linux-toradex.git/kernel/locking/lockdep.c, branch v5.3-rc6

locking/lockdep: Clean up #ifdef checks

2019-07-25T13:39:26+00:00

As Will Deacon points out, CONFIG_PROVE_LOCKING implies TRACE_IRQFLAGS,
so the conditions I added in the previous patch, and some others in the
same file can be simplified by only checking for the former.

No functional change.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Will Deacon 
Cc: Andrew Morton 
Cc: Bart Van Assche 
Cc: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: Yuyang Du 
Fixes: 886532aee3cd ("locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING")
Link: https://lkml.kernel.org/r/20190628102919.2345242-1-arnd@arndb.de
Signed-off-by: Ingo Molnar

locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING

2019-06-25T08:17:07+00:00

The last cleanup patch triggered another issue, as now another function
should be moved into the same section:

 kernel/locking/lockdep.c:3580:12: error: 'mark_lock' defined but not used [-Werror=unused-function]
  static int mark_lock(struct task_struct *curr, struct held_lock *this,

Move mark_lock() into the same #ifdef section as its only caller, and
remove the now-unused mark_lock_irq() stub helper.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Bart Van Assche 
Cc: Frederic Weisbecker 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Waiman Long 
Cc: Will Deacon 
Cc: Yuyang Du 
Fixes: 0d2cc3b34532 ("locking/lockdep: Move valid_state() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING")
Link: https://lkml.kernel.org/r/20190617124718.1232976-1-arnd@arndb.de
Signed-off-by: Ingo Molnar

locking/lockdep: Remove unnecessary DEBUG_LOCKS_WARN_ON()

2019-06-17T10:09:37+00:00

DEBUG_LOCKS_WARN_ON() will turn off debug_locks and
makes print_unlock_imbalance_bug() return directly.

Remove a redundant whitespace.

Signed-off-by: Kobe Wu 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: 
Cc: 
Cc: Eason Lin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: https://lkml.kernel.org/r/1559217575-30298-1-git-send-email-kobe-cp.wu@mediatek.com
Signed-off-by: Ingo Molnar

locking/lockdep: Fix merging of hlocks with non-zero references

2019-06-03T10:32:56+00:00

The sequence

	static DEFINE_WW_CLASS(test_ww_class);

	struct ww_acquire_ctx ww_ctx;
	struct ww_mutex ww_lock_a;
	struct ww_mutex ww_lock_b;
	struct ww_mutex ww_lock_c;
	struct mutex lock_c;

	ww_acquire_init(&ww_ctx, &test_ww_class);

	ww_mutex_init(&ww_lock_a, &test_ww_class);
	ww_mutex_init(&ww_lock_b, &test_ww_class);
	ww_mutex_init(&ww_lock_c, &test_ww_class);

	mutex_init(&lock_c);

	ww_mutex_lock(&ww_lock_a, &ww_ctx);

	mutex_lock(&lock_c);

	ww_mutex_lock(&ww_lock_b, &ww_ctx);
	ww_mutex_lock(&ww_lock_c, &ww_ctx);

	mutex_unlock(&lock_c);	(*)

	ww_mutex_unlock(&ww_lock_c);
	ww_mutex_unlock(&ww_lock_b);
	ww_mutex_unlock(&ww_lock_a);

	ww_acquire_fini(&ww_ctx); (**)

will trigger the following error in __lock_release() when calling
mutex_release() at **:

	DEBUG_LOCKS_WARN_ON(depth <= 0)

The problem is that the hlock merging happening at * updates the
references for test_ww_class incorrectly to 3 whereas it should've
updated it to 4 (representing all the instances for ww_ctx and
ww_lock_[abc]).

Fix this by updating the references during merging correctly taking into
account that we can have non-zero references (both for the hlock that we
merge into another hlock or for the hlock we are merging into).

Signed-off-by: Imre Deak 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Link: https://lkml.kernel.org/r/20190524201509.9199-2-imre.deak@intel.com
Signed-off-by: Ingo Molnar

locking/lockdep: Fix OOO unlock when hlocks need merging

2019-06-03T10:32:29+00:00

The sequence

	static DEFINE_WW_CLASS(test_ww_class);

	struct ww_acquire_ctx ww_ctx;
	struct ww_mutex ww_lock_a;
	struct ww_mutex ww_lock_b;
	struct mutex lock_c;
	struct mutex lock_d;

	ww_acquire_init(&ww_ctx, &test_ww_class);

	ww_mutex_init(&ww_lock_a, &test_ww_class);
	ww_mutex_init(&ww_lock_b, &test_ww_class);

	mutex_init(&lock_c);

	ww_mutex_lock(&ww_lock_a, &ww_ctx);

	mutex_lock(&lock_c);

	ww_mutex_lock(&ww_lock_b, &ww_ctx);

	mutex_unlock(&lock_c);		(*)

	ww_mutex_unlock(&ww_lock_b);
	ww_mutex_unlock(&ww_lock_a);

	ww_acquire_fini(&ww_ctx);

triggers the following WARN in __lock_release() when doing the unlock at *:

	DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1);

The problem is that the WARN check doesn't take into account the merging
of ww_lock_a and ww_lock_b which results in decreasing curr->lockdep_depth
by 2 not only 1.

