6 7 }
	        *     * * *

But the load_balance fails to fix this UC on my octo cores system
made of 2 clusters of quad cores.

Whereas the load_balance is able to detect that the imbalanced is due to
CPU affinity, it fails to fix it because the imbalance field is cleared
before letting parent level a chance to run. In fact, when the imbalance is
detected, the load_balance reruns without the CPU with pinned tasks. But
there is no other running tasks in the situation described above and
everything looks balanced this time so the imbalance field is immediately
cleared.

The imbalance field should not be cleared if there is no other task to move
when the imbalance is detected.

Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/1561996022-28829-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/fair: Don't free p->numa_faults with concurrent readers

2019-08-04T07:35:02+00:00

commit 16d51a590a8ce3befb1308e0e7ab77f3b661af33 upstream.

When going through execve(), zero out the NUMA fault statistics instead of
freeing them.

During execve, the task is reachable through procfs and the scheduler. A
concurrent /proc/*/sched reader can read data from a freed ->numa_faults
allocation (confirmed by KASAN) and write it back to userspace.
I believe that it would also be possible for a use-after-free read to occur
through a race between a NUMA fault and execve(): task_numa_fault() can
lead to task_numa_compare(), which invokes task_weight() on the currently
running task of a different CPU.

Another way to fix this would be to make ->numa_faults RCU-managed or add
extra locking, but it seems easier to wipe the NUMA fault statistics on
execve.

Signed-off-by: Jann Horn 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Fixes: 82727018b0d3 ("sched/numa: Call task_numa_free() from do_execve()")
Link: https://lkml.kernel.org/r/20190716152047.14424-1-jannh@google.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched/core: Handle overflow in cpu_shares_write_u64

2019-06-11T10:23:58+00:00

[ Upstream commit 5b61d50ab4ef590f5e1d4df15cd2cea5f5715308 ]

Bit shift in scale_load() could overflow shares. This patch saturates
it to MAX_SHARES like following sched_group_set_shares().

Example:

 # echo 9223372036854776832 > cpu.shares
 # cat cpu.shares

Before patch: 1024
After pattch: 262144

Signed-off-by: Konstantin Khlebnikov 
Acked-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/155125501891.293431.3345233332801109696.stgit@buzz
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/core: Check quota and period overflow at usec to nsec conversion

2019-06-11T10:23:58+00:00

[ Upstream commit 1a8b4540db732ca16c9e43ac7c08b1b8f0b252d8 ]

Large values could overflow u64 and pass following sanity checks.

 # echo 18446744073750000 > cpu.cfs_period_us
 # cat cpu.cfs_period_us
 40448

 # echo 18446744073750000 > cpu.cfs_quota_us
 # cat cpu.cfs_quota_us
 40448

After this patch they will fail with -EINVAL.

Signed-off-by: Konstantin Khlebnikov 
Acked-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/155125502079.293431.3947497929372138600.stgit@buzz
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched: Add sched_smt_active()

2019-05-16T17:45:11+00:00

Add the sched_smt_active() function needed for some x86 speculation
mitigations.  This was introduced upstream by commits 1b568f0aabf2
"sched/core: Optimize SCHED_SMT", ba2591a5993e "sched/smt: Update
sched_smt_present at runtime", c5511d03ec09 "sched/smt: Make
sched_smt_present track topology", and 321a874a7ef8 "sched/smt: Expose
sched_smt_present static key".  The upstream implementation uses the
static_key_{disable,enable}_cpuslocked() functions, which aren't
practical to backport.

Signed-off-by: Ben Hutchings 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Peter Zijlstra (Intel) 
Cc: Konrad Rzeszutek Wilk 
Signed-off-by: Greg Kroah-Hartman

sched/numa: Fix a possible divide-by-zero

2019-05-16T17:44:43+00:00

commit a860fa7b96e1a1c974556327aa1aee852d434c21 upstream.

sched_clock_cpu() may not be consistent between CPUs. If a task
migrates to another CPU, then se.exec_start is set to that CPU's
rq_clock_task() by update_stats_curr_start(). Specifically, the new
value might be before the old value due to clock skew.

So then if in numa_get_avg_runtime() the expression:

  'now - p->last_task_numa_placement'

ends up as -1, then the divider '*period + 1' in task_numa_placement()
is 0 and things go bang. Similar to update_curr(), check if time goes
backwards to avoid this.

