linux-stable.git/include/linux/sched.h, branch v5.17.7

oom_kill.c: futex: delay the OOM reaper to allow time for proper futex cleanup

2022-04-27T12:41:11+00:00

commit e4a38402c36e42df28eb1a5394be87e6571fb48a upstream.

The pthread struct is allocated on PRIVATE|ANONYMOUS memory [1] which
can be targeted by the oom reaper.  This mapping is used to store the
futex robust list head; the kernel does not keep a copy of the robust
list and instead references a userspace address to maintain the
robustness during a process death.

A race can occur between exit_mm and the oom reaper that allows the oom
reaper to free the memory of the futex robust list before the exit path
has handled the futex death:

    CPU1                               CPU2
    --------------------------------------------------------------------
    page_fault
    do_exit "signal"
    wake_oom_reaper
                                        oom_reaper
                                        oom_reap_task_mm (invalidates mm)
    exit_mm
    exit_mm_release
    futex_exit_release
    futex_cleanup
    exit_robust_list
    get_user (EFAULT- can't access memory)

If the get_user EFAULT's, the kernel will be unable to recover the
waiters on the robust_list, leaving userspace mutexes hung indefinitely.

Delay the OOM reaper, allowing more time for the exit path to perform
the futex cleanup.

Reproducer: https://gitlab.com/jsavitz/oom_futex_reproducer

Based on a patch by Michal Hocko.

Link: https://elixir.bootlin.com/glibc/glibc-2.35/source/nptl/allocatestack.c#L370 [1]
Link: https://lkml.kernel.org/r/20220414144042.677008-1-npache@redhat.com
Fixes: 212925802454 ("mm: oom: let oom_reap_task and exit_mmap run concurrently")
Signed-off-by: Joel Savitz 
Signed-off-by: Nico Pache 
Co-developed-by: Joel Savitz 
Suggested-by: Thomas Gleixner 
Acked-by: Thomas Gleixner 
Acked-by: Michal Hocko 
Cc: Rafael Aquini 
Cc: Waiman Long 
Cc: Herton R. Krzesinski 
Cc: Juri Lelli 
Cc: Vincent Guittot 
Cc: Dietmar Eggemann 
Cc: Steven Rostedt 
Cc: Ben Segall 
Cc: Mel Gorman 
Cc: Daniel Bristot de Oliveira 
Cc: David Rientjes 
Cc: Andrea Arcangeli 
Cc: Davidlohr Bueso 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Joel Savitz 
Cc: Darren Hart 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched/tracing: Report TASK_RTLOCK_WAIT tasks as TASK_UNINTERRUPTIBLE

2022-04-08T11:58:39+00:00

[ Upstream commit 25795ef6299f07ce3838f3253a9cb34f64efcfae ]

TASK_RTLOCK_WAIT currently isn't part of TASK_REPORT, thus a task blocking
on an rtlock will appear as having a task state == 0, IOW TASK_RUNNING.

The actual state is saved in p->saved_state, but reading it after reading
p->__state has a few issues:
o that could still be TASK_RUNNING in the case of e.g. rt_spin_lock
o ttwu_state_match() might have changed that to TASK_RUNNING

As pointed out by Eric, adding TASK_RTLOCK_WAIT to TASK_REPORT implies
exposing a new state to userspace tools which way not know what to do with
them. The only information that needs to be conveyed here is that a task is
waiting on an rt_mutex, which matches TASK_UNINTERRUPTIBLE - there's no
need for a new state.

Reported-by: Uwe Kleine-König 
Signed-off-by: Valentin Schneider 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Steven Rostedt (Google) 
Link: https://lore.kernel.org/r/20220120162520.570782-3-valentin.schneider@arm.com
Signed-off-by: Sasha Levin

Revert "module, async: async_synchronize_full() on module init iff async is used"

2022-02-03T19:20:34+00:00

This reverts commit 774a1221e862b343388347bac9b318767336b20b.

We need to finish all async code before the module init sequence is
done.  In the reverted commit the PF_USED_ASYNC flag was added to mark a
thread that called async_schedule().  Then the PF_USED_ASYNC flag was
used to determine whether or not async_synchronize_full() needs to be
invoked.  This works when modprobe thread is calling async_schedule(),
but it does not work if module dispatches init code to a worker thread
which then calls async_schedule().

