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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: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yuyang Du 2019-05-06 16:19:19 +08:00 committed by Ingo Molnar
parent c01fbbc83f
commit c52478f4f3
1 changed files with 16 additions and 5 deletions
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21
kernel/locking/lockdep.c
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@ -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;
}