linux-stable.git/kernel/sched, branch v4.14.69

sched/rt: Restore rt_runtime after disabling RT_RUNTIME_SHARE

2018-09-05T07:26:29+00:00

[ Upstream commit f3d133ee0a17d5694c6f21873eec9863e11fa423 ]

NO_RT_RUNTIME_SHARE feature is used to prevent a CPU borrow enough
runtime with a spin-rt-task.

However, if RT_RUNTIME_SHARE feature is enabled and rt_rq has borrowd
enough rt_runtime at the beginning, rt_runtime can't be restored to
its initial bandwidth rt_runtime after we disable RT_RUNTIME_SHARE.

E.g. on my PC with 4 cores, procedure to reproduce:
1) Make sure  RT_RUNTIME_SHARE is enabled
 cat /sys/kernel/debug/sched_features
  GENTLE_FAIR_SLEEPERS START_DEBIT NO_NEXT_BUDDY LAST_BUDDY
  CACHE_HOT_BUDDY WAKEUP_PREEMPTION NO_HRTICK NO_DOUBLE_TICK
  LB_BIAS NONTASK_CAPACITY TTWU_QUEUE NO_SIS_AVG_CPU SIS_PROP
  NO_WARN_DOUBLE_CLOCK RT_PUSH_IPI RT_RUNTIME_SHARE NO_LB_MIN
  ATTACH_AGE_LOAD WA_IDLE WA_WEIGHT WA_BIAS
2) Start a spin-rt-task
 ./loop_rr &
3) set affinity to the last cpu
 taskset -p 8 $pid_of_loop_rr
4) Observe that last cpu have borrowed enough runtime.
 cat /proc/sched_debug | grep rt_runtime
  .rt_runtime                    : 950.000000
  .rt_runtime                    : 900.000000
  .rt_runtime                    : 950.000000
  .rt_runtime                    : 1000.000000
5) Disable RT_RUNTIME_SHARE
 echo NO_RT_RUNTIME_SHARE > /sys/kernel/debug/sched_features
6) Observe that rt_runtime can not been restored
 cat /proc/sched_debug | grep rt_runtime
  .rt_runtime                    : 950.000000
  .rt_runtime                    : 900.000000
  .rt_runtime                    : 950.000000
  .rt_runtime                    : 1000.000000

This patch help to restore rt_runtime after we disable
RT_RUNTIME_SHARE.

Signed-off-by: Hailong Liu 
Signed-off-by: Jiang Biao 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: zhong.weidong@zte.com.cn
Link: http://lkml.kernel.org/r/1531874815-39357-1-git-send-email-liu.hailong6@zte.com.cn
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/smt: Update sched_smt_present at runtime

2018-08-15T16:12:51+00:00

commit ba2591a5993eabcc8e874e30f361d8ffbb10d6d4 upstream

The static key sched_smt_present is only updated at boot time when SMT
siblings have been detected. Booting with maxcpus=1 and bringing the
siblings online after boot rebuilds the scheduling domains correctly but
does not update the static key, so the SMT code is not enabled.

Let the key be updated in the scheduler CPU hotplug code to fix this.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Konrad Rzeszutek Wilk 
Acked-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

sched/core: Require cpu_active() in select_task_rq(), for user tasks

2018-07-08T13:30:53+00:00

[ Upstream commit 7af443ee1697607541c6346c87385adab2214743 ]

select_task_rq() is used in a few paths to select the CPU upon which a
thread should be run - for example it is used by try_to_wake_up() & by
fork or exec balancing. As-is it allows use of any online CPU that is
present in the task's cpus_allowed mask.

This presents a problem because there is a period whilst CPUs are
brought online where a CPU is marked online, but is not yet fully
initialized - ie. the period where CPUHP_AP_ONLINE_IDLE <= state <
CPUHP_ONLINE. Usually we don't run any user tasks during this window,
but there are corner cases where this can happen. An example observed
is:

  - Some user task A, running on CPU X, forks to create task B.

  - sched_fork() calls __set_task_cpu() with cpu=X, setting task B's
    task_struct::cpu field to X.

  - CPU X is offlined.

  - Task A, currently somewhere between the __set_task_cpu() in
    copy_process() and the call to wake_up_new_task(), is migrated to
    CPU Y by migrate_tasks() when CPU X is offlined.

  - CPU X is onlined, but still in the CPUHP_AP_ONLINE_IDLE state. The
    scheduler is now active on CPU X, but there are no user tasks on
    the runqueue.