For example, PCI driver probing is invoked from a worker thread based on
a node where device is attached:

	if (cpu < nr_cpu_ids)
		error = work_on_cpu(cpu, local_pci_probe, &ddi);
	else
		error = local_pci_probe(&ddi);

We end up in a situation where a worker thread gets the PF_USED_ASYNC
flag set instead of the modprobe thread.  As a result,
async_synchronize_full() is not invoked and modprobe completes without
waiting for the async code to finish.

The issue was discovered while loading the pm80xx driver:
(scsi_mod.scan=async)

modprobe pm80xx                      worker
...
  do_init_module()
  ...
    pci_call_probe()
      work_on_cpu(local_pci_probe)
                                     local_pci_probe()
                                       pm8001_pci_probe()
                                         scsi_scan_host()
                                           async_schedule()
                                           worker->flags |= PF_USED_ASYNC;
                                     ...
      < return from worker >
  ...
  if (current->flags & PF_USED_ASYNC) <--- false
  	async_synchronize_full();

Commit 21c3c5d28007 ("block: don't request module during elevator init")
fixed the deadlock issue which the reverted commit 774a1221e862
("module, async: async_synchronize_full() on module init iff async is
used") tried to fix.

Since commit 0fdff3ec6d87 ("async, kmod: warn on synchronous
request_module() from async workers") synchronous module loading from
async is not allowed.

Given that the original deadlock issue is fixed and it is no longer
allowed to call synchronous request_module() from async we can remove
PF_USED_ASYNC flag to make module init consistently invoke
async_synchronize_full() unless async module probe is requested.

Signed-off-by: Igor Pylypiv 
Reviewed-by: Changyuan Lyu 
Reviewed-by: Luis Chamberlain 
Acked-by: Tejun Heo 
Signed-off-by: Linus Torvalds

Merge tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-23T15:35:27+00:00

Pull scheduler fixes from Borislav Petkov:
 "A bunch of fixes: forced idle time accounting, utilization values
  propagation in the sched hierarchies and other minor cleanups and
  improvements"

* tag 'sched_urgent_for_v5.17_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kernel/sched: Remove dl_boosted flag comment
  sched: Avoid double preemption in __cond_resched_*lock*()
  sched/fair: Fix all kernel-doc warnings
  sched/core: Accounting forceidle time for all tasks except idle task
  sched/pelt: Relax the sync of load_sum with load_avg
  sched/pelt: Relax the sync of runnable_sum with runnable_avg
  sched/pelt: Continue to relax the sync of util_sum with util_avg
  sched/pelt: Relax the sync of util_sum with util_avg
  psi: Fix uaf issue when psi trigger is destroyed while being polled

Merge branch 'akpm' (patches from Andrew)

2022-01-20T08:41:01+00:00

Merge more updates from Andrew Morton:
 "55 patches.

  Subsystems affected by this patch series: percpu, procfs, sysctl,
  misc, core-kernel, get_maintainer, lib, checkpatch, binfmt, nilfs2,
  hfs, fat, adfs, panic, delayacct, kconfig, kcov, and ubsan"

* emailed patches from Andrew Morton : (55 commits)
  lib: remove redundant assignment to variable ret
  ubsan: remove CONFIG_UBSAN_OBJECT_SIZE
  kcov: fix generic Kconfig dependencies if ARCH_WANTS_NO_INSTR
  lib/Kconfig.debug: make TEST_KMOD depend on PAGE_SIZE_LESS_THAN_256KB
  btrfs: use generic Kconfig option for 256kB page size limit
  arch/Kconfig: split PAGE_SIZE_LESS_THAN_256KB from PAGE_SIZE_LESS_THAN_64KB
  configs: introduce debug.config for CI-like setup
  delayacct: track delays from memory compact
  Documentation/accounting/delay-accounting.rst: add thrashing page cache and direct compact
  delayacct: cleanup flags in struct task_delay_info and functions use it
  delayacct: fix incomplete disable operation when switch enable to disable
  delayacct: support swapin delay accounting for swapping without blkio
  panic: remove oops_id
  panic: use error_report_end tracepoint on warnings
  fs/adfs: remove unneeded variable make code cleaner
  FAT: use io_schedule_timeout() instead of congestion_wait()
  hfsplus: use struct_group_attr() for memcpy() region
  nilfs2: remove redundant pointer sbufs
  fs/binfmt_elf: use PT_LOAD p_align values for static PIE
  const_structs.checkpatch: add frequently used ops structs
  ...

tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN

2022-01-20T06:52:53+00:00

As the sched:sched_switch tracepoint args are derived from the kernel,
we'd better make it same with the kernel.  So the macro TASK_COMM_LEN is
converted to type enum, then all the BPF programs can get it through
BTF.

The BPF program which wants to use TASK_COMM_LEN should include the
header vmlinux.h.  Regarding the test_stacktrace_map and
test_tracepoint, as the type defined in linux/bpf.h are also defined in
vmlinux.h, so we don't need to include linux/bpf.h again.

Link: https://lkml.kernel.org/r/20211120112738.45980-8-laoar.shao@gmail.com
Signed-off-by: Yafang Shao 
Acked-by: Andrii Nakryiko 
Acked-by: David Hildenbrand 
Cc: Mathieu Desnoyers 
Cc: Arnaldo Carvalho de Melo 
Cc: Andrii Nakryiko 
Cc: Michal Miroslaw 
Cc: Peter Zijlstra 
Cc: Steven Rostedt 
Cc: Matthew Wilcox 
Cc: David Hildenbrand 
Cc: Al Viro 
Cc: Kees Cook 
Cc: Petr Mladek 
Cc: Alexei Starovoitov 
Cc: Dennis Dalessandro 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kernel/sched: Remove dl_boosted flag comment

2022-01-18T11:10:00+00:00

since commit 2279f540ea7d ("sched/deadline: Fix priority
inheritance with multiple scheduling classes"), we should not
keep it here.

Signed-off-by: Hui Su 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Bristot de Oliveira 
Link: https://lore.kernel.org/r/20220107095254.GA49258@localhost.localdomain

Merge branch 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-01-17T03:49:30+00:00

Pull signal/exit/ptrace updates from Eric Biederman:
 "This set of changes deletes some dead code, makes a lot of cleanups
  which hopefully make the code easier to follow, and fixes bugs found
  along the way.

  The end-game which I have not yet reached yet is for fatal signals
  that generate coredumps to be short-circuit deliverable from
  complete_signal, for force_siginfo_to_task not to require changing
  userspace configured signal delivery state, and for the ptrace stops
  to always happen in locations where we can guarantee on all
  architectures that the all of the registers are saved and available on
  the stack.

  Removal of profile_task_ext, profile_munmap, and profile_handoff_task
  are the big successes for dead code removal this round.

  A bunch of small bug fixes are included, as most of the issues
  reported were small enough that they would not affect bisection so I
  simply added the fixes and did not fold the fixes into the changes
  they were fixing.

  There was a bug that broke coredumps piped to systemd-coredump. I
  dropped the change that caused that bug and replaced it entirely with
  something much more restrained. Unfortunately that required some
  rebasing.

  Some successes after this set of changes: There are few enough calls
  to do_exit to audit in a reasonable amount of time. The lifetime of
  struct kthread now matches the lifetime of struct task, and the
  pointer to struct kthread is no longer stored in set_child_tid. The
  flag SIGNAL_GROUP_COREDUMP is removed. The field group_exit_task is
  removed. Issues where task->exit_code was examined with
  signal->group_exit_code should been examined were fixed.

  There are several loosely related changes included because I am
  cleaning up and if I don't include them they will probably get lost.

