linux-toradex.git/include/linux/rcupdate.h, branch v5.8-rc3

rcu-tasks: Make RCU Tasks Trace make use of RCU scheduler hooks

2020-04-27T18:03:52+00:00

This commit makes the calls to rcu_tasks_qs() detect and report
quiescent states for RCU tasks trace.  If the task is in a quiescent
state and if ->trc_reader_checked is not yet set, the task sets its own
->trc_reader_checked.  This will cause the grace-period kthread to
remove it from the holdout list if it still remains there.

[ paulmck: Fix conditional compilation per kbuild test robot feedback. ]
Signed-off-by: Paul E. McKenney

rcu-tasks: Add an RCU-tasks rude variant

2020-04-27T18:03:51+00:00

This commit adds a "rude" variant of RCU-tasks that has as quiescent
states schedule(), cond_resched_tasks_rcu_qs(), userspace execution,
and (in theory, anyway) cond_resched().  In other words, RCU-tasks rude
readers are regions of code with preemption disabled, but excluding code
early in the CPU-online sequence and late in the CPU-offline sequence.
Updates make use of IPIs and force an IPI and a context switch on each
online CPU.  This variant is useful in some situations in tracing.

Suggested-by: Steven Rostedt 
[ paulmck: Apply EXPORT_SYMBOL_GPL() feedback from Qiujun Huang. ]
Signed-off-by: Paul E. McKenney 
[ paulmck: Apply review feedback from Steve Rostedt. ]

rcu-tasks: Refactor RCU-tasks to allow variants to be added

2020-04-27T18:03:51+00:00

This commit splits out generic processing from RCU-tasks-specific
processing in order to allow additional flavors to be added.  It also
adds a def_bool TASKS_RCU_GENERIC to enable the common RCU-tasks
infrastructure code.

This is primarily, but not entirely, a code-movement commit.

Signed-off-by: Paul E. McKenney

Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD

2020-01-24T18:37:27+00:00

doc.2019.12.10a: Documentations updates
exp.2019.12.09a: Expedited grace-period updates
fixes.2020.01.24a: Miscellaneous fixes
kfree_rcu.2020.01.24a: Batch kfree_rcu() work
list.2020.01.10a: RCU-protected-list updates
preempt.2020.01.24a: Preemptible RCU updates
torture.2019.12.09a: Torture-test updates

rcu: Move rcu_{expedited,normal} definitions into rcupdate.h

2020-01-24T18:33:50+00:00

This commit moves the rcu_{expedited,normal} definitions from
kernel/rcu/update.c to include/linux/rcupdate.h to make sure they are
in sync, and also to avoid the following warning from sparse:

kernel/ksysfs.c:150:5: warning: symbol 'rcu_expedited' was not declared. Should it be static?
kernel/ksysfs.c:167:5: warning: symbol 'rcu_normal' was not declared. Should it be static?

Signed-off-by: Ben Dooks 
Signed-off-by: Paul E. McKenney

rcu: Remove rcu_swap_protected()

2019-12-12T18:24:52+00:00

Now that the calls to rcu_swap_protected() have been replaced by
rcu_replace_pointer(), this commit removes rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds 
Signed-off-by: Paul E. McKenney 
Cc: Bart Van Assche 
Cc: Christoph Hellwig 
Cc: Hannes Reinecke 
Cc: Johannes Thumshirn 
Cc: Shane M Seymour 
Cc: Martin K. Petersen

rcu: Use CONFIG_PREEMPTION where appropriate

2019-12-09T20:37:51+00:00

The config option `CONFIG_PREEMPT' is used for the preemption model
"Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled
when kernel preemption is enabled which is true for the preemption model
`CONFIG_PREEMPT' and `CONFIG_PREEMPT_RT'.

Use `CONFIG_PREEMPTION' if it applies to both preemption models and not
just to `CONFIG_PREEMPT'.

Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Joel Fernandes 
Cc: Davidlohr Bueso 
Cc: rcu@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Paul E. McKenney

rcu: Make PREEMPT_RCU be a modifier to TREE_RCU

2019-12-09T20:37:51+00:00

Currently PREEMPT_RCU and TREE_RCU are mutually exclusive Kconfig
options.  But PREEMPT_RCU actually specifies a kind of TREE_RCU,
namely a preemptible TREE_RCU. This commit therefore makes PREEMPT_RCU
be a modifer to the TREE_RCU Kconfig option.  This has the benefit of
simplifying several of the #if expressions that formerly needed to
check both, but now need only check one or the other.

Signed-off-by: Lai Jiangshan 
Signed-off-by: Lai Jiangshan 
Reviewed-by: Joel Fernandes (Google) 
Signed-off-by: Paul E. McKenney

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-11-27T00:02:40+00:00

Pull locking updates from Ingo Molnar:
 "The main changes in this cycle were:

   - A comprehensive rewrite of the robust/PI futex code's exit handling
     to fix various exit races. (Thomas Gleixner et al)

   - Rework the generic REFCOUNT_FULL implementation using
     atomic_fetch_* operations so that the performance impact of the
     cmpxchg() loops is mitigated for common refcount operations.

     With these performance improvements the generic implementation of
     refcount_t should be good enough for everybody - and this got
     confirmed by performance testing, so remove ARCH_HAS_REFCOUNT and
     REFCOUNT_FULL entirely, leaving the generic implementation enabled
     unconditionally. (Will Deacon)

   - Other misc changes, fixes, cleanups"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  lkdtm: Remove references to CONFIG_REFCOUNT_FULL
  locking/refcount: Remove unused 'refcount_error_report()' function
  locking/refcount: Consolidate implementations of refcount_t
  locking/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions
  locking/refcount: Move saturation warnings out of line
  locking/refcount: Improve performance of generic REFCOUNT_FULL code
  locking/refcount: Move the bulk of the REFCOUNT_FULL implementation into the  header
  locking/refcount: Remove unused refcount_*_checked() variants
  locking/refcount: Ensure integer operands are treated as signed
  locking/refcount: Define constants for saturation and max refcount values
  futex: Prevent exit livelock
  futex: Provide distinct return value when owner is exiting
  futex: Add mutex around futex exit
  futex: Provide state handling for exec() as well
  futex: Sanitize exit state handling
  futex: Mark the begin of futex exit explicitly
  futex: Set task::futex_state to DEAD right after handling futex exit
  futex: Split futex_mm_release() for exit/exec
  exit/exec: Seperate mm_release()
  futex: Replace PF_EXITPIDONE with a state
  ...

rcu: Upgrade rcu_swap_protected() to rcu_replace_pointer()

2019-10-30T15:43:08+00:00

Although the rcu_swap_protected() macro follows the example of
swap(), the interactions with RCU make its update of its argument
somewhat counter-intuitive.  This commit therefore introduces
an rcu_replace_pointer() that returns the old value of the RCU
pointer instead of doing the argument update.  Once all the uses of
rcu_swap_protected() are updated to instead use rcu_replace_pointer(),
rcu_swap_protected() will be removed.

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds 
[ paulmck: From rcu_replace() to rcu_replace_pointer() per Ingo Molnar. ]
Signed-off-by: Paul E. McKenney 
Cc: Bart Van Assche 
Cc: Christoph Hellwig 
Cc: Hannes Reinecke 
Cc: Johannes Thumshirn 
Cc: Shane M Seymour 
Cc: Martin K. Petersen