linux.git/kernel/sched/core.c, branch v5.8-rc3

smp, irq_work: Continue smp_call_function() and irq_work() integration

2020-06-28T15:01:20+00:00

Instead of relying on BUG_ON() to ensure the various data structures
line up, use a bunch of horrible unions to make it all automatic.

Much of the union magic is to ensure irq_work and smp_call_function do
not (yet) see the members of their respective data structures change
name.

Suggested-by: Linus Torvalds 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Frederic Weisbecker 
Link: https://lkml.kernel.org/r/20200622100825.844455025@infradead.org

sched/core: s/WF_ON_RQ/WQ_ON_CPU/

2020-06-28T15:01:20+00:00

Use a better name for this poorly named flag, to avoid confusion...

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Acked-by: Mel Gorman 
Link: https://lkml.kernel.org/r/20200622100825.785115830@infradead.org

sched/core: Fix ttwu() race

2020-06-28T15:01:20+00:00

Paul reported rcutorture occasionally hitting a NULL deref:

  sched_ttwu_pending()
    ttwu_do_wakeup()
      check_preempt_curr() := check_preempt_wakeup()
        find_matching_se()
          is_same_group()
            if (se->cfs_rq == pse->cfs_rq) <-- *BOOM*

Debugging showed that this only appears to happen when we take the new
code-path from commit:

  2ebb17717550 ("sched/core: Offload wakee task activation if it the wakee is descheduling")

and only when @cpu == smp_processor_id(). Something which should not
be possible, because p->on_cpu can only be true for remote tasks.
Similarly, without the new code-path from commit:

  c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")

this would've unconditionally hit:

  smp_cond_load_acquire(&p->on_cpu, !VAL);

and if: 'cpu == smp_processor_id() && p->on_cpu' is possible, this
would result in an instant live-lock (with IRQs disabled), something
that hasn't been reported.

The NULL deref can be explained however if the task_cpu(p) load at the
beginning of try_to_wake_up() returns an old value, and this old value
happens to be smp_processor_id(). Further assume that the p->on_cpu
load accurately returns 1, it really is still running, just not here.

Then, when we enqueue the task locally, we can crash in exactly the
observed manner because p->se.cfs_rq != rq->cfs_rq, because p's cfs_rq
is from the wrong CPU, therefore we'll iterate into the non-existant
parents and NULL deref.

The closest semi-plausible scenario I've managed to contrive is
somewhat elaborate (then again, actual reproduction takes many CPU
hours of rcutorture, so it can't be anything obvious):

					X->cpu = 1
					rq(1)->curr = X

	CPU0				CPU1				CPU2

					// switch away from X
					LOCK rq(1)->lock
					smp_mb__after_spinlock
					dequeue_task(X)
					  X->on_rq = 9
					switch_to(Z)
					  X->on_cpu = 0
					UNLOCK rq(1)->lock

									// migrate X to cpu 0
									LOCK rq(1)->lock
									dequeue_task(X)
									set_task_cpu(X, 0)
									  X->cpu = 0
									UNLOCK rq(1)->lock

									LOCK rq(0)->lock
									enqueue_task(X)
									  X->on_rq = 1
									UNLOCK rq(0)->lock

	// switch to X
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	switch_to(X)
	  X->on_cpu = 1
	UNLOCK rq(0)->lock

	// X goes sleep
	X->state = TASK_UNINTERRUPTIBLE
	smp_mb();			// wake X
					ttwu()
					  LOCK X->pi_lock
					  smp_mb__after_spinlock

					  if (p->state)

					  cpu = X->cpu; // =? 1

					  smp_rmb()

	// X calls schedule()
	LOCK rq(0)->lock
	smp_mb__after_spinlock
	dequeue_task(X)
	  X->on_rq = 0

					  if (p->on_rq)

					  smp_rmb();

					  if (p->on_cpu && ttwu_queue_wakelist(..)) [*]

					  smp_cond_load_acquire(&p->on_cpu, !VAL)

					  cpu = select_task_rq(X, X->wake_cpu, ...)
					  if (X->cpu != cpu)
	switch_to(Y)
	  X->on_cpu = 0
	UNLOCK rq(0)->lock

However I'm having trouble convincing myself that's actually possible
on x86_64 -- after all, every LOCK implies an smp_mb() there, so if ttwu
observes ->state != RUNNING, it must also observe ->cpu != 1.

(Most of the previous ttwu() races were found on very large PowerPC)

Nevertheless, this fully explains the observed failure case.

Fix it by ordering the task_cpu(p) load after the p->on_cpu load,
which is easy since nothing actually uses @cpu before this.

