linux-stable.git/kernel/sched/core.c, branch v4.19.71

sched/core: Add __sched tag for io_schedule()

2019-07-26T07:14:08+00:00

[ Upstream commit e3b929b0a184edb35531153c5afcaebb09014f9d ]

Non-inline io_schedule() was introduced in:

  commit 10ab56434f2f ("sched/core: Separate out io_schedule_prepare() and io_schedule_finish()")

Keep in line with io_schedule_timeout(), otherwise "/proc//wchan" will
report io_schedule() rather than its callers when waiting for IO.

Reported-by: Jilong Kou 
Signed-off-by: Gao Xiang 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Tejun Heo 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Miao Xie 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: 10ab56434f2f ("sched/core: Separate out io_schedule_prepare() and io_schedule_finish()")
Link: https://lkml.kernel.org/r/20190603091338.2695-1-gaoxiang25@huawei.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

jump_label: move 'asm goto' support test to Kconfig

2019-06-04T06:02:34+00:00

commit e9666d10a5677a494260d60d1fa0b73cc7646eb3 upstream.

Currently, CONFIG_JUMP_LABEL just means "I _want_ to use jump label".

The jump label is controlled by HAVE_JUMP_LABEL, which is defined
like this:

  #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
  # define HAVE_JUMP_LABEL
  #endif

We can improve this by testing 'asm goto' support in Kconfig, then
make JUMP_LABEL depend on CC_HAS_ASM_GOTO.

Ugly #ifdef HAVE_JUMP_LABEL will go away, and CONFIG_JUMP_LABEL will
match to the real kernel capability.

Signed-off-by: Masahiro Yamada 
Acked-by: Michael Ellerman  (powerpc)
Tested-by: Sedat Dilek 
[nc: Fix trivial conflicts in 4.19
     arch/xtensa/kernel/jump_label.c doesn't exist yet
     Ensured CC_HAVE_ASM_GOTO and HAVE_JUMP_LABEL were sufficiently
     eliminated]
Signed-off-by: Nathan Chancellor 
Signed-off-by: Greg Kroah-Hartman

sched/core: Handle overflow in cpu_shares_write_u64

2019-05-31T13:46:19+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

2019-05-31T13:46:19+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/core: Fix buffer overflow in cgroup2 property cpu.max

2019-04-20T07:15:57+00:00

[ Upstream commit 4c47acd824aaaa8fc6dc519fb4e08d1522105b7a ]

Add limit into sscanf format string for on-stack buffer.

Signed-off-by: Konstantin Khlebnikov 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Tejun Heo 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Johannes Weiner 
Cc: Li Zefan 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Fixes: 0d5936344f30 ("sched: Implement interface for cgroup unified hierarchy")
Link: https://lkml.kernel.org/r/155189230232.2620.13120481613524200065.stgit@buzz
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/core: Use READ_ONCE()/WRITE_ONCE() in move_queued_task()/task_rq_lock()

2019-04-05T20:33:12+00:00

[ Upstream commit c546951d9c9300065bad253ecdf1ac59ce9d06c8 ]

move_queued_task() synchronizes with task_rq_lock() as follows:

	move_queued_task()		task_rq_lock()

	[S] ->on_rq = MIGRATING		[L] rq = task_rq()
	WMB (__set_task_cpu())		ACQUIRE (rq->lock);
	[S] ->cpu = new_cpu		[L] ->on_rq

where "[L] rq = task_rq()" is ordered before "ACQUIRE (rq->lock)" by an
address dependency and, in turn, "ACQUIRE (rq->lock)" is ordered before
"[L] ->on_rq" by the ACQUIRE itself.

Use READ_ONCE() to load ->cpu in task_rq() (c.f., task_cpu()) to honor
this address dependency.  Also, mark the accesses to ->cpu and ->on_rq
with READ_ONCE()/WRITE_ONCE() to comply with the LKMM.

Signed-off-by: Andrea Parri 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Alan Stern 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: https://lkml.kernel.org/r/20190121155240.27173-1-andrea.parri@amarulasolutions.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/wake_q: Fix wakeup ordering for wake_q

2019-03-05T16:58:49+00:00

[ Upstream commit 4c4e3731564c8945ac5ac90fc2a1e1f21cb79c92 ]

Notable cmpxchg() does not provide ordering when it fails, however
wake_q_add() requires ordering in this specific case too. Without this
it would be possible for the concurrent wakeup to not observe our
prior state.