[ peterz: Wrote new changelog. ]
[ mingo: Tweaked the code comment. ]

Signed-off-by: Xie XiuQi 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: cj.chengjian@huawei.com
Cc: 
Link: http://lkml.kernel.org/r/20190425080016.GX11158@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup

2019-04-27T07:34:02+00:00

[ Upstream commit 2e8e19226398db8265a8e675fcc0118b9e80c9e8 ]

With extremely short cfs_period_us setting on a parent task group with a large
number of children the for loop in sched_cfs_period_timer() can run until the
watchdog fires. There is no guarantee that the call to hrtimer_forward_now()
will ever return 0.  The large number of children can make
do_sched_cfs_period_timer() take longer than the period.

 NMI watchdog: Watchdog detected hard LOCKUP on cpu 24
 RIP: 0010:tg_nop+0x0/0x10
  
  walk_tg_tree_from+0x29/0xb0
  unthrottle_cfs_rq+0xe0/0x1a0
  distribute_cfs_runtime+0xd3/0xf0
  sched_cfs_period_timer+0xcb/0x160
  ? sched_cfs_slack_timer+0xd0/0xd0
  __hrtimer_run_queues+0xfb/0x270
  hrtimer_interrupt+0x122/0x270
  smp_apic_timer_interrupt+0x6a/0x140
  apic_timer_interrupt+0xf/0x20
  

To prevent this we add protection to the loop that detects when the loop has run
too many times and scales the period and quota up, proportionally, so that the timer
can complete before then next period expires.  This preserves the relative runtime
quota while preventing the hard lockup.

A warning is issued reporting this state and the new values.

Signed-off-by: Phil Auld 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: Anton Blanchard 
Cc: Ben Segall 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190319130005.25492-1-pauld@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/fair: Do not re-read ->h_load_next during hierarchical load calculation

2019-04-27T07:33:56+00:00

commit 0e9f02450da07fc7b1346c8c32c771555173e397 upstream.

A NULL pointer dereference bug was reported on a distribution kernel but
the same issue should be present on mainline kernel. It occured on s390
but should not be arch-specific.  A partial oops looks like:

  Unable to handle kernel pointer dereference in virtual kernel address space
  ...
  Call Trace:
    ...
    try_to_wake_up+0xfc/0x450
    vhost_poll_wakeup+0x3a/0x50 [vhost]
    __wake_up_common+0xbc/0x178
    __wake_up_common_lock+0x9e/0x160
    __wake_up_sync_key+0x4e/0x60
    sock_def_readable+0x5e/0x98

The bug hits any time between 1 hour to 3 days. The dereference occurs
in update_cfs_rq_h_load when accumulating h_load. The problem is that
cfq_rq->h_load_next is not protected by any locking and can be updated
by parallel calls to task_h_load. Depending on the compiler, code may be
generated that re-reads cfq_rq->h_load_next after the check for NULL and
then oops when reading se->avg.load_avg. The dissassembly showed that it
was possible to reread h_load_next after the check for NULL.

While this does not appear to be an issue for later compilers, it's still
an accident if the correct code is generated. Full locking in this path
would have high overhead so this patch uses READ_ONCE to read h_load_next
only once and check for NULL before dereferencing. It was confirmed that
there were no further oops after 10 days of testing.

As Peter pointed out, it is also necessary to use WRITE_ONCE() to avoid any
potential problems with store tearing.

Signed-off-by: Mel Gorman 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Valentin Schneider 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: 
Fixes: 685207963be9 ("sched: Move h_load calculation to task_h_load()")
Link: https://lkml.kernel.org/r/20190319123610.nsivgf3mjbjjesxb@techsingularity.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

vmstat: make vmstat_updater deferrable again and shut down on idle

2019-04-03T04:23:21+00:00

[ Upstream commit 0eb77e9880321915322d42913c3b53241739c8aa ]

Currently the vmstat updater is not deferrable as a result of commit
ba4877b9ca51 ("vmstat: do not use deferrable delayed work for
vmstat_update").  This in turn can cause multiple interruptions of the
applications because the vmstat updater may run at

Make vmstate_update deferrable again and provide a function that folds
the differentials when the processor is going to idle mode thus
addressing the issue of the above commit in a clean way.

Note that the shepherd thread will continue scanning the differentials
from another processor and will reenable the vmstat workers if it
detects any changes.

Fixes: ba4877b9ca51 ("vmstat: do not use deferrable delayed work for vmstat_update")
Signed-off-by: Christoph Lameter 
Cc: Michal Hocko 
Cc: Johannes Weiner 
Cc: Tetsuo Handa 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin