linux.git/Documentation/RCU/Design, branch v5.10

doc: Drop doubled words from RCU requirements documentation

2020-08-24T21:29:17+00:00

Drop the doubled words "to" and "for".

Signed-off-by: Randy Dunlap 
Cc: Jonathan Corbet 
Cc: linux-doc@vger.kernel.org
Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Joel Fernandes 
Cc: rcu@vger.kernel.org
Signed-off-by: Paul E. McKenney

doc: Drop doubled words from RCU Data-Structures.rst

2020-08-24T21:29:17+00:00

Drop the doubled word "the".

Signed-off-by: Randy Dunlap 
Cc: Jonathan Corbet 
Cc: linux-doc@vger.kernel.org
Cc: "Paul E. McKenney" 
Cc: Josh Triplett 
Cc: Steven Rostedt 
Cc: Mathieu Desnoyers 
Cc: Lai Jiangshan 
Cc: Joel Fernandes 
Cc: rcu@vger.kernel.org
Signed-off-by: Paul E. McKenney

Merge tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-03T21:31:33+00:00

Pull RCU updates from Ingo Molnar:

 - kfree_rcu updates

 - RCU tasks updates

 - Read-side scalability tests

 - SRCU updates

 - Torture-test updates

 - Documentation updates

 - Miscellaneous fixes

* tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (109 commits)
  torture: Remove obsolete "cd $KVM"
  torture: Avoid duplicate specification of qemu command
  torture: Dump ftrace at shutdown only if requested
  torture: Add kvm-tranform.sh script for qemu-cmd files
  torture: Add more tracing crib notes to kvm.sh
  torture: Improve diagnostic for KCSAN-incapable compilers
  torture: Correctly summarize build-only runs
  torture: Pass --kmake-arg to all make invocations
  rcutorture: Check for unwatched readers
  torture: Abstract out console-log error detection
  torture: Add a stop-run capability
  torture: Create qemu-cmd in --buildonly runs
  rcu/rcutorture: Replace 0 with false
  torture: Add --allcpus argument to the kvm.sh script
  torture: Remove whitespace from identify_qemu_vcpus output
  rcutorture: NULL rcu_torture_current earlier in cleanup code
  rcutorture: Handle non-statistic bang-string error messages
  torture: Set configfile variable to current scenario
  rcutorture: Add races with task-exit processing
  locktorture: Use true and false to assign to bool variables
  ...

Documentation/barriers: Remove references to [smp_]read_barrier_depends()

2020-07-21T09:50:36+00:00

The [smp_]read_barrier_depends() barrier macros no longer exist as
part of the Linux memory model, so remove all references to them from
the Documentation/ directory.

Although this is fairly mechanical on the whole, we drop the "CACHE
COHERENCY" section entirely from 'memory-barriers.txt' as it doesn't
make any sense now that the dependency barriers have been removed.

Acked-by: Peter Zijlstra (Intel) 
Acked-by: Paul E. McKenney 
Signed-off-by: Will Deacon

doc: Tasks RCU must protect instructions before trampoline

2020-06-29T18:58:11+00:00

Protecting the code in a trampoline can also require protecting a
number of instructions prior to actually entering the trampoline.
For example, these earlier instructions might be computing the address
of the trampoline.  This commit therefore updates RCU's requirements to
record this for posterity.

Link: https://lore.kernel.org/lkml/20200511154824.09a18c46@gandalf.local.home/
Reported-by: Lai Jiangshan 
Reported-by: Steven Rostedt 
Signed-off-by: Paul E. McKenney

rcu: Make rcu_read_unlock_special() safe for rq/pi locks

2020-04-27T18:03:50+00:00

The scheduler is currently required to hold rq/pi locks across the entire
RCU read-side critical section or not at all.  This is inconvenient and
leaves traps for the unwary, including the author of this commit.

But now that excessively long grace periods enable scheduling-clock
interrupts for holdout nohz_full CPUs, the nohz_full rescue logic in
rcu_read_unlock_special() can be dispensed with.  In other words, the
rcu_read_unlock_special() function can refrain from doing wakeups unless
such wakeups are guaranteed safe.

This commit therefore avoids unsafe wakeups, freeing the scheduler to
hold rq/pi locks across rcu_read_unlock() even if the corresponding RCU
read-side critical section might have been preempted.  This commit also
updates RCU's requirements documentation.

This commit is inspired by a patch from Lai Jiangshan:
https://lore.kernel.org/lkml/20191102124559.1135-2-laijs@linux.alibaba.com
This commit is further intended to be a step towards his goal of permitting
the inlining of RCU-preempt's rcu_read_lock() and rcu_read_unlock().

Cc: Lai Jiangshan 
Signed-off-by: Paul E. McKenney

doc/RCU/Design: Remove remaining HTML tags in ReST files

2020-02-27T15:03:13+00:00

Commit ccc9971e2147 ("docs: rcu: convert some articles from html to
ReST") has converted a few of html RCU docs into ReST files, but a few
of html tags which not supported on rst is remaining.  This commit
converts those to ReST appropriate alternatives.

Reviewed-by: Madhuparna Bhowmik 
Signed-off-by: SeongJae Park 
Signed-off-by: Paul E. McKenney

Documentation: Rename rcu_node_context_switch() to rcu_note_context_switch()

2019-10-29T09:48:29+00:00

While Paul was explaining some RCU magic I noticed a typo in
rcu_note_context_switch().  As a result, this commit replaces
rcu_node_context_switch() with rcu_note_context_switch().

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Paul E. McKenney

Restore docs "rcu: Restore barrier() to rcu_read_lock() and rcu_read_unlock()"

2019-10-29T09:48:23+00:00

This restores docs back in ReST format.

Signed-off-by: Joel Fernandes (Google) 
[ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ]
[ paulmck: Joel approved via private email. ]
Signed-off-by: Paul E. McKenney

Restore docs "treewide: Rename rcu_dereference_raw_notrace() to _check()"

2019-10-29T09:48:14+00:00

This restores docs back in ReST format.

Signed-off-by: Joel Fernandes (Google) 
[ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ]
[ paulmck: Joel approved via private email. ]
Signed-off-by: Paul E. McKenney