[PATCH v4 00/22] kthread: Use kthread worker API more widely

[Petr Mladek]

My intention is to make it easier to manipulate and maintain kthreads.
Especially, I want to replace all the custom main cycles with a
generic one. Also I want to make the kthreads sleep in a consistent
state in a common place when there is no work.

My first attempt was with a brand new API (iterant kthread), see
http://thread.gmane.org/gmane.linux.kernel.api/11892 . But I was
directed to improve the existing kthread worker API. This is
the 3rd iteration of the new direction.


1st patch: add support to check if a timer callback is being called

2nd..12th patches: improve the existing kthread worker API

13th..18th, 20th, 22nd patches: convert several kthreads into
      the kthread worker API, namely: khugepaged, ring buffer
      benchmark, hung_task, kmemleak, ipmi, IB/fmr_pool,
      memstick/r592, intel_powerclamp
      
19th, 21st patches: do some preparation steps; they usually do
      some clean up that makes sense even without the conversion.


Changes against v3:

  + allow to free struct kthread_work from its callback; do not touch
    the struct from the worker post-mortem; as a side effect, the structure
    must be reinitialized when the worker gets restarted; updated
    khugepaged, and kmemleak accordingly

  + call del_timer_sync() with worker->lock; instead, detect canceling
    in the timer callback and give up an attempt to get the lock there;
    do busy loop with spin_is_locked() to reduce cache bouncing

  + renamed ipmi+func() -> ipmi_kthread_worker_func() as suggested
    by Corey

  + added some collected Reviewed-by

  
Changes against v2:

  + used worker->lock to synchronize the operations with the work
    instead of the PENDING bit as suggested by Tejun Heo; it simplified
    the implementation in several ways

  + added timer_active(); used it together with del_timer_sync()
    to cancel the work a less tricky way

  + removed the controversial conversion of the RCU kthreads

  + added several other examples: hung_task, kmemleak, ipmi,
    IB/fmr_pool, memstick/r592, intel_powerclamp

  + the helper fixes for the ring buffer benchmark has been improved
    as suggested by Steven; they already are in the Linus tree now

  + fixed a possible race between the check for existing khugepaged
    worker and queuing the work
 

Changes against v1:

  + remove wrappers to manipulate the scheduling policy and priority

  + remove questionable wakeup_and_destroy_kthread_worker() variant

  + do not check for chained work when draining the queue

  + allocate struct kthread worker in create_kthread_work() and
    use more simple checks for running worker

  + add support for delayed kthread works and use them instead
    of waiting inside the works

  + rework the "unrelated" fixes for the ring buffer benchmark
    as discussed in the 1st RFC; also sent separately

  + convert also the consumer in the ring buffer benchmark


I have tested this patch set against the stable Linus tree
for 4.5-rc1.

Comments against v3 can be found at
http://thread.gmane.org/gmane.linux.kernel.mm/141493


Petr Mladek (22):
  timer: Allow to check when the timer callback has not finished yet
  kthread/smpboot: Do not park in kthread_create_on_cpu()
  kthread: Allow to call __kthread_create_on_node() with va_list args
  kthread: Add create_kthread_worker*()
  kthread: Add drain_kthread_worker()
  kthread: Add destroy_kthread_worker()
  kthread: Detect when a kthread work is used by more workers
  kthread: Initial support for delayed kthread work
  kthread: Allow to cancel kthread work
  kthread: Allow to modify delayed kthread work
  kthread: Better support freezable kthread workers
  kthread: Use try_lock_kthread_work() in flush_kthread_work()
  mm/huge_page: Convert khugepaged() into kthread worker API
  ring_buffer: Convert benchmark kthreads into kthread worker API
  hung_task: Convert hungtaskd into kthread worker API
  kmemleak: Convert kmemleak kthread into kthread worker API
  ipmi: Convert kipmi kthread into kthread worker API
  IB/fmr_pool: Convert the cleanup thread into kthread worker API
  memstick/r592: Better synchronize debug messages in r592_io kthread
  memstick/r592: convert r592_io kthread into kthread worker API
  thermal/intel_powerclamp: Remove duplicated code that starts the
    kthread
  thermal/intel_powerclamp: Convert the kthread to kthread worker API

 drivers/char/ipmi/ipmi_si_intf.c     | 121 ++++---
 drivers/infiniband/core/fmr_pool.c   |  54 ++-
 drivers/memstick/host/r592.c         |  61 ++--
 drivers/memstick/host/r592.h         |   5 +-
 drivers/thermal/intel_powerclamp.c   | 302 +++++++++--------
 include/linux/kthread.h              |  56 ++++
 include/linux/timer.h                |   2 +
 kernel/hung_task.c                   |  41 ++-
 kernel/kthread.c                     | 619 +++++++++++++++++++++++++++++++----
 kernel/smpboot.c                     |   5 +
 kernel/time/timer.c                  |  24 ++
 kernel/trace/ring_buffer_benchmark.c | 133 ++++----
 mm/huge_memory.c                     | 138 ++++----
 mm/kmemleak.c                        |  87 +++--
 14 files changed, 1151 insertions(+), 497 deletions(-)

CC: Catalin Marinas <catalin.marinas@xxxxxxx>
CC: linux-watchdog@xxxxxxxxxxxxxxx
CC: Corey Minyard <minyard@xxxxxxx>
CC: openipmi-developer@xxxxxxxxxxxxxxxxxxxxx
CC: Doug Ledford <dledford@xxxxxxxxxx>
CC: Sean Hefty <sean.hefty@xxxxxxxxx>
CC: Hal Rosenstock <hal.rosenstock@xxxxxxxxx>
CC: linux-rdma@xxxxxxxxxxxxxxx
CC: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
CC: Zhang Rui <rui.zhang@xxxxxxxxx>
CC: Eduardo Valentin <edubezval@xxxxxxxxx>
CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
CC: linux-pm@xxxxxxxxxxxxxxx

-- 
1.8.5.6