  - Task A runs on CPU Y & reaches wake_up_new_task(). This calls
    select_task_rq() with cpu=X, taken from task B's task_struct,
    and select_task_rq() allows CPU X to be returned.

  - Task A enqueues task B on CPU X's runqueue, via activate_task() &
    enqueue_task().

  - CPU X now has a user task on its runqueue before it has reached the
    CPUHP_ONLINE state.

In most cases, the user tasks that schedule on the newly onlined CPU
have no idea that anything went wrong, but one case observed to be
problematic is if the task goes on to invoke the sched_setaffinity
syscall. The newly onlined CPU reaches the CPUHP_AP_ONLINE_IDLE state
before the CPU that brought it online calls stop_machine_unpark(). This
means that for a portion of the window of time between
CPUHP_AP_ONLINE_IDLE & CPUHP_ONLINE the newly onlined CPU's struct
cpu_stopper has its enabled field set to false. If a user thread is
executed on the CPU during this window and it invokes sched_setaffinity
with a CPU mask that does not include the CPU it's running on, then when
__set_cpus_allowed_ptr() calls stop_one_cpu() intending to invoke
migration_cpu_stop() and perform the actual migration away from the CPU
it will simply return -ENOENT rather than calling migration_cpu_stop().
We then return from the sched_setaffinity syscall back to the user task
that is now running on a CPU which it just asked not to run on, and
which is not present in its cpus_allowed mask.

This patch resolves the problem by having select_task_rq() enforce that
user tasks run on CPUs that are active - the same requirement that
select_fallback_rq() already enforces. This should ensure that newly
onlined CPUs reach the CPUHP_AP_ACTIVE state before being able to
schedule user tasks, and also implies that bringup_wait_for_ap() will
have called stop_machine_unpark() which resolves the sched_setaffinity
issue above.

I haven't yet investigated them, but it may be of interest to review
whether any of the actions performed by hotplug states between
CPUHP_AP_ONLINE_IDLE & CPUHP_AP_ACTIVE could have similar unintended
effects on user tasks that might schedule before they are reached, which
might widen the scope of the problem from just affecting the behaviour
of sched_setaffinity.

Signed-off-by: Paul Burton 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20180526154648.11635-2-paul.burton@mips.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/core: Fix rules for running on online && !active CPUs

2018-07-08T13:30:53+00:00

[ Upstream commit 175f0e25abeaa2218d431141ce19cf1de70fa82d ]

As already enforced by the WARN() in __set_cpus_allowed_ptr(), the rules
for running on an online && !active CPU are stricter than just being a
kthread, you need to be a per-cpu kthread.

If you're not strictly per-CPU, you have better CPUs to run on and
don't need the partially booted one to get your work done.

The exception is to allow smpboot threads to bootstrap the CPU itself
and get kernel 'services' initialized before we allow userspace on it.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Tejun Heo 
Cc: Thomas Gleixner 
Fixes: 955dbdf4ce87 ("sched: Allow migrating kthreads into online but inactive CPUs")
Link: http://lkml.kernel.org/r/20170725165821.cejhb7v2s3kecems@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Make the grub_reclaim() function static

2018-06-20T19:03:01+00:00

[ Upstream commit 3febfc8a219a036633b57a34c6678e21b6a0580d ]

Since the grub_reclaim() function can be made static, make it so.

Silences the following GCC warning (W=1):

  kernel/sched/deadline.c:1120:5: warning: no previous prototype for ‘grub_reclaim’ [-Wmissing-prototypes]

Signed-off-by: Mathieu Malaterre 
Acked-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20180516200902.959-1-malat@debian.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/debug: Move the print_rt_rq() and print_dl_rq() declarations to kernel/sched/sched.h

2018-06-20T19:03:01+00:00

[ Upstream commit f6a3463063f42d9fb2c78f386437a822e0ad1792 ]

In the following commit:

  6b55c9654fcc ("sched/debug: Move print_cfs_rq() declaration to kernel/sched/sched.h")

the print_cfs_rq() prototype was added to ,
right next to the prototypes for print_cfs_stats(), print_rt_stats()
and print_dl_stats().

Finish this previous commit and also move related prototypes for
print_rt_rq() and print_dl_rq().

Remove existing extern declarations now that they not needed anymore.

