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Subject[PATCH 2/2] locking/lockdep: Provide enum lock_usage_bit mask names
Date
It makes the code more self-explanatory and tells throughout the code
what magic number refers to:

* state (Hardirq/Softirq)
* direction (used in or enabled above state)
* read or write

We can even remove some comments that were compensating for the lack of
those constant names.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/lockdep.c | 33 +++++++++++----------------------
kernel/locking/lockdep_internals.h | 4 ++++
2 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 118a554..115d43e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1624,29 +1624,18 @@ static const char *state_rnames[] = {

static inline const char *state_name(enum lock_usage_bit bit)
{
- return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
+ return (bit & LOCK_USAGE_READ_MASK) ? state_rnames[bit >> 2] : state_names[bit >> 2];
}

static int exclusive_bit(int new_bit)
{
- /*
- * USED_IN
- * USED_IN_READ
- * ENABLED
- * ENABLED_READ
- *
- * bit 0 - write/read
- * bit 1 - used_in/enabled
- * bit 2+ state
- */
-
- int state = new_bit & ~3;
- int dir = new_bit & 2;
+ int state = new_bit & LOCK_USAGE_STATE_MASK;
+ int dir = new_bit & LOCK_USAGE_DIR_MASK;

/*
* keep state, bit flip the direction and strip read.
*/
- return state | (dir ^ 2);
+ return state | (dir ^ LOCK_USAGE_DIR_MASK);
}

static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
@@ -2662,8 +2651,8 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit new_bit)
{
int excl_bit = exclusive_bit(new_bit);
- int read = new_bit & 1;
- int dir = new_bit & 2;
+ int read = new_bit & LOCK_USAGE_READ_MASK;
+ int dir = new_bit & LOCK_USAGE_DIR_MASK;

/*
* mark USED_IN has to look forwards -- to ensure no dependency
@@ -2687,19 +2676,19 @@ mark_lock_irq(struct task_struct *curr, struct held_lock *this,
* states.
*/
if ((!read || !dir || STRICT_READ_CHECKS) &&
- !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
+ !usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
return 0;

/*
* Check for read in write conflicts
*/
if (!read) {
- if (!valid_state(curr, this, new_bit, excl_bit + 1))
+ if (!valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK))
return 0;

if (STRICT_READ_CHECKS &&
- !usage(curr, this, excl_bit + 1,
- state_name(new_bit + 1)))
+ !usage(curr, this, excl_bit + LOCK_USAGE_READ_MASK,
+ state_name(new_bit + LOCK_USAGE_READ_MASK)))
return 0;
}

@@ -2723,7 +2712,7 @@ mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
hlock = curr->held_locks + i;

if (hlock->read)
- hlock_bit += 1; /* READ */
+ hlock_bit += LOCK_USAGE_READ_MASK;

BUG_ON(hlock_bit >= LOCK_USAGE_STATES);

diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 88c847a..2ebb9d0 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -22,6 +22,10 @@ enum lock_usage_bit {
LOCK_USAGE_STATES
};

+#define LOCK_USAGE_READ_MASK 1
+#define LOCK_USAGE_DIR_MASK 2
+#define LOCK_USAGE_STATE_MASK (~(LOCK_USAGE_READ_MASK | LOCK_USAGE_DIR_MASK))
+
/*
* Usage-state bitmasks:
*/
--
2.7.4
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