Note that the following sequence doesn't trigger the WARN, since there
won't be any hlock merging.

	ww_acquire_init(&ww_ctx, &test_ww_class);

	ww_mutex_init(&ww_lock_a, &test_ww_class);
	ww_mutex_init(&ww_lock_b, &test_ww_class);

	mutex_init(&lock_c);
	mutex_init(&lock_d);

	ww_mutex_lock(&ww_lock_a, &ww_ctx);

	mutex_lock(&lock_c);
	mutex_lock(&lock_d);

	ww_mutex_lock(&ww_lock_b, &ww_ctx);

	mutex_unlock(&lock_d);

	ww_mutex_unlock(&ww_lock_b);
	ww_mutex_unlock(&ww_lock_a);

	mutex_unlock(&lock_c);

	ww_acquire_fini(&ww_ctx);

In general both of the above two sequences are valid and shouldn't
trigger any lockdep warning.

Fix this by taking the decrement due to the hlock merging into account
during lock release and hlock class re-setting. Merging can't happen
during lock downgrading since there won't be a new possibility to merge
hlocks in that case, so add a WARN if merging still happens then.

Signed-off-by: Imre Deak 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Cc: ville.syrjala@linux.intel.com
Link: https://lkml.kernel.org/r/20190524201509.9199-1-imre.deak@intel.com
Signed-off-by: Ingo Molnar

locking/lockdep: Remove !dir in lock irq usage check

2019-06-03T09:55:53+00:00

In mark_lock_irq(), the following checks are performed:

   ----------------------------------
  |   ->      | unsafe | read unsafe |
  |----------------------------------|
  | safe      |  F  B  |    F* B*    |
  |----------------------------------|
  | read safe |  F? B* |      -      |
   ----------------------------------

Where:
F: check_usage_forwards
B: check_usage_backwards
*: check enabled by STRICT_READ_CHECKS
?: check enabled by the !dir condition

From checking point of view, the special F? case does not make sense,
whereas it perhaps is made for peroformance concern. As later patch will
address this issue, remove this exception, which makes the checks
consistent later.

With STRICT_READ_CHECKS = 1 which is default, there is no functional
change.

Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-24-duyuyang@gmail.com
Signed-off-by: Ingo Molnar

locking/lockdep: Adjust new bit cases in mark_lock

2019-06-03T09:55:52+00:00

The new bit can be any possible lock usage except it is garbage, so the
cases in switch can be made simpler. Warn early on if wrong usage bit is
passed without taking locks. No functional change.

Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-23-duyuyang@gmail.com
Signed-off-by: Ingo Molnar

locking/lockdep: Consolidate lock usage bit initialization

2019-06-03T09:55:51+00:00

Lock usage bit initialization is consolidated into one function
mark_usage(). Trivial readability improvement. No functional change.

Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-22-duyuyang@gmail.com
Signed-off-by: Ingo Molnar

locking/lockdep: Check redundant dependency only when CONFIG_LOCKDEP_SMALL

2019-06-03T09:55:50+00:00

As Peter has put it all sound and complete for the cause, I simply quote:

"It (check_redundant) was added for cross-release (which has since been
reverted) which would generate a lot of redundant links (IIRC) but
having it makes the reports more convoluted -- basically, if we had an
A-B-C relation, then A-C will not be added to the graph because it is
already covered. This then means any report will include B, even though
a shorter cycle might have been possible."

This would increase the number of direct dependencies. For a simple workload
(make clean; reboot; make vmlinux -j8), the data looks like this:

 CONFIG_LOCKDEP_SMALL: direct dependencies:                  6926

!CONFIG_LOCKDEP_SMALL: direct dependencies:                  9052    (+30.7%)

Suggested-by: Peter Zijlstra (Intel) 
Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-21-duyuyang@gmail.com
Signed-off-by: Ingo Molnar

locking/lockdep: Refactorize check_noncircular and check_redundant

2019-06-03T09:55:50+00:00

These two functions now handle different check results themselves. A new
check_path function is added to check whether there is a path in the
dependency graph. No functional change.

Signed-off-by: Yuyang Du 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-20-duyuyang@gmail.com
Signed-off-by: Ingo Molnar