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Replace LOCKTAGs with LWLocks #111

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Replace LOCKTAGs with LWLocks #111

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6 changes: 2 additions & 4 deletions collector.c
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Original file line number Diff line number Diff line change
Expand Up @@ -426,12 +426,10 @@ pgws_collector_main(Datum main_arg)
/* Handle request if any */
if (pgws_collector_hdr->request != NO_REQUEST)
{
LOCKTAG tag;
SHMRequest request;

pgws_init_lock_tag(&tag, PGWS_COLLECTOR_LOCK);
LWLockAcquire(collector_lock, LW_EXCLUSIVE);

LockAcquire(&tag, ExclusiveLock, false, false);
request = pgws_collector_hdr->request;
pgws_collector_hdr->request = NO_REQUEST;

Expand Down Expand Up @@ -475,7 +473,7 @@ pgws_collector_main(Datum main_arg)
hash_destroy(profile_hash);
profile_hash = make_profile_hash();
}
LockRelease(&tag, ExclusiveLock, false);
LWLockRelease(collector_lock);
}
}

Expand Down
59 changes: 26 additions & 33 deletions pg_wait_sampling.c
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Original file line number Diff line number Diff line change
Expand Up @@ -60,10 +60,13 @@ shm_mq *pgws_collector_mq = NULL;
uint64 *pgws_proc_queryids = NULL;
CollectorShmqHeader *pgws_collector_hdr = NULL;

/* Receiver (backend) local shm_mq pointers and lock */
/* Receiver (backend) local shm_mq pointers */
static shm_mq *recv_mq = NULL;
static shm_mq_handle *recv_mqh = NULL;
static LOCKTAG queueTag;

/* LWLock pointers */
LWLock *queue_lock;
LWLock *collector_lock;

/* Hook functions */
#if PG_VERSION_NUM >= 150000
Expand Down Expand Up @@ -239,6 +242,10 @@ pgws_shmem_request(void)
prev_shmem_request_hook();

RequestAddinShmemSpace(pgws_shmem_size());

/* We request two different LWLock Tranches for ease of use */
RequestNamedLWLockTranche(PGWS_QUEUE_LOCK_NAME, 1);
RequestNamedLWLockTranche(PGWS_COLLECTOR_LOCK_NAME, 1);
}
#endif

Expand All @@ -258,6