Andrea Parri provided:

  C wake_up_q-wake_q_add

  {
	int next = 0;
	int y = 0;
  }

  P0(int *next, int *y)
  {
	int r0;

	/* in wake_up_q() */

	WRITE_ONCE(*next, 1);   /* node->next = NULL */
	smp_mb();               /* implied by wake_up_process() */
	r0 = READ_ONCE(*y);
  }

  P1(int *next, int *y)
  {
	int r1;

	/* in wake_q_add() */

	WRITE_ONCE(*y, 1);      /* wake_cond = true */
	smp_mb__before_atomic();
	r1 = cmpxchg_relaxed(next, 1, 2);
  }

  exists (0:r0=0 /\ 1:r1=0)

  This "exists" clause cannot be satisfied according to the LKMM:

  Test wake_up_q-wake_q_add Allowed
  States 3
  0:r0=0; 1:r1=1;
  0:r0=1; 1:r1=0;
  0:r0=1; 1:r1=1;
  No
  Witnesses
  Positive: 0 Negative: 3
  Condition exists (0:r0=0 /\ 1:r1=0)
  Observation wake_up_q-wake_q_add Never 0 3

Reported-by: Yongji Xie 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Davidlohr Bueso 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: Will Deacon 
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/pelt: Fix warning and clean up IRQ PELT config

2018-12-19T18:19:49+00:00

Commit 11d4afd4ff667f9b6178ee8c142c36cb78bd84db upstream.

Create a config for enabling irq load tracking in the scheduler.
irq load tracking is useful only when irq or paravirtual time is
accounted but it's only possible with SMP for now.

Also use __maybe_unused to remove the compilation warning in
update_rq_clock_task() that has been introduced by:

  2e62c4743adc ("sched/fair: Remove #ifdefs from scale_rt_capacity()")

Suggested-by: Ingo Molnar 
Reported-by: Dou Liyang 
Reported-by: Miguel Ojeda 
Signed-off-by: Vincent Guittot 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bp@alien8.de
Cc: dou_liyang@163.com
Fixes: 2e62c4743adc ("sched/fair: Remove #ifdefs from scale_rt_capacity()")
Link: http://lkml.kernel.org/r/1537867062-27285-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

sched/smt: Make sched_smt_present track topology

2018-12-05T18:32:02+00:00

commit c5511d03ec090980732e929c318a7a6374b5550e upstream

Currently the 'sched_smt_present' static key is enabled when at CPU bringup
SMT topology is observed, but it is never disabled. However there is demand
to also disable the key when the topology changes such that there is no SMT
present anymore.

Implement this by making the key count the number of cores that have SMT
enabled.

In particular, the SMT topology bits are set before interrrupts are enabled
and similarly, are cleared after interrupts are disabled for the last time
and the CPU dies.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Tim Chen 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185004.246110444@linutronix.de
Signed-off-by: Greg Kroah-Hartman

sched/core: Take the hotplug lock in sched_init_smp()

2018-11-27T15:13:06+00:00

[ Upstream commit 40fa3780bac2b654edf23f6b13f4e2dd550aea10 ]

When running on linux-next (8c60c36d0b8c ("Add linux-next specific files
for 20181019")) + CONFIG_PROVE_LOCKING=y on a big.LITTLE system (e.g.
Juno or HiKey960), we get the following report:

 [    0.748225] Call trace:
 [    0.750685]  lockdep_assert_cpus_held+0x30/0x40
 [    0.755236]  static_key_enable_cpuslocked+0x20/0xc8
 [    0.760137]  build_sched_domains+0x1034/0x1108
 [    0.764601]  sched_init_domains+0x68/0x90
 [    0.768628]  sched_init_smp+0x30/0x80
 [    0.772309]  kernel_init_freeable+0x278/0x51c
 [    0.776685]  kernel_init+0x10/0x108
 [    0.780190]  ret_from_fork+0x10/0x18

The static_key in question is 'sched_asym_cpucapacity' introduced by
commit:

  df054e8445a4 ("sched/topology: Add static_key for asymmetric CPU capacity optimizations")

In this particular case, we enable it because smp_prepare_cpus() will
end up fetching the capacity-dmips-mhz entry from the devicetree,
so we already have some asymmetry detected when entering sched_init_smp().

This didn't get detected in tip/sched/core because we were missing:

  commit cb538267ea1e ("jump_label/lockdep: Assert we hold the hotplug lock for _cpuslocked() operations")

Calls to build_sched_domains() post sched_init_smp() will hold the
hotplug lock, it just so happens that this very first call is a
special case. As stated by a comment in sched_init_smp(), "There's no
userspace yet to cause hotplug operations" so this is a harmless
warning.

However, to both respect the semantics of underlying
callees and make lockdep happy, take the hotplug lock in
sched_init_smp(). This also satisfies the comment atop
sched_init_domains() that says "Callers must hold the hotplug lock".

Reported-by: Sudeep Holla 
Tested-by: Sudeep Holla 
Signed-off-by: Valentin Schneider 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Dietmar.Eggemann@arm.com
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: morten.rasmussen@arm.com
Cc: quentin.perret@arm.com
Link: http://lkml.kernel.org/r/1540301851-3048-1-git-send-email-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin