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ck_swlock: Various improvements.

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- Remove recursive locks.
- Remove unnecessary fences.
- Add necessary fences.
- Simplify state machine.
ck_pring
Samy Al Bahra 11 years ago
parent 66aee95dd1
commit e2f7df0f1d
2 changed files with 35 additions and 211 deletions
Show Stats Download Patch File Download Diff File

159
include/ck_swlock.h
Unescape View File

@ -42,7 +42,8 @@ typedef struct ck_swlock ck_swlock_t;
#define CK_SWLOCK_INITIALIZER {0}
#define CK_SWLOCK_WRITER_BIT (1UL << 31)
#define CK_SWLOCK_LATCH_BIT (1UL << 30)
#define CK_SWLOCK_READER_BITS (UINT32_MAX ^ (CK_SWLOCK_LATCH_BIT | CK_SWLOCK_WRITER_BIT))
#define CK_SWLOCK_WRITER_MASK (CK_SWLOCK_LATCH_BIT | CK_SWLOCK_WRITER_BIT)
#define CK_SWLOCK_READER_BITS (UINT32_MAX ^ CK_SWLOCK_WRITER_MASK)
CK_CC_INLINE static void
ck_swlock_init(struct ck_swlock *rw)
@ -93,7 +94,7 @@ ck_swlock_write_trylock(ck_swlock_t *rw)
ck_pr_or_32(&rw->value, CK_SWLOCK_WRITER_BIT);
if ((ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_BITS) != 0) {
if (ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_BITS) {
ck_swlock_write_unlock(rw);
return false;
}
@ -110,11 +111,10 @@ ck_swlock_write_lock(ck_swlock_t *rw)
{
ck_pr_or_32(&rw->value, CK_SWLOCK_WRITER_BIT);
ck_pr_fence_acquire();
while ((ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_BITS) != 0)
while (ck_pr_load_32(&rw->value) & CK_SWLOCK_READER_BITS)
ck_pr_stall();
ck_pr_fence_acquire();
return;
}
@ -122,17 +122,14 @@ CK_CC_INLINE static void
ck_swlock_write_latch(ck_swlock_t *rw)
{
ck_pr_or_32(&rw->value, CK_SWLOCK_WRITER_BIT);
ck_pr_fence_acquire();
/* Stall until readers have seen the latch and cleared. */
while (ck_pr_cas_32(&rw->value, CK_SWLOCK_WRITER_BIT,
(CK_SWLOCK_WRITER_BIT | CK_SWLOCK_LATCH_BIT)) == false) {
while (ck_pr_cas_32(&rw->value, 0, CK_SWLOCK_WRITER_MASK) == false) {
do {
ck_pr_stall();
} while (ck_pr_load_uint(&rw->value) != CK_SWLOCK_WRITER_BIT);
} while (ck_pr_load_uint(&rw->value) != 0);
}
ck_pr_fence_acquire();
return;
}
@ -169,20 +166,22 @@ CK_CC_INLINE static void
ck_swlock_read_lock(ck_swlock_t *rw)
{
uint32_t l;
for (;;) {
while (ck_pr_load_32(&rw->value) & CK_SWLOCK_WRITER_BIT)
ck_pr_stall();
l = ck_pr_faa_32(&rw->value, 1);
ck_pr_fence_acquire();
if (!(l & CK_SWLOCK_WRITER_BIT))
return;
if (l & CK_SWLOCK_WRITER_BIT) {
ck_pr_dec_32(&rw->value);
continue;
}
break;
}
ck_pr_fence_acquire();
return;
}
@ -194,39 +193,41 @@ ck_swlock_read_trylatchlock(ck_swlock_t *rw)
if (l & CK_SWLOCK_WRITER_BIT)
return false;
l = ck_pr_faa_32(&rw->value, 1);
l = ck_pr_faa_32(&rw->value, 1) & CK_SWLOCK_WRITER_MASK;
if (l == 0) {
ck_pr_fence_acquire();
if (!(l & CK_SWLOCK_WRITER_BIT))
return true;
}
if (!(l & CK_SWLOCK_LATCH_BIT))
if (l == CK_SWLOCK_WRITER_BIT)
ck_pr_dec_32(&rw->value);
return false;
}
CK_CC_INLINE static void
ck_swlock_read_latchlock(ck_swlock_t *rw)
{
uint32_t l;
for (;;) {
while (ck_pr_load_32(&rw->value) & CK_SWLOCK_WRITER_BIT)
ck_pr_stall();
l = ck_pr_faa_32(&rw->value, 1);
ck_pr_fence_acquire();
l = ck_pr_faa_32(&rw->value, 1) & CK_SWLOCK_WRITER_MASK;
if (l == 0)
break;
if (!(l & (CK_SWLOCK_LATCH_BIT | CK_SWLOCK_WRITER_BIT)))
return;
if (!(l & CK_SWLOCK_LATCH_BIT))
/*
* If the latch bit has not been sent, then the writer would
* have observed the reader and will wait to completion of
* read-side critical section.
*/
if (l == CK_SWLOCK_WRITER_BIT)
ck_pr_dec_32(&rw->value);
}
ck_pr_fence_acquire();
return;
}
@ -252,105 +253,5 @@ CK_ELIDE_PROTOTYPE(ck_swlock_read, ck_swlock_t,
ck_swlock_locked_writer, ck_swlock_read_lock,
ck_swlock_locked_reader, ck_swlock_read_unlock)
/*
* Recursive writer reader-writer lock implementation.
*/
struct ck_swlock_recursive {
struct ck_swlock rw;
uint32_t wc;
};
typedef struct ck_swlock_recursive ck_swlock_recursive_t;
#define CK_SWLOCK_RECURSIVE_INITIALIZER {CK_SWLOCK_INITIALIZER, 0}
CK_CC_INLINE static void
ck_swlock_recursive_write_lock(ck_swlock_recursive_t *rw)
{
if (++rw->wc != 1) {
return;
}
ck_swlock_write_lock(&rw->rw);
return;
}
CK_CC_INLINE static void
ck_swlock_recursive_write_latch(ck_swlock_recursive_t *rw)
{
ck_swlock_write_latch(&rw->rw);
rw->wc++;
return;
}
CK_CC_INLINE static bool
ck_swlock_recursive_write_trylock(ck_swlock_recursive_t *rw)
{
if (ck_swlock_write_trylock(&rw->rw) == true) {
rw->wc++;
return true;
}
return false;
}
CK_CC_INLINE static void
ck_swlock_recursive_write_unlock(ck_swlock_recursive_t *rw)
{
if (--rw->wc != 0)
return;
ck_swlock_write_unlock(&rw->rw);
return;
}
CK_CC_INLINE static void
ck_swlock_recursive_write_unlatch(ck_swlock_recursive_t *rw)
{
if (--rw->wc != 0) {
ck_pr_store_32(&rw->rw.value, CK_SWLOCK_WRITER_BIT);
return;
}
ck_pr_store_32(&rw->rw.value, 0);
return;
}
CK_CC_INLINE static void
ck_swlock_recursive_read_lock(ck_swlock_recursive_t *rw)
{
ck_swlock_read_lock(&rw->rw);
return;
}
CK_CC_INLINE static void
ck_swlock_recursive_read_latchlock(ck_swlock_recursive_t *rw)
{
ck_swlock_read_latchlock(&rw->rw);
return;
}
CK_CC_INLINE static bool
ck_swlock_recursive_read_trylock(ck_swlock_recursive_t *rw)
{
return ck_swlock_read_trylock(&rw->rw);
}
CK_CC_INLINE static void
ck_swlock_recursive_read_unlock(ck_swlock_recursive_t *rw)
{
ck_swlock_read_unlock(&rw->rw);
return;
}
#endif /* _CK_SWLOCK_H */

