linux-stable.git/kernel/locking/lockdep.c, branch v5.0.6

locking/lockdep: Add debug_locks check in __lock_downgrade()

2019-03-27T05:18:00+00:00

commit 71492580571467fb7177aade19c18ce7486267f5 upstream.

Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
warning right after a previous lockdep warning. It is likely that the
previous warning turned off lock debugging causing the lockdep to have
inconsistency states leading to the lock downgrade warning.

Fix that by add a check for debug_locks at the beginning of
__lock_downgrade().

Debugged-by: Tetsuo Handa 
Reported-by: Tetsuo Handa 
Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com
Signed-off-by: Waiman Long 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

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

2018-12-26T22:25:52+00:00

Pull locking updates from Ingo Molnar:
 "The main change in this cycle are initial preparatory bits of dynamic
  lockdep keys support from Bart Van Assche.

  There are also misc changes, a comment cleanup and a data structure
  cleanup"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Clean up comment in nohz_idle_balance()
  locking/lockdep: Stop using RCU primitives to access 'all_lock_classes'
  locking/lockdep: Make concurrent lockdep_reset_lock() calls safe
  locking/lockdep: Remove a superfluous INIT_LIST_HEAD() statement
  locking/lockdep: Introduce lock_class_cache_is_registered()
  locking/lockdep: Inline __lockdep_init_map()
  locking/lockdep: Declare local symbols static
  tools/lib/lockdep/tests: Test the lockdep_reset_lock() implementation
  tools/lib/lockdep: Add dummy print_irqtrace_events() implementation
  tools/lib/lockdep: Rename "trywlock" into "trywrlock"
  tools/lib/lockdep/tests: Run lockdep tests a second time under Valgrind
  tools/lib/lockdep/tests: Improve testing accuracy
  tools/lib/lockdep/tests: Fix shellcheck warnings
  tools/lib/lockdep/tests: Display compiler warning and error messages
  locking/lockdep: Remove ::version from lock_class structure

locking/lockdep: Stop using RCU primitives to access 'all_lock_classes'

2018-12-11T13:54:56+00:00

Due to the previous patch all code that accesses the 'all_lock_classes'
list holds the graph lock. Hence use regular list primitives instead of
their RCU variants to access this list.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-14-bvanassche@acm.org
Signed-off-by: Ingo Molnar

locking/lockdep: Make concurrent lockdep_reset_lock() calls safe

2018-12-11T13:54:55+00:00

Since zap_class() removes items from the all_lock_classes list and the
classhash_table, protect all zap_class() calls against concurrent
data structure modifications with the graph lock.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-13-bvanassche@acm.org
Signed-off-by: Ingo Molnar

locking/lockdep: Remove a superfluous INIT_LIST_HEAD() statement

2018-12-11T13:54:54+00:00

Initializing a list entry just before it is passed to list_add_tail_rcu()
is not necessary because list_add_tail_rcu() overwrites the next and prev
pointers anyway. Hence remove the INIT_LIST_HEAD() statement.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-12-bvanassche@acm.org
Signed-off-by: Ingo Molnar

locking/lockdep: Introduce lock_class_cache_is_registered()

2018-12-11T13:54:53+00:00

This patch does not change any functionality but makes the
lockdep_reset_lock() function easier to read.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-11-bvanassche@acm.org
Signed-off-by: Ingo Molnar

locking/lockdep: Inline __lockdep_init_map()

2018-12-11T13:54:51+00:00

Since the function __lockdep_init_map() only has one caller, inline it
into its caller. This patch does not change any functionality.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-10-bvanassche@acm.org
Signed-off-by: Ingo Molnar

locking/lockdep: Declare local symbols static

2018-12-11T13:54:51+00:00

This patch avoids that sparse complains about a missing declaration for
the lock_classes array when building with CONFIG_DEBUG_LOCKDEP=n.

Signed-off-by: Bart Van Assche 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Johannes Berg 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20181207011148.251812-9-bvanassche@acm.org
Signed-off-by: Ingo Molnar

lockdep: Replace synchronize_sched() with synchronize_rcu()

2018-11-27T17:21:42+00:00

Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu().  This commit therefore makes this change.

Signed-off-by: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Will Deacon

locking/lockdep: Fix debug_locks off performance problem

2018-10-19T05:53:17+00:00

It was found that when debug_locks was turned off because of a problem
found by the lockdep code, the system performance could drop quite
significantly when the lock_stat code was also configured into the
kernel. For instance, parallel kernel build time on a 4-socket x86-64
server nearly doubled.

Further analysis into the cause of the slowdown traced back to the
frequent call to debug_locks_off() from the __lock_acquired() function
probably due to some inconsistent lockdep states with debug_locks
off. The debug_locks_off() function did an unconditional atomic xchg
to write a 0 value into debug_locks which had already been set to 0.
This led to severe cacheline contention in the cacheline that held
debug_locks.  As debug_locks is being referenced in quite a few different
places in the kernel, this greatly slow down the system performance.

To prevent that trashing of debug_locks cacheline, lock_acquired()
and lock_contended() now checks the state of debug_locks before
proceeding. The debug_locks_off() function is also modified to check
debug_locks before calling __debug_locks_off().

Signed-off-by: Waiman Long 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: http://lkml.kernel.org/r/1539913518-15598-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar