linux-toradex.git/kernel/locking, branch v5.19-rc8

locking/lockdep: Use sched_clock() for random numbers

2022-06-13T08:29:57+00:00

Since the rewrote of prandom_u32(), in the commit mentioned below, the
function uses sleeping locks which extracing random numbers and filling
the batch.
This breaks lockdep on PREEMPT_RT because lock_pin_lock() disables
interrupts while calling __lock_pin_lock(). This can't be moved earlier
because the main user of the function (rq_pin_lock()) invokes that
function after disabling interrupts in order to acquire the lock.

The cookie does not require random numbers as its goal is to provide a
random value in order to notice unexpected "unlock + lock" sites.

Use sched_clock() to provide random numbers.

Fixes: a0103f4d86f88 ("random32: use real rng for non-deterministic randomness")
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/YoNn3pTkm5+QzE5k@linutronix.de

Merge tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

2022-05-26T23:57:20+00:00

Pull sysctl updates from Luis Chamberlain:
 "For two kernel releases now kernel/sysctl.c has been being cleaned up
  slowly, since the tables were grossly long, sprinkled with tons of
  #ifdefs and all this caused merge conflicts with one susbystem or
  another.

  This tree was put together to help try to avoid conflicts with these
  cleanups going on different trees at time. So nothing exciting on this
  pull request, just cleanups.

  Thanks a lot to the Uniontech and Huawei folks for doing some of this
  nasty work"

* tag 'sysctl-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: (28 commits)
  sched: Fix build warning without CONFIG_SYSCTL
  reboot: Fix build warning without CONFIG_SYSCTL
  kernel/kexec_core: move kexec_core sysctls into its own file
  sysctl: minor cleanup in new_dir()
  ftrace: fix building with SYSCTL=y but DYNAMIC_FTRACE=n
  fs/proc: Introduce list_for_each_table_entry for proc sysctl
  mm: fix unused variable kernel warning when SYSCTL=n
  latencytop: move sysctl to its own file
  ftrace: fix building with SYSCTL=n but DYNAMIC_FTRACE=y
  ftrace: Fix build warning
  ftrace: move sysctl_ftrace_enabled to ftrace.c
  kernel/do_mount_initrd: move real_root_dev sysctls to its own file
  kernel/delayacct: move delayacct sysctls to its own file
  kernel/acct: move acct sysctls to its own file
  kernel/panic: move panic sysctls to its own file
  kernel/lockdep: move lockdep sysctls to its own file
  mm: move page-writeback sysctls to their own file
  mm: move oom_kill sysctls to their own file
  kernel/reboot: move reboot sysctls to its own file
  sched: Move energy_aware sysctls to topology.c
  ...

locking/qrwlock: Change "queue rwlock" to "queued rwlock"

2022-05-11T14:27:04+00:00

Queued rwlock was originally named "queue rwlock" which wasn't quite
grammatically correct. However there are still some "queue rwlock"
references in the code. Change those to "queued rwlock" for consistency.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220510192134.434753-1-longman@redhat.com

kernel/lockdep: move lockdep sysctls to its own file

2022-04-06T20:43:44+00:00

kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

All filesystem syctls now get reviewed by fs folks. This commit
follows the commit of fs, move the prove_locking and lock_stat sysctls
to its own file, kernel/lockdep.c.

Signed-off-by: tangmeng 
Signed-off-by: Luis Chamberlain

locking/mutex: Make contention tracepoints more consistent wrt adaptive spinning

2022-04-05T08:24:36+00:00

Have the trace_contention_*() tracepoints consistently include
adaptive spinning. In order to differentiate between the spinning and
non-spinning states add LCB_F_MUTEX and combine with LCB_F_SPIN.

The consequence is that a mutex contention can now triggler multiple
_begin() tracepoints before triggering an _end().

Additionally, this fixes one path where mutex would trigger _end()
without ever seeing a _begin().

Signed-off-by: Peter Zijlstra (Intel)

locking: Apply contention tracepoints in the slow path

2022-04-05T08:24:35+00:00

Adding the lock contention tracepoints in various lock function slow
paths.  Note that each arch can define spinlock differently, I only
added it only to the generic qspinlock for now.

Signed-off-by: Namhyung Kim 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Link: https://lkml.kernel.org/r/20220322185709.141236-3-namhyung@kernel.org

locking: Add lock contention tracepoints

2022-04-05T08:24:35+00:00

This adds two new lock contention tracepoints like below:

 * lock:contention_begin
 * lock:contention_end

The lock:contention_begin takes a flags argument to classify locks.  I
found it useful to identify what kind of locks it's tracing like if
it's spinning or sleeping, reader-writer lock, real-time, and per-cpu.

Move tracepoint definitions into mutex.c so that we can use them
without lockdep.

Signed-off-by: Namhyung Kim 
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Link: https://lkml.kernel.org/r/20220322185709.141236-2-namhyung@kernel.org

locking/rwsem: Always try to wake waiters in out_nolock path

2022-04-05T08:24:35+00:00

For writers, the out_nolock path will always attempt to wake up waiters.
This may not be really necessary if the waiter to be removed is not the
first one.

For readers, no attempt to wake up waiter is being made. However, if
the HANDOFF bit is set and the reader to be removed is the first waiter,
the waiter behind it will inherit the HANDOFF bit and for a write lock
waiter waking it up will allow it to spin on the lock to acquire it
faster. So it can be beneficial to do a wakeup in this case.

Add a new rwsem_del_wake_waiter() helper function to do that consistently
for both reader and writer out_nolock paths.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220322152059.2182333-4-longman@redhat.com

locking/rwsem: Conditionally wake waiters in reader/writer slowpaths

2022-04-05T08:24:35+00:00

In an analysis of a recent vmcore, a reader-owned rwsem was found with
385 readers but no writer in the wait queue. That is kind of unusual
but it may be caused by some race conditions that we have not fully
understood yet. In such a case, all the readers in the wait queue should
join the other reader-owners and acquire the read lock.

In rwsem_down_write_slowpath(), an incoming writer will try to
wake up the front readers under such circumstance. That is not
the case for rwsem_down_read_slowpath(), add a new helper function
rwsem_cond_wake_waiter() to do wakeup and use it in both reader and
writer slowpaths to have a consistent and correct behavior.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220322152059.2182333-3-longman@redhat.com

locking/rwsem: No need to check for handoff bit if wait queue empty

2022-04-05T08:24:34+00:00

Since commit d257cc8cb8d5 ("locking/rwsem: Make handoff bit handling
more consistent"), the handoff bit is always cleared if the wait queue
becomes empty. There is no need to check for RWSEM_FLAG_HANDOFF when
the wait list is known to be empty.

Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20220322152059.2182333-2-longman@redhat.com