77
regressions/ck_swlock/validate/validate.c
Unescape View File

@ -48,82 +48,6 @@ static struct affinity a;
static unsigned int locked;
static int nthr;
static ck_swlock_t lock = CK_SWLOCK_INITIALIZER;
static ck_swlock_recursive_t r_lock = CK_SWLOCK_RECURSIVE_INITIALIZER;
static void *
thread_recursive(void *arg)
{
int i = ITERATE;
unsigned int l;
int tid = ck_pr_load_int(arg);
if (aff_iterate(&a)) {
perror("ERROR: Could not affine thread");
exit(EXIT_FAILURE);
}
while (i--) {
if (tid == 0) {
/* Writer */
while (ck_swlock_recursive_write_trylock(&r_lock) == false)
ck_pr_stall();
ck_swlock_recursive_write_lock(&r_lock);
ck_swlock_recursive_write_lock(&r_lock);
ck_swlock_recursive_write_latch(&r_lock);
{
l = ck_pr_load_uint(&locked);
if (l != 0) {
ck_error("ERROR [WR:%d]: %u != 0\n", __LINE__, l);
}
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
ck_pr_inc_uint(&locked);
l = ck_pr_load_uint(&locked);
if (l != 8) {
ck_error("ERROR [WR:%d]: %u != 2\n", __LINE__, l);
}
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
ck_pr_dec_uint(&locked);
l = ck_pr_load_uint(&locked);
if (l != 0) {
ck_error("ERROR [WR:%d]: %u != 0\n", __LINE__, l);
}
}
ck_swlock_recursive_write_unlatch(&r_lock);
ck_swlock_recursive_write_unlock(&r_lock);
ck_swlock_recursive_write_unlock(&r_lock);
ck_swlock_recursive_write_unlock(&r_lock);
}
ck_swlock_recursive_read_latchlock(&r_lock);
{
l = ck_pr_load_uint(&locked);
if (l != 0) {
ck_error("ERROR [RD:%d]: %u != 0\n", __LINE__, l);
}
}
ck_swlock_recursive_read_unlock(&r_lock);
}
return (NULL);
}
#ifdef CK_F_PR_RTM
static void *
@ -524,7 +448,6 @@ main(int argc, char *argv[])
swlock_test(threads, thread_rtm_mix, "rtm-mix");
swlock_test(threads, thread_rtm_adaptive, "rtm-adaptive");
#endif
swlock_test(threads, thread_recursive, "recursive");
return 0;
}

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