Fixes: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
Reported-by: Paul E. McKenney 
Tested-by: Paul E. McKenney 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Link: https://lkml.kernel.org/r/20200622125649.GC576871@hirez.programming.kicks-ass.net

sched/core: Fix PI boosting between RT and DEADLINE tasks

2020-06-28T15:01:20+00:00

syzbot reported the following warning:

 WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504

At deadline.c:628 we have:

 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 624 {
 625 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 626 	struct rq *rq = rq_of_dl_rq(dl_rq);
 627
 628 	WARN_ON(dl_se->dl_boosted);
 629 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
        [...]
     }

Which means that setup_new_dl_entity() has been called on a task
currently boosted. This shouldn't happen though, as setup_new_dl_entity()
is only called when the 'dynamic' deadline of the new entity
is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this
condition.

Digging through the PI code I noticed that what above might in fact happen
if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the
first branch of boosting conditions we check only if a pi_task 'dynamic'
deadline is earlier than mutex holder's and in this case we set mutex
holder to be dl_boosted. However, since RT 'dynamic' deadlines are only
initialized if such tasks get boosted at some point (or if they become
DEADLINE of course), in general RT 'dynamic' deadlines are usually equal
to 0 and this verifies the aforementioned condition.

Fix it by checking that the potential donor task is actually (even if
temporary because in turn boosted) running at DEADLINE priority before
using its 'dynamic' deadline value.

Fixes: 2d3d891d3344 ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Daniel Bristot de Oliveira 
Tested-by: Daniel Wagner 
Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain

sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption

2020-06-28T15:01:20+00:00

This function is concerned with the long-term CPU mask, not the
transitory mask the task might have while migrate disabled.  Before
this patch, if a task was migrate-disabled at the time
__set_cpus_allowed_ptr() was called, and the new mask happened to be
equal to the CPU that the task was running on, then the mask update
would be lost.

Signed-off-by: Scott Wood 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Link: https://lkml.kernel.org/r/20200617121742.cpxppyi7twxmpin7@linutronix.de

kernel: rename show_stack_loglvl() => show_stack()

2020-06-09T16:39:13+00:00

Now the last users of show_stack() got converted to use an explicit log
level, show_stack_loglvl() can drop it's redundant suffix and become once
again well known show_stack().

Signed-off-by: Dmitry Safonov 
Signed-off-by: Andrew Morton 
Link: http://lkml.kernel.org/r/20200418201944.482088-51-dima@arista.com
Signed-off-by: Linus Torvalds

sched: print stack trace with KERN_INFO

2020-06-09T16:39:12+00:00

Aligning with other messages printed in sched_show_task() - use KERN_INFO
to print the backtrace.

Signed-off-by: Dmitry Safonov 
Signed-off-by: Andrew Morton 
Cc: Ben Segall 
Cc: Dietmar Eggemann 
Cc: Ingo Molnar 
Cc: Juri Lelli 
Cc: Mel Gorman 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Vincent Guittot 
Link: http://lkml.kernel.org/r/20200418201944.482088-49-dima@arista.com
Signed-off-by: Linus Torvalds

kallsyms/printk: add loglvl to print_ip_sym()

2020-06-09T16:39:10+00:00

Patch series "Add log level to show_stack()", v3.

Add log level argument to show_stack().

Done in three stages:
1. Introducing show_stack_loglvl() for every architecture
2. Migrating old users with an explicit log level
3. Renaming show_stack_loglvl() into show_stack()

Justification:

- It's a design mistake to move a business-logic decision into platform
  realization detail.

- I have currently two patches sets that would benefit from this work:
  Removing console_loglevel jumps in sysrq driver [1] Hung task warning
  before panic [2] - suggested by Tetsuo (but he probably didn't realise
  what it would involve).

- While doing (1), (2) the backtraces were adjusted to headers and other
  messages for each situation - so there won't be a situation when the
  backtrace is printed, but the headers are missing because they have
  lesser log level (or the reverse).

- As the result in (2) plays with console_loglevel for kdb are removed.

The least important for upstream, but maybe still worth to note that every
company I've worked in so far had an off-list patch to print backtrace
with the needed log level (but only for the architecture they cared
about).  If you have other ideas how you will benefit from show_stack()
with a log level - please, reply to this cover letter.

See also discussion on v1:
https://lore.kernel.org/linux-riscv/20191106083538.z5nlpuf64cigxigh@pathway.suse.cz/

This patch (of 50):

print_ip_sym() needs to have a log level parameter to comply with other
parts being printed.  Otherwise, half of the expected backtrace would be
printed and other may be missing with some logging level.

The following callee(s) are using now the adjusted log level:
- microblaze/unwind: the same level as headers & userspace unwind.
  Note that pr_debug()'s there are for debugging the unwinder itself.
- nds32/traps: symbol addresses are printed with the same log level
  as backtrace headers.
- lockdep: ip for locking issues is printed with the same log level
  as other part of the warning.
- sched: ip where preemption was disabled is printed as error like
  the rest part of the message.
- ftrace: bug reports are now consistent in the log level being used.

Signed-off-by: Dmitry Safonov 
Signed-off-by: Andrew Morton 
Acked-by: Steven Rostedt (VMware) 
Cc: Albert Ou 
Cc: Ben Segall 
Cc: Dietmar Eggemann 
Cc: Greentime Hu 
Cc: Greg Kroah-Hartman 
Cc: Ingo Molnar 
Cc: James Hogan 
Cc: Juri Lelli 
Cc: Mel Gorman 
Cc: Michal Simek 
Cc: Palmer Dabbelt 
Cc: Paul Burton 
Cc: Paul Walmsley 
Cc: Peter Zijlstra 
Cc: Ralf Baechle 
Cc: Thomas Gleixner 
Cc: Vincent Chen 
Cc: Vincent Guittot 
Cc: Will Deacon 
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Dmitry Safonov 
Cc: Jiri Slaby 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Ivan Kokshaysky 
Cc: Matt Turner 
Cc: Richard Henderson 
Cc: Vineet Gupta 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Aurelien Jacquiot 
Cc: Mark Salter 
Cc: Guo Ren 
Cc: Yoshinori Sato 
Cc: Brian Cain 
Cc: Fenghua Yu 
Cc: Tony Luck 
Cc: Geert Uytterhoeven 
Cc: Ley Foon Tan 
Cc: Jonas Bonn 
Cc: Stafford Horne 
Cc: Stefan Kristiansson 
Cc: Helge Deller 
Cc: "James E.J. Bottomley" 
Cc: Benjamin Herrenschmidt 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Cc: Christian Borntraeger 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Rich Felker 
Cc: "David S. Miller" 
Cc: Anton Ivanov 
Cc: Jeff Dike 
Cc: Richard Weinberger 
Cc: Guan Xuetao 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: Chris Zankel 
Cc: Max Filippov 
Cc: Len Brown 
Cc: Pavel Machek 
Cc: "Rafael J. Wysocki" 
Cc: "Rafael J. Wysocki" 
Cc: Daniel Thompson 
Cc: Douglas Anderson 
Cc: Jason Wessel 
Link: http://lkml.kernel.org/r/20200418201944.482088-2-dima@arista.com
Signed-off-by: Linus Torvalds

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

2020-06-03T23:27:18+00:00

Pull networking updates from David Miller:

 1) Allow setting bluetooth L2CAP modes via socket option, from Luiz
    Augusto von Dentz.

 2) Add GSO partial support to igc, from Sasha Neftin.

 3) Several cleanups and improvements to r8169 from Heiner Kallweit.

 4) Add IF_OPER_TESTING link state and use it when ethtool triggers a
    device self-test. From Andrew Lunn.

 5) Start moving away from custom driver versions, use the globally
    defined kernel version instead, from Leon Romanovsky.

 6) Support GRO vis gro_cells in DSA layer, from Alexander Lobakin.

 7) Allow hard IRQ deferral during NAPI, from Eric Dumazet.

 8) Add sriov and vf support to hinic, from Luo bin.

 9) Support Media Redundancy Protocol (MRP) in the bridging code, from
    Horatiu Vultur.

10) Support netmap in the nft_nat code, from Pablo Neira Ayuso.

11) Allow UDPv6 encapsulation of ESP in the ipsec code, from Sabrina
    Dubroca. Also add ipv6 support for espintcp.

12) Lots of ReST conversions of the networking documentation, from Mauro
    Carvalho Chehab.

13) Support configuration of ethtool rxnfc flows in bcmgenet driver,
    from Doug Berger.

14) Allow to dump cgroup id and filter by it in inet_diag code, from
    Dmitry Yakunin.

15) Add infrastructure to export netlink attribute policies to
    userspace, from Johannes Berg.

16) Several optimizations to sch_fq scheduler, from Eric Dumazet.

17) Fallback to the default qdisc if qdisc init fails because otherwise
    a packet scheduler init failure will make a device inoperative. From
    Jesper Dangaard Brouer.

18) Several RISCV bpf jit optimizations, from Luke Nelson.

19) Correct the return type of the ->ndo_start_xmit() method in several
    drivers, it's netdev_tx_t but many drivers were using
    'int'. From Yunjian Wang.

