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Subject[PATCH 1/3] lockdep: Use enum type on hlock->read instead of magic number
Date
Currently hlock->read can have the following values:

0: write type
1: read type
2: read recursion type

It would be better to use human readable type than magic numbers.
Furthermore, this way it's easier to extend it so that hlock->read
has another value.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/locking/lockdep.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 44c8d0d..0ac2f70 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -76,6 +76,14 @@
#define lock_stat 0
#endif

+#define LT_WRITE 0 /* 0: write type */
+#define LT_READ_N 1 /* 1: read non-recursion type */
+#define LT_READ_R 2 /* 2: read recursion type */
+
+#define is_write(a) ((a) == LT_WRITE)
+#define is_read(a) ((a) == LT_READ_N || (a) == LT_READ_R)
+#define is_read_r(a) ((a) == LT_READ_R)
+
/*
* lockdep_lock: protects the lockdep graph, the hashes and the
* class/list/hash allocators.
@@ -271,9 +279,9 @@ static void lock_release_holdtime(struct held_lock *hlock)
holdtime = lockstat_clock() - hlock->holdtime_stamp;

stats = get_lock_stats(hlock_class(hlock));
- if (hlock->read)
+ if (is_read(hlock->read))
lock_time_inc(&stats->read_holdtime, holdtime);
- else
+ else if (is_write(hlock->read))
lock_time_inc(&stats->write_holdtime, holdtime);
put_lock_stats(stats);
}
@@ -1828,7 +1836,7 @@ static inline void inc_chains(void)
* Allow read-after-read recursion of the same
* lock class (i.e. read_lock(lock)+read_lock(lock)):
*/
- if ((read == 2) && prev->read)
+ if (is_read_r(read) && is_read(prev->read))
return 2;

/*
@@ -1906,7 +1914,7 @@ static inline void inc_chains(void)
* write-lock never takes any other locks, then the reads are
* equivalent to a NOP.
*/
- if (next->read == 2 || prev->read == 2)
+ if (is_read_r(next->read) || is_read_r(prev->read))
return 1;
/*
* Is the <prev> -> <next> dependency already present?
@@ -2016,7 +2024,7 @@ static inline void inc_chains(void)
* Only non-recursive-read entries get new dependencies
* added:
*/
- if (hlock->read != 2 && hlock->check) {
+ if (!is_read_r(hlock->read) && hlock->check) {
int ret = check_prev_add(curr, hlock, next,
distance, &trace, save);
if (!ret)
@@ -2460,7 +2468,7 @@ static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
* trylock entries):
*/
if (ret == 2)
- hlock->read = 2;
+ hlock->read = LT_READ_R;
/*
* Add dependency only if this lock is not the head
* of the chain, and if it's not a secondary read-lock:
@@ -2848,7 +2856,7 @@ enum mark_type {
hlock = curr->held_locks + i;

usage_bit = 2 + (mark << 2); /* ENABLED */
- if (hlock->read)
+ if (is_read(hlock->read))
usage_bit += 1; /* READ */

BUG_ON(usage_bit >= LOCK_USAGE_STATES);
@@ -3060,7 +3068,7 @@ static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
* mark the lock as used in these contexts:
*/
if (!hlock->trylock) {
- if (hlock->read) {
+ if (is_read(hlock->read)) {
if (curr->hardirq_context)
if (!mark_lock(curr, hlock,
LOCK_USED_IN_HARDIRQ_READ))
@@ -3079,7 +3087,7 @@ static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
}
}
if (!hlock->hardirqs_off) {
- if (hlock->read) {
+ if (is_read(hlock->read)) {
if (!mark_lock(curr, hlock,
LOCK_ENABLED_HARDIRQ_READ))
return 0;
@@ -3715,7 +3723,7 @@ static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
curr->curr_chain_key = hlock->prev_chain_key;

WARN(hlock->read, "downgrading a read lock");
- hlock->read = 1;
+ hlock->read = LT_READ_N;
hlock->acquire_ip = ip;

if (reacquire_held_locks(curr, depth, i))
@@ -4167,7 +4175,7 @@ void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
if (contending_point < LOCKSTAT_POINTS)
stats->contending_point[contending_point]++;
if (lock->cpu != smp_processor_id())
- stats->bounces[bounce_contended + !!hlock->read]++;
+ stats->bounces[bounce_contended + is_read(hlock->read)]++;
put_lock_stats(stats);
}

@@ -4209,13 +4217,13 @@ void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)

stats = get_lock_stats(hlock_class(hlock));
if (waittime) {
- if (hlock->read)
+ if (is_read(hlock->read))
lock_time_inc(&stats->read_waittime, waittime);
- else
+ else if (is_write(hlock->read))
lock_time_inc(&stats->write_waittime, waittime);
}
if (lock->cpu != cpu)
- stats->bounces[bounce_acquired + !!hlock->read]++;
+ stats->bounces[bounce_acquired + is_read(hlock->read)]++;
put_lock_stats(stats);

lock->cpu = cpu;
@@ -4819,7 +4827,7 @@ static inline struct lock_class *xlock_class(struct cross_lock *xlock)
*/
static inline int depend_before(struct held_lock *hlock)
{
- return hlock->read != 2 && hlock->check && !hlock->trylock;
+ return !is_read_r(hlock->read) && hlock->check && !hlock->trylock;
}

/*
@@ -4827,7 +4835,7 @@ static inline int depend_before(struct held_lock *hlock)
*/
static inline int depend_after(struct held_lock *hlock)
{
- return hlock->read != 2 && hlock->check;
+ return !is_read_r(hlock->read) && hlock->check;
}

/*
--
1.9.1
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