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Commit c52478f4 authored by Yuyang Du's avatar Yuyang Du Committed by Ingo Molnar
Browse files

locking/lockdep: Adjust lock usage bit character checks 



The lock usage bit characters are defined and determined with tricks.
Add some explanation to make it a bit clearer, then adjust the logic to
check the usage, which optimizes the code a bit.

No functional change.

Signed-off-by: default avatarYuyang Du <duyuyang@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-4-duyuyang@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c01fbbc8

kernel/locking/lockdep.c

+16 −5
Original line number Diff line number Diff line
@@ -500,15 +500,26 @@ static inline unsigned long lock_flag(enum lock_usage_bit bit) 


static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)

{

	/*

	 * The usage character defaults to '.' (i.e., irqs disabled and not in

	 * irq context), which is the safest usage category.

	 */

	char c = '.';



	if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK))

	/*

	 * The order of the following usage checks matters, which will

	 * result in the outcome character as follows:

	 *

	 * - '+': irq is enabled and not in irq context

	 * - '-': in irq context and irq is disabled

	 * - '?': in irq context and irq is enabled

	 */

	if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {

		c = '+';

	if (class->usage_mask & lock_flag(bit)) {

		c = '-';

		if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK))

		if (class->usage_mask & lock_flag(bit))

			c = '?';

	}

	} else if (class->usage_mask & lock_flag(bit))

		c = '-';



	return c;

}