linux-toradex.git/include/linux/sched.h, branch v5.12-rc5 Linux kernel for Apalis and Colibri modules io-wq: fork worker threads from original task 2021-02-22T00:25:22+00:00 Jens Axboe axboe@kernel.dk 2021-02-16T21:15:30+00:00 3bfe6106693b6b4ba175ad1f929c4660b8f59ca8 Instead of using regular kthread kernel threads, create kernel threads that are like a real thread that the task would create. This ensures that we get all the context that we need, without having to carry that state around. This greatly reduces the code complexity, and the risk of missing state for a given request type. With the move away from kthread, we can also dump everything related to assigned state to the new threads. Signed-off-by: Jens Axboe <axboe@kernel.dk> 
Instead of using regular kthread kernel threads, create kernel threads
that are like a real thread that the task would create. This ensures that
we get all the context that we need, without having to carry that state
around. This greatly reduces the code complexity, and the risk of missing
state for a given request type.

With the move away from kthread, we can also dump everything related to
assigned state to the new threads.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2021-02-21T21:31:43+00:00 Linus Torvalds torvalds@linux-foundation.org 2021-02-21T21:31:43+00:00 3e10585335b7967326ca7b4118cada0d2d00a2ab Pull KVM updates from Paolo Bonzini: "x86: - Support for userspace to emulate Xen hypercalls - Raise the maximum number of user memslots - Scalability improvements for the new MMU. Instead of the complex "fast page fault" logic that is used in mmu.c, tdp_mmu.c uses an rwlock so that page faults are concurrent, but the code that can run against page faults is limited. Right now only page faults take the lock for reading; in the future this will be extended to some cases of page table destruction. I hope to switch the default MMU around 5.12-rc3 (some testing was delayed due to Chinese New Year). - Cleanups for MAXPHYADDR checks - Use static calls for vendor-specific callbacks - On AMD, use VMLOAD/VMSAVE to save and restore host state - Stop using deprecated jump label APIs - Workaround for AMD erratum that made nested virtualization unreliable - Support for LBR emulation in the guest - Support for communicating bus lock vmexits to userspace - Add support for SEV attestation command - Miscellaneous cleanups PPC: - Support for second data watchpoint on POWER10 - Remove some complex workarounds for buggy early versions of POWER9 - Guest entry/exit fixes ARM64: - Make the nVHE EL2 object relocatable - Cleanups for concurrent translation faults hitting the same page - Support for the standard TRNG hypervisor call - A bunch of small PMU/Debug fixes - Simplification of the early init hypercall handling Non-KVM changes (with acks): - Detection of contended rwlocks (implemented only for qrwlocks, because KVM only needs it for x86) - Allow __DISABLE_EXPORTS from assembly code - Provide a saner follow_pfn replacements for modules" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (192 commits) KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64 bytes KVM: selftests: Don't bother mapping GVA for Xen shinfo test KVM: selftests: Fix hex vs. decimal snafu in Xen test KVM: selftests: Fix size of memslots created by Xen tests KVM: selftests: Ignore recently added Xen tests' build output KVM: selftests: Add missing header file needed by xAPIC IPI tests KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c KVM: SVM: Make symbol 'svm_gp_erratum_intercept' static locking/arch: Move qrwlock.h include after qspinlock.h KVM: PPC: Book3S HV: Fix host radix SLB optimisation with hash guests KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries KVM: PPC: Don't always report hash MMU capability for P9 < DD2.2 KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path KVM: PPC: remove unneeded semicolon KVM: PPC: Book3S HV: Use POWER9 SLBIA IH=6 variant to clear SLB KVM: PPC: Book3S HV: No need to clear radix host SLB before loading HPT guest KVM: PPC: Book3S HV: Fix radix guest SLB side channel KVM: PPC: Book3S HV: Remove support for running HPT guest on RPT host without mixed mode support KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR KVM: PPC: Book3S HV: Add infrastructure to support 2nd DAWR ... 
Pull KVM updates from Paolo Bonzini:
 "x86:

   - Support for userspace to emulate Xen hypercalls

   - Raise the maximum number of user memslots

   - Scalability improvements for the new MMU.

     Instead of the complex "fast page fault" logic that is used in
     mmu.c, tdp_mmu.c uses an rwlock so that page faults are concurrent,
     but the code that can run against page faults is limited. Right now
     only page faults take the lock for reading; in the future this will
     be extended to some cases of page table destruction. I hope to
     switch the default MMU around 5.12-rc3 (some testing was delayed
     due to Chinese New Year).

   - Cleanups for MAXPHYADDR checks

   - Use static calls for vendor-specific callbacks

   - On AMD, use VMLOAD/VMSAVE to save and restore host state

   - Stop using deprecated jump label APIs

   - Workaround for AMD erratum that made nested virtualization
     unreliable

   - Support for LBR emulation in the guest

   - Support for communicating bus lock vmexits to userspace

   - Add support for SEV attestation command

   - Miscellaneous cleanups

  PPC:

   - Support for second data watchpoint on POWER10

   - Remove some complex workarounds for buggy early versions of POWER9

   - Guest entry/exit fixes

  ARM64:

   - Make the nVHE EL2 object relocatable

   - Cleanups for concurrent translation faults hitting the same page

   - Support for the standard TRNG hypervisor call

   - A bunch of small PMU/Debug fixes

   - Simplification of the early init hypercall handling

  Non-KVM changes (with acks):

   - Detection of contended rwlocks (implemented only for qrwlocks,
     because KVM only needs it for x86)

   - Allow __DISABLE_EXPORTS from assembly code

   - Provide a saner follow_pfn replacements for modules"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (192 commits)
  KVM: x86/xen: Explicitly pad struct compat_vcpu_info to 64 bytes
  KVM: selftests: Don't bother mapping GVA for Xen shinfo test
  KVM: selftests: Fix hex vs. decimal snafu in Xen test
  KVM: selftests: Fix size of memslots created by Xen tests
  KVM: selftests: Ignore recently added Xen tests' build output
  KVM: selftests: Add missing header file needed by xAPIC IPI tests
  KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c
  KVM: SVM: Make symbol 'svm_gp_erratum_intercept' static
  locking/arch: Move qrwlock.h include after qspinlock.h
  KVM: PPC: Book3S HV: Fix host radix SLB optimisation with hash guests
  KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries
  KVM: PPC: Don't always report hash MMU capability for P9 < DD2.2
  KVM: PPC: Book3S HV: Save and restore FSCR in the P9 path
  KVM: PPC: remove unneeded semicolon
  KVM: PPC: Book3S HV: Use POWER9 SLBIA IH=6 variant to clear SLB
  KVM: PPC: Book3S HV: No need to clear radix host SLB before loading HPT guest
  KVM: PPC: Book3S HV: Fix radix guest SLB side channel
  KVM: PPC: Book3S HV: Remove support for running HPT guest on RPT host without mixed mode support
  KVM: PPC: Book3S HV: Introduce new capability for 2nd DAWR
  KVM: PPC: Book3S HV: Add infrastructure to support 2nd DAWR
  ...
sched: Harden PREEMPT_DYNAMIC 2021-02-17T13:12:42+00:00 Peter Zijlstra peterz@infradead.org 2021-01-25T15:26:50+00:00 ef72661e28c64ad610f89acc2832ec67b27ba438 Use the new EXPORT_STATIC_CALL_TRAMP() / static_call_mod() to unexport the static_call_key for the PREEMPT_DYNAMIC calls such that modules can no longer update these calls. Having modules change/hi-jack the preemption calls would be horrible. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> 
Use the new EXPORT_STATIC_CALL_TRAMP() / static_call_mod() to unexport
the static_call_key for the PREEMPT_DYNAMIC calls such that modules
can no longer update these calls.

Having modules change/hi-jack the preemption calls would be horrible.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
preempt/dynamic: Provide cond_resched() and might_resched() static calls 2021-02-17T13:12:42+00:00 Peter Zijlstra (Intel) peterz@infradead.org 2021-01-18T14:12:20+00:00 b965f1ddb47daa5b8b2e2bc9c921431236830367 Provide static calls to control cond_resched() (called in !CONFIG_PREEMPT) and might_resched() (called in CONFIG_PREEMPT_VOLUNTARY) to that we can override their behaviour when preempt= is overriden. Since the default behaviour is full preemption, both their calls are ignored when preempt= isn't passed. [fweisbec: branch might_resched() directly to __cond_resched(), only define static calls when PREEMPT_DYNAMIC] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20210118141223.123667-6-frederic@kernel.org 
Provide static calls to control cond_resched() (called in !CONFIG_PREEMPT)
and might_resched() (called in CONFIG_PREEMPT_VOLUNTARY) to that we
can override their behaviour when preempt= is overriden.

Since the default behaviour is full preemption, both their calls are
ignored when preempt= isn't passed.

  [fweisbec: branch might_resched() directly to __cond_resched(), only
             define static calls when PREEMPT_DYNAMIC]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210118141223.123667-6-frederic@kernel.org
sched: Add cond_resched_rwlock 2021-02-04T10:27:43+00:00 Ben Gardon bgardon@google.com 2021-02-02T18:57:14+00:00 f3d4b4b1dc1c5fb9ea17cac14133463bfe72f170 Safely rescheduling while holding a spin lock is essential for keeping long running kernel operations running smoothly. Add the facility to cond_resched rwlocks. CC: Ingo Molnar <mingo@redhat.com> CC: Will Deacon <will@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Davidlohr Bueso <dbueso@suse.de> Acked-by: Waiman Long <longman@redhat.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Ben Gardon <bgardon@google.com> Message-Id: <20210202185734.1680553-9-bgardon@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> 
Safely rescheduling while holding a spin lock is essential for keeping
long running kernel operations running smoothly. Add the facility to
cond_resched rwlocks.

CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-9-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
sched: Add needbreak for rwlocks 2021-02-04T10:27:43+00:00 Ben Gardon bgardon@google.com 2021-02-02T18:57:13+00:00 a09a689a534183c48f200bc2de1ae61ae9c462ad Contention awareness while holding a spin lock is essential for reducing latency when long running kernel operations can hold that lock. Add the same contention detection interface for read/write spin locks. CC: Ingo Molnar <mingo@redhat.com> CC: Will Deacon <will@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Davidlohr Bueso <dbueso@suse.de> Acked-by: Waiman Long <longman@redhat.com> Acked-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Ben Gardon <bgardon@google.com> Message-Id: <20210202185734.1680553-8-bgardon@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> 
Contention awareness while holding a spin lock is essential for reducing
latency when long running kernel operations can hold that lock. Add the
same contention detection interface for read/write spin locks.

CC: Ingo Molnar <mingo@redhat.com>
CC: Will Deacon <will@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-8-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
sched: Correctly sort struct predeclarations 2021-01-27T16:26:43+00:00 Peter Oskolkov posk@google.com 2021-01-26T19:34:49+00:00 1875dc5b8ff4690547c446ef222083e28e2d9463 The comment says: /* task_struct member predeclarations (sorted alphabetically): */ So move io_uring_task where it belongs (alphabetically). Signed-off-by: Peter Oskolkov <posk@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20210126193449.487547-1-posk@google.com 
The comment says:
  /* task_struct member predeclarations (sorted alphabetically): */

So move io_uring_task where it belongs (alphabetically).

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210126193449.487547-1-posk@google.com
sched/core: Rename schedutil_cpu_util() and allow rest of the kernel to use it 2021-01-14T10:20:09+00:00 Viresh Kumar viresh.kumar@linaro.org 2020-12-08T04:16:56+00:00 a5418be9dffe70ccbb0b4bd5ea3881c81927e965 There is nothing schedutil specific in schedutil_cpu_util(), rename it to effective_cpu_util(). Also create and expose another wrapper sched_cpu_util() which can be used by other parts of the kernel, like thermal core (that will be done in a later commit). Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Link: https://lkml.kernel.org/r/db011961fb3bb8bef1c0eda5cd64564637d3ef31.1607400596.git.viresh.kumar@linaro.org 
There is nothing schedutil specific in schedutil_cpu_util(), rename it
to effective_cpu_util(). Also create and expose another wrapper
sched_cpu_util() which can be used by other parts of the kernel, like
thermal core (that will be done in a later commit).

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/db011961fb3bb8bef1c0eda5cd64564637d3ef31.1607400596.git.viresh.kumar@linaro.org
kasan, arm64: only use kasan_depth for software modes 2020-12-22T20:55:07+00:00 Andrey Konovalov andreyknvl@google.com 2020-12-22T20:00:56+00:00 d73b49365ee65ac48074bdb5aa717bb4644dbbb7 This is a preparatory commit for the upcoming addition of a new hardware tag-based (MTE-based) KASAN mode. Hardware tag-based KASAN won't use kasan_depth. Only define and use it when one of the software KASAN modes are enabled. No functional changes for software modes. Link: https://lkml.kernel.org/r/e16f15aeda90bc7fb4dfc2e243a14b74cc5c8219.1606161801.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Alexander Potapenko <glider@google.com> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Branislav Rankov <Branislav.Rankov@arm.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Marco Elver <elver@google.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
This is a preparatory commit for the upcoming addition of a new hardware
tag-based (MTE-based) KASAN mode.

Hardware tag-based KASAN won't use kasan_depth.  Only define and use it
when one of the software KASAN modes are enabled.

No functional changes for software modes.

