[PATCH 0/8] mm: introduce for_each_process_rcu and for_each_thread_rcu

[Ye Liu]

From: Ye Liu <liuye@xxxxxxxxxx>

Introduce for_each_process_rcu(), for_each_thread_rcu() and
for_each_process_thread_rcu() macros that combine the existing
iteration macros with scoped_guard(rcu), so that the RCU read lock
is automatically acquired before iteration and released when the
loop exits — including via break, goto, or return.

The rest of the series converts manual rcu_read_lock()/
rcu_read_unlock() and guard(rcu)() pairs across mm/, kernel/, fs/,
lib/ and security/ to use the new macros.

Patch 1 may trigger checkpatch "Macros with complex values should be
enclosed in parentheses" errors.  These are false positives — the
scoped_guard() pattern is a control-flow construct, not a multi-
statement macro, and the same idiom is used elsewhere in the kernel.

Suggested by Michal Hocko for the oom_kill path [1].

[1] https://lore.kernel.org/all/20260813092933.562028-1-ye.liu@xxxxxxxxx/

Ye Liu (8):
  mm: introduce for_each_process_rcu and for_each_thread_rcu
  mm/oom_kill: convert process/thread iterators to for_each_*_rcu
  mm/ksm: convert process iterator to for_each_process_rcu
  mm/memory-failure: convert process iterator to for_each_process_rcu
  kernel: convert process/thread iterators to for_each_*_rcu
  fs: convert process/thread iterators to for_each_*_rcu
  lib: convert process iterator to for_each_process_rcu
  security/landlock: convert thread iterator to for_each_thread_rcu

 fs/proc/base.c               |  4 +---
 fs/resctrl/rdtgroup.c        |  8 ++------
 include/linux/sched/signal.h | 19 +++++++++++++++++++
 kernel/cpu.c                 |  4 +---
 kernel/freezer.c             |  4 +---
 kernel/hung_task.c           |  7 ++-----
 kernel/locking/lockdep.c     |  4 +---
 kernel/rcu/update.c          |  4 +---
 kernel/sched/core.c          |  3 +--
 kernel/sched/debug.c         |  4 +---
 kernel/trace/fgraph.c        |  8 ++------
 kernel/unwind/deferred.c     |  3 +--
 lib/is_single_threaded.c     |  5 +----
 mm/ksm.c                     |  4 +---
 mm/memory-failure.c          | 16 ++++------------
 mm/oom_kill.c                | 20 +++++---------------
 security/landlock/tsync.c    |  8 ++------
 17 files changed, 46 insertions(+), 79 deletions(-)

Signed-off-by: Ye Liu <liuye@xxxxxxxxxx>

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2.25.1