Silences the following GCC warning, triggered by W=1:

  kernel/sched/debug.c:573:6: warning: no previous prototype for ‘print_rt_rq’ [-Wmissing-prototypes]
  kernel/sched/debug.c:603:6: warning: no previous prototype for ‘print_dl_rq’ [-Wmissing-prototypes]

Signed-off-by: Mathieu Malaterre 
Acked-by: Peter Zijlstra 
Cc: Linus Torvalds 
Cc: Srikar Dronamraju 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/20180516195348.30426-1-malat@debian.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/core: Introduce set_special_state()

2018-06-20T19:02:54+00:00

[ Upstream commit b5bf9a90bbebffba888c9144c5a8a10317b04064 ]

Gaurav reported a perceived problem with TASK_PARKED, which turned out
to be a broken wait-loop pattern in __kthread_parkme(), but the
reported issue can (and does) in fact happen for states that do not do
condition based sleeps.

When the 'current->state = TASK_RUNNING' store of a previous
(concurrent) try_to_wake_up() collides with the setting of a 'special'
sleep state, we can loose the sleep state.

Normal condition based wait-loops are immune to this problem, but for
sleep states that are not condition based are subject to this problem.

There already is a fix for TASK_DEAD. Abstract that and also apply it
to TASK_STOPPED and TASK_TRACED, both of which are also without
condition based wait-loop.

Reported-by: Gaurav Kohli 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Oleg Nesterov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/rt: Fix rq->clock_update_flags < RQCF_ACT_SKIP warning

2018-05-30T05:52:25+00:00

[ Upstream commit d29a20645d5e929aa7e8616f28e5d8e1c49263ec ]

While running rt-tests' pi_stress program I got the following splat:

  rq->clock_update_flags < RQCF_ACT_SKIP
  WARNING: CPU: 27 PID: 0 at kernel/sched/sched.h:960 assert_clock_updated.isra.38.part.39+0x13/0x20

  [...]

  
  enqueue_top_rt_rq+0xf4/0x150
  ? cpufreq_dbs_governor_start+0x170/0x170
  sched_rt_rq_enqueue+0x65/0x80
  sched_rt_period_timer+0x156/0x360
  ? sched_rt_rq_enqueue+0x80/0x80
  __hrtimer_run_queues+0xfa/0x260
  hrtimer_interrupt+0xcb/0x220
  smp_apic_timer_interrupt+0x62/0x120
  apic_timer_interrupt+0xf/0x20
  

  [...]

  do_idle+0x183/0x1e0
  cpu_startup_entry+0x5f/0x70
  start_secondary+0x192/0x1d0
  secondary_startup_64+0xa5/0xb0

We can get rid of it be the "traditional" means of adding an
update_rq_clock() call after acquiring the rq->lock in
do_sched_rt_period_timer().

The case for the RT task throttling (which this workload also hits)
can be ignored in that the skip_update call is actually bogus and
quite the contrary (the request bits are removed/reverted).

By setting RQCF_UPDATED we really don't care if the skip is happening
or not and will therefore make the assert_clock_updated() check happy.

Signed-off-by: Davidlohr Bueso 
Reviewed-by: Matt Fleming 
Acked-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Thomas Gleixner 
Cc: dave@stgolabs.net
Cc: linux-kernel@vger.kernel.org
Cc: rostedt@goodmis.org
Link: http://lkml.kernel.org/r/20180402164954.16255-1-dave@stgolabs.net
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

sched/autogroup: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]

2018-05-16T08:10:30+00:00

commit 354d7793070611b4df5a79fbb0f12752d0ed0cc5 upstream.

> kernel/sched/autogroup.c:230 proc_sched_autogroup_set_nice() warn: potential spectre issue 'sched_prio_to_weight'

Userspace controls @nice, sanitize the array index.

Reported-by: Dan Carpenter 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: 
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

cpufreq: schedutil: Avoid using invalid next_freq

2018-05-16T08:10:29+00:00

commit 97739501f207efe33145b918817f305b822987f8 upstream.

If the next_freq field of struct sugov_policy is set to UINT_MAX,
it shouldn't be used for updating the CPU frequency (this is a
special "invalid" value), but after commit b7eaf1aab9f8 (cpufreq:
schedutil: Avoid reducing frequency of busy CPUs prematurely) it
may be passed as the new frequency to sugov_update_commit() in
sugov_update_single().

Fix that by adding an extra check for the special UINT_MAX value
of next_freq to sugov_update_single().

Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely)
Reported-by: Viresh Kumar 
Cc: 4.12+  # 4.12+
Signed-off-by: Rafael J. Wysocki 
Acked-by: Viresh Kumar 
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Greg Kroah-Hartman