20) Add an ethtool interface for PHY master/slave config, from Oleksij
    Rempel.

21) Add BPF iterators, from Yonghang Song.

22) Add cable test infrastructure, including ethool interfaces, from
    Andrew Lunn. Marvell PHY driver is the first to support this
    facility.

23) Remove zero-length arrays all over, from Gustavo A. R. Silva.

24) Calculate and maintain an explicit frame size in XDP, from Jesper
    Dangaard Brouer.

25) Add CAP_BPF, from Alexei Starovoitov.

26) Support terse dumps in the packet scheduler, from Vlad Buslov.

27) Support XDP_TX bulking in dpaa2 driver, from Ioana Ciornei.

28) Add devm_register_netdev(), from Bartosz Golaszewski.

29) Minimize qdisc resets, from Cong Wang.

30) Get rid of kernel_getsockopt and kernel_setsockopt in order to
    eliminate set_fs/get_fs calls. From Christoph Hellwig.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2517 commits)
  selftests: net: ip_defrag: ignore EPERM
  net_failover: fixed rollback in net_failover_open()
  Revert "tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv"
  Revert "tipc: Fix potential tipc_node refcnt leak in tipc_rcv"
  vmxnet3: allow rx flow hash ops only when rss is enabled
  hinic: add set_channels ethtool_ops support
  selftests/bpf: Add a default $(CXX) value
  tools/bpf: Don't use $(COMPILE.c)
  bpf, selftests: Use bpf_probe_read_kernel
  s390/bpf: Use bcr 0,%0 as tail call nop filler
  s390/bpf: Maintain 8-byte stack alignment
  selftests/bpf: Fix verifier test
  selftests/bpf: Fix sample_cnt shared between two threads
  bpf, selftests: Adapt cls_redirect to call csum_level helper
  bpf: Add csum_level helper for fixing up csum levels
  bpf: Fix up bpf_skb_adjust_room helper's skb csum setting
  sfc: add missing annotation for efx_ef10_try_update_nic_stats_vf()
  crypto/chtls: IPv6 support for inline TLS
  Crypto/chcr: Fixes a coccinile check error
  Crypto/chcr: Fixes compilations warnings
  ...

Merge tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-06-03T20:06:42+00:00

Pull scheduler updates from Ingo Molnar:
 "The changes in this cycle are:

   - Optimize the task wakeup CPU selection logic, to improve
     scalability and reduce wakeup latency spikes

   - PELT enhancements

   - CFS bandwidth handling fixes

   - Optimize the wakeup path by remove rq->wake_list and replacing it
     with ->ttwu_pending

   - Optimize IPI cross-calls by making flush_smp_call_function_queue()
     process sync callbacks first.

   - Misc fixes and enhancements"

* tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  irq_work: Define irq_work_single() on !CONFIG_IRQ_WORK too
  sched/headers: Split out open-coded prototypes into kernel/sched/smp.h
  sched: Replace rq::wake_list
  sched: Add rq::ttwu_pending
  irq_work, smp: Allow irq_work on call_single_queue
  smp: Optimize send_call_function_single_ipi()
  smp: Move irq_work_run() out of flush_smp_call_function_queue()
  smp: Optimize flush_smp_call_function_queue()
  sched: Fix smp_call_function_single_async() usage for ILB
  sched/core: Offload wakee task activation if it the wakee is descheduling
  sched/core: Optimize ttwu() spinning on p->on_cpu
  sched: Defend cfs and rt bandwidth quota against overflow
  sched/cpuacct: Fix charge cpuacct.usage_sys
  sched/fair: Replace zero-length array with flexible-array
  sched/pelt: Sync util/runnable_sum with PELT window when propagating
  sched/cpuacct: Use __this_cpu_add() instead of this_cpu_ptr()
  sched/fair: Optimize enqueue_task_fair()
  sched: Make scheduler_ipi inline
  sched: Clean up scheduler_ipi()
  sched/core: Simplify sched_init()
  ...

linux.git/kernel/sched/core.c, branch v5.8-rc3

smp, irq_work: Continue smp_call_function*() and irq_work*() integration

sched/core: s/WF_ON_RQ/WQ_ON_CPU/

sched/core: Fix ttwu() race

sched/core: Fix PI boosting between RT and DEADLINE tasks

sched/core: Check cpus_mask, not cpus_ptr in __set_cpus_allowed_ptr(), to fix mask corruption

kernel: rename show_stack_loglvl() => show_stack()

sched: print stack trace with KERN_INFO

kallsyms/printk: add loglvl to print_ip_sym()

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next

Merge tag 'sched-core-2020-06-02' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

smp, irq_work: Continue smp_call_function() and irq_work() integration