linux-toradex.git/include/linux/rcupdate.h, branch v6.6-rc3

Merge tag 'core_guards_for_6.5_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue

2023-07-04T20:50:38+00:00

Pull scope-based resource management infrastructure from Peter Zijlstra:
 "These are the first few patches in the Scope-based Resource Management
  series that introduce the infrastructure but not any conversions as of
  yet.

  Adding the infrastructure now allows multiple people to start using
  them.

  Of note is that Sparse will need some work since it doesn't yet
  understand this attribute and might have decl-after-stmt issues"

* tag 'core_guards_for_6.5_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue:
  kbuild: Drop -Wdeclaration-after-statement
  locking: Introduce __cleanup() based infrastructure
  apparmor: Free up __cleanup() name
  dmaengine: ioat: Free up __cleanup() name

locking: Introduce __cleanup() based infrastructure

2023-06-26T09:14:18+00:00

Use __attribute__((__cleanup__(func))) to build:

 - simple auto-release pointers using __free()

 - 'classes' with constructor and destructor semantics for
   scope-based resource management.

 - lock guards based on the above classes.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20230612093537.614161713%40infradead.org

Merge branches 'doc.2023.05.10a', 'fixes.2023.05.11a', 'kvfree.2023.05.10a', 'nocb.2023.05.11a', 'rcu-tasks.2023.05.10a', 'torture.2023.05.15a' and 'rcu-urgent.2023.06.06a' into HEAD

2023-06-07T20:44:06+00:00

doc.2023.05.10a: Documentation updates
fixes.2023.05.11a: Miscellaneous fixes
kvfree.2023.05.10a: kvfree_rcu updates
nocb.2023.05.11a: Callback-offloading updates
rcu-tasks.2023.05.10a: Tasks RCU updates
torture.2023.05.15a: Torture-test updates
rcu-urgent.2023.06.06a: Urgent SRCU fix

rcu: Remove RCU_NONIDLE()

2023-05-11T20:42:04+00:00

Since there are now exactly _zero_ users of RCU_NONIDLE(), make it go
away before someone else decides to (ab)use it.

[ paulmck: Remove extraneous whitespace. ]

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Mark Rutland 
Acked-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney

rcu/kvfree: Eliminate k[v]free_rcu() single argument macro

2023-05-10T00:26:20+00:00

The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget
the second argument, it works, but might sleep.  This sleeping can be a
correctness bug from atomic contexts, and even in non-atomic contexts it
might introduce unacceptable latencies.  This commit therefore removes the
single-argument kvfree_rcu() and kfree_rcu() macros.  Code that would have
previously used these single-argument kvfree_rcu() and kfree_rcu() macros
should instead use kvfree_rcu_mightsleep() or kfree_rcu_mightsleep().

[ paulmck: Apply Joel Fernandes feedback. ]

Signed-off-by: Uladzislau Rezki (Sony) 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Joel Fernandes (Google)

mm/slab: document kfree() as allowed for kmem_cache_alloc() objects

2023-03-29T08:35:41+00:00

This will make it easier to free objects in situations when they can
come from either kmalloc() or kmem_cache_alloc(), and also allow
kfree_rcu() for freeing objects from kmem_cache_alloc().

For the SLAB and SLUB allocators this was always possible so with SLOB
gone, we can document it as supported.

Signed-off-by: Vlastimil Babka 
Reviewed-by: Mike Rapoport (IBM) 
Cc: Jonathan Corbet 
Cc: "Paul E. McKenney" 
Cc: Frederic Weisbecker 
Cc: Neeraj Upadhyay 
Cc: Josh Triplett 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Joel Fernandes

Merge branches 'doc.2023.01.05a', 'fixes.2023.01.23a', 'kvfree.2023.01.03a', 'srcu.2023.01.03a', 'srcu-always.2023.02.02a', 'tasks.2023.01.03a', 'torture.2023.01.05a' and 'torturescript.2023.01.03a' into HEAD

2023-02-03T00:33:43+00:00

doc.2023.01.05a: Documentation update.
fixes.2023.01.23a: Miscellaneous fixes.
kvfree.2023.01.03a: kvfree_rcu() updates.
srcu.2023.01.03a: SRCU updates.
srcu-always.2023.02.02a: Finish making SRCU be unconditionally available.
tasks.2023.01.03a: Tasks-RCU updates.
torture.2023.01.05a: Torture-test updates.
torturescript.2023.01.03a: Torture-test scripting updates.

rcu/kvfree: Add kvfree_rcu_mightsleep() and kfree_rcu_mightsleep()

2023-02-03T00:28:07+00:00

The kvfree_rcu() and kfree_rcu() APIs are hazardous in that if you forget
the second argument, it works, but might sleep.  This sleeping can be a
correctness bug from atomic contexts, and even in non-atomic contexts
it might introduce unacceptable latencies.  This commit therefore adds
kvfree_rcu_mightsleep() and kfree_rcu_mightsleep(), which will replace
the single-argument kvfree_rcu() and kfree_rcu(), respectively.

This commit enables a series of commits that switch from single-argument
kvfree_rcu() and kfree_rcu() to their _mightsleep() counterparts.  Once
all of these commits land, the single-argument versions will be removed.

Signed-off-by: Uladzislau Rezki (Sony) 
Signed-off-by: Paul E. McKenney

rcu-tasks: Fix synchronize_rcu_tasks() VS zap_pid_ns_processes()

2023-01-04T01:52:16+00:00

RCU Tasks and PID-namespace unshare can interact in do_exit() in a
complicated circular dependency:

1) TASK A calls unshare(CLONE_NEWPID), this creates a new PID namespace
   that every subsequent child of TASK A will belong to. But TASK A
   doesn't itself belong to that new PID namespace.

2) TASK A forks() and creates TASK B. TASK A stays attached to its PID
   namespace (let's say PID_NS1) and TASK B is the first task belonging
   to the new PID namespace created by unshare()  (let's call it PID_NS2).

3) Since TASK B is the first task attached to PID_NS2, it becomes the
   PID_NS2 child reaper.

4) TASK A forks() again and creates TASK C which get attached to PID_NS2.
   Note how TASK C has TASK A as a parent (belonging to PID_NS1) but has
   TASK B (belonging to PID_NS2) as a pid_namespace child_reaper.

5) TASK B exits and since it is the child reaper for PID_NS2, it has to
   kill all other tasks attached to PID_NS2, and wait for all of them to
   die before getting reaped itself (zap_pid_ns_process()).

6) TASK A calls synchronize_rcu_tasks() which leads to
   synchronize_srcu(&tasks_rcu_exit_srcu).

7) TASK B is waiting for TASK C to get reaped. But TASK B is under a
   tasks_rcu_exit_srcu SRCU critical section (exit_notify() is between
   exit_tasks_rcu_start() and exit_tasks_rcu_finish()), blocking TASK A.

8) TASK C exits and since TASK A is its parent, it waits for it to reap
   TASK C, but it can't because TASK A waits for TASK B that waits for
   TASK C.

Pid_namespace semantics can hardly be changed at this point. But the
coverage of tasks_rcu_exit_srcu can be reduced instead.

The current task is assumed not to be concurrently reapable at this
stage of exit_notify() and therefore tasks_rcu_exit_srcu can be
temporarily relaxed without breaking its constraints, providing a way
out of the deadlock scenario.

[ paulmck: Fix build failure by adding additional declaration. ]

Fixes: 3f95aa81d265 ("rcu: Make TASKS_RCU handle tasks that are almost done exiting")
Reported-by: Pengfei Xu 
Suggested-by: Boqun Feng 
Suggested-by: Neeraj Upadhyay 
Suggested-by: Paul E. McKenney 
Cc: Oleg Nesterov 
Cc: Lai Jiangshan 
Cc: Eric W . Biederman 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney

rcu: Refactor kvfree_call_rcu() and high-level helpers

2023-01-04T01:48:40+00:00

Currently a kvfree_call_rcu() takes an offset within a structure as
a second parameter, so a helper such as a kvfree_rcu_arg_2() has to
convert rcu_head and a freed ptr to an offset in order to pass it. That
leads to an extra conversion on macro entry.

Instead of converting, refactor the code in way that a pointer that has
to be freed is passed directly to the kvfree_call_rcu().

This patch does not make any functional change and is transparent to
all kvfree_rcu() users.

Signed-off-by: Uladzislau Rezki (Sony) 
Signed-off-by: Paul E. McKenney