  The original postings of these changes can be found at:
     https://lkml.kernel.org/r/87a6ha4zsd.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87bl1kunjj.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87r19opkx1.fsf_-_@email.froward.int.ebiederm.org

  I trimmed back the last set of changes to only the obviously correct
  once. Simply because there was less time for review than I had hoped"

* 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (44 commits)
  ptrace/m68k: Stop open coding ptrace_report_syscall
  ptrace: Remove unused regs argument from ptrace_report_syscall
  ptrace: Remove second setting of PT_SEIZED in ptrace_attach
  taskstats: Cleanup the use of task->exit_code
  exit: Use the correct exit_code in /proc//stat
  exit: Fix the exit_code for wait_task_zombie
  exit: Coredumps reach do_group_exit
  exit: Remove profile_handoff_task
  exit: Remove profile_task_exit & profile_munmap
  signal: clean up kernel-doc comments
  signal: Remove the helper signal_group_exit
  signal: Rename group_exit_task group_exec_task
  coredump: Stop setting signal->group_exit_task
  signal: Remove SIGNAL_GROUP_COREDUMP
  signal: During coredumps set SIGNAL_GROUP_EXIT in zap_process
  signal: Make coredump handling explicit in complete_signal
  signal: Have prepare_signal detect coredumps using signal->core_state
  signal: Have the oom killer detect coredumps using signal->core_state
  exit: Move force_uaccess back into do_exit
  exit: Guarantee make_task_dead leaks the tsk when calling do_task_exit
  ...

Merge tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-12T01:24:45+00:00

Pull locking updates from Borislav Petkov:
 "Lots of cleanups and preparation. Highlights:

   - futex: Cleanup and remove runtime futex_cmpxchg detection

   - rtmutex: Some fixes for the PREEMPT_RT locking infrastructure

   - kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
     annotate the racy owner->on_cpu access *once*.

   - atomic64: Dead-Code-Elemination"

[ Description above by Peter Zijlstra ]

* tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/atomic: atomic64: Remove unusable atomic ops
  futex: Fix additional regressions
  locking: Allow to include asm/spinlock_types.h from linux/spinlock_types_raw.h
  x86/mm: Include spinlock_t definition in pgtable.
  locking: Mark racy reads of owner->on_cpu
  locking: Make owner_on_cpu() into 
  lockdep/selftests: Adapt ww-tests for PREEMPT_RT
  lockdep/selftests: Skip the softirq related tests on PREEMPT_RT
  lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock().
  lockdep/selftests: Avoid using local_lock_{acquire|release}().
  lockdep: Remove softirq accounting on PREEMPT_RT.
  locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable().
  locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.
  locking: Remove rt_rwlock_is_contended().
  sched: Trigger warning if ->migration_disabled counter underflows.
  futex: Fix sparc32/m68k/nds32 build regression
  futex: Remove futex_cmpxchg detection
  futex: Ensure futex_atomic_cmpxchg_inatomic() is present
  kernel/locking: Use a pointer in ww_mutex_trylock().

Merge tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-01-12T01:14:59+00:00

Pull scheduler updates from Borislav Petkov:
 "Mostly minor things this time; some highlights:

   - core-sched: Add 'Forced Idle' accounting; this allows to track how
     much CPU time is 'lost' due to core scheduling constraints.

   - psi: Fix for MEM_FULL; a task running reclaim would be counted as a
     runnable task and prevent MEM_FULL from being reported.

   - cpuacct: Long standing fixes for some cgroup accounting issues.

   - rt: Bandwidth timer could, under unusual circumstances, be failed
     to armed, leading to indefinite throttling."

[ Description above by Peter Zijlstra ]

* tag 'sched_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Replace CFS internal cpu_util() with cpu_util_cfs()
  sched/fair: Cleanup task_util and capacity type
  sched/rt: Try to restart rt period timer when rt runtime exceeded
  sched/fair: Document the slow path and fast path in select_task_rq_fair
  sched/fair: Fix per-CPU kthread and wakee stacking for asym CPU capacity
  sched/fair: Fix detection of per-CPU kthreads waking a task
  sched/cpuacct: Make user/system times in cpuacct.stat more precise
  sched/cpuacct: Fix user/system in shown cpuacct.usage*
  cpuacct: Convert BUG_ON() to WARN_ON_ONCE()
  cputime, cpuacct: Include guest time in user time in cpuacct.stat
  psi: Fix PSI_MEM_FULL state when tasks are in memstall and doing reclaim
  sched/core: Forced idle accounting
  psi: Add a missing SPDX license header
  psi: Remove repeated verbose comment