Link: https://lkml.kernel.org/r/e16f15aeda90bc7fb4dfc2e243a14b74cc5c8219.1606161801.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Branislav Rankov <Branislav.Rankov@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Marco Elver <elver@google.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2020-12-15T02:35:53+00:00 Linus Torvalds torvalds@linux-foundation.org 2020-12-15T02:35:53+00:00 edd7ab76847442e299af64a761febd180d71f98d Pull kmap updates from Thomas Gleixner: "The new preemtible kmap_local() implementation: - Consolidate all kmap_atomic() internals into a generic implementation which builds the base for the kmap_local() API and make the kmap_atomic() interface wrappers which handle the disabling/enabling of preemption and pagefaults. - Switch the storage from per-CPU to per task and provide scheduler support for clearing mapping when scheduling out and restoring them when scheduling back in. - Merge the migrate_disable/enable() code, which is also part of the scheduler pull request. This was required to make the kmap_local() interface available which does not disable preemption when a mapping is established. It has to disable migration instead to guarantee that the virtual address of the mapped slot is the same across preemption. - Provide better debug facilities: guard pages and enforced utilization of the mapping mechanics on 64bit systems when the architecture allows it. - Provide the new kmap_local() API which can now be used to cleanup the kmap_atomic() usage sites all over the place. Most of the usage sites do not require the implicit disabling of preemption and pagefaults so the penalty on 64bit and 32bit non-highmem systems is removed and quite some of the code can be simplified. A wholesale conversion is not possible because some usage depends on the implicit side effects and some need to be cleaned up because they work around these side effects. The migrate disable side effect is only effective on highmem systems and when enforced debugging is enabled. On 64bit and 32bit non-highmem systems the overhead is completely avoided" * tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) ARM: highmem: Fix cache_is_vivt() reference x86/crashdump/32: Simplify copy_oldmem_page() io-mapping: Provide iomap_local variant mm/highmem: Provide kmap_local* sched: highmem: Store local kmaps in task struct x86: Support kmap_local() forced debugging mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL microblaze/mm/highmem: Add dropped #ifdef back xtensa/mm/highmem: Make generic kmap_atomic() work correctly mm/highmem: Take kmap_high_get() properly into account highmem: High implementation details and document API Documentation/io-mapping: Remove outdated blurb io-mapping: Cleanup atomic iomap mm/highmem: Remove the old kmap_atomic cruft highmem: Get rid of kmap_types.h xtensa/mm/highmem: Switch to generic kmap atomic sparc/mm/highmem: Switch to generic kmap atomic powerpc/mm/highmem: Switch to generic kmap atomic nds32/mm/highmem: Switch to generic kmap atomic ... 
Pull kmap updates from Thomas Gleixner:
 "The new preemtible kmap_local() implementation:

   - Consolidate all kmap_atomic() internals into a generic
     implementation which builds the base for the kmap_local() API and
     make the kmap_atomic() interface wrappers which handle the
     disabling/enabling of preemption and pagefaults.

   - Switch the storage from per-CPU to per task and provide scheduler
     support for clearing mapping when scheduling out and restoring them
     when scheduling back in.

   - Merge the migrate_disable/enable() code, which is also part of the
     scheduler pull request. This was required to make the kmap_local()
     interface available which does not disable preemption when a
     mapping is established. It has to disable migration instead to
     guarantee that the virtual address of the mapped slot is the same
     across preemption.

   - Provide better debug facilities: guard pages and enforced
     utilization of the mapping mechanics on 64bit systems when the
     architecture allows it.

   - Provide the new kmap_local() API which can now be used to cleanup
     the kmap_atomic() usage sites all over the place. Most of the usage
     sites do not require the implicit disabling of preemption and
     pagefaults so the penalty on 64bit and 32bit non-highmem systems is
     removed and quite some of the code can be simplified. A wholesale
     conversion is not possible because some usage depends on the
     implicit side effects and some need to be cleaned up because they
     work around these side effects.

     The migrate disable side effect is only effective on highmem
     systems and when enforced debugging is enabled. On 64bit and 32bit
     non-highmem systems the overhead is completely avoided"

* tag 'core-mm-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
  ARM: highmem: Fix cache_is_vivt() reference
  x86/crashdump/32: Simplify copy_oldmem_page()
  io-mapping: Provide iomap_local variant
  mm/highmem: Provide kmap_local*
  sched: highmem: Store local kmaps in task struct
  x86: Support kmap_local() forced debugging
  mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
  mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL
  microblaze/mm/highmem: Add dropped #ifdef back
  xtensa/mm/highmem: Make generic kmap_atomic() work correctly
  mm/highmem: Take kmap_high_get() properly into account
  highmem: High implementation details and document API
  Documentation/io-mapping: Remove outdated blurb
  io-mapping: Cleanup atomic iomap
  mm/highmem: Remove the old kmap_atomic cruft
  highmem: Get rid of kmap_types.h
  xtensa/mm/highmem: Switch to generic kmap atomic
  sparc/mm/highmem: Switch to generic kmap atomic
  powerpc/mm/highmem: Switch to generic kmap atomic
  nds32/mm/highmem: Switch to generic kmap atomic
  ...