20 Jun, 2017

3 commits

• 2055da973   sched/wait: Disambiguate wq_entry->task_list and wq_head->task_list naming ... Browse Code »

  So I've noticed a number of instances where it was not obvious from the
  code whether ->task_list was for a wait-queue head or a wait-queue entry.

  Furthermore, there's a number of wait-queue users where the lists are
  not for 'tasks' but other entities (poll tables, etc.), in which case
  the 'task_list' name is actively confusing.

  To clear this all up, name the wait-queue head and entry list structure
  fields unambiguously:

  struct wait_queue_head::task_list => ::head
  struct wait_queue_entry::task_list => ::entry

  For example, this code:

  rqw->wait.task_list.next != &wait->task_list

  ... is was pretty unclear (to me) what it's doing, while now it's written this way:

  rqw->wait.head.next != &wait->entry

  ... which makes it pretty clear that we are iterating a list until we see the head.

  Other examples are:

  list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
  list_for_each_entry(wq, &fence->wait.task_list, task_list) {

  ... where it's unclear (to me) what we are iterating, and during review it's
  hard to tell whether it's trying to walk a wait-queue entry (which would be
  a bug), while now it's written as:

  list_for_each_entry_safe(pos, next, &x->head, entry) {
  list_for_each_entry(wq, &fence->wait.head, entry) {

  Cc: Linus Torvalds
  Cc: Peter Zijlstra
  Cc: Thomas Gleixner
  Cc: linux-kernel@vger.kernel.org
  Signed-off-by: Ingo Molnar

  Ingo Molnar

  2017-06-20 18:19:14 +0800  
• 5822a454d   sched/wait: Move bit_wait_table[] and related functionality from sched/core.c to sched/wait_bit.c ... Browse Code »

  The key hashed waitqueue data structures and their initialization
  was done in the main scheduler file for no good reason, move them
  to sched/wait_bit.c instead.

  Cc: Linus Torvalds
  Cc: Peter Zijlstra
  Cc: Thomas Gleixner
  Cc: linux-kernel@vger.kernel.org
  Signed-off-by: Ingo Molnar

  Ingo Molnar

  2017-06-20 18:19:14 +0800  
• 5dd43ce2f   sched/wait: Split out the wait_bit*() APIs from <linux/wait.h> into <linux/wait_bit.h> ... Browse Code »

  The wait_bit*() types and APIs are mixed into wait.h, but they
  are a pretty orthogonal extension of wait-queues.

  Furthermore, only about 50 kernel files use these APIs, while
  over 1000 use the regular wait-queue functionality.

  So clean up the main wait.h by moving the wait-bit functionality
  out of it, into a separate .h and .c file:

  include/linux/wait_bit.h for types and APIs
  kernel/sched/wait_bit.c for the implementation

  Update all header dependencies.

  This reduces the size of wait.h rather significantly, by about 30%.

  Cc: Linus Torvalds
  Cc: Peter Zijlstra
  Cc: Thomas Gleixner
  Cc: linux-kernel@vger.kernel.org
  Signed-off-by: Ingo Molnar

  Ingo Molnar

  2017-06-20 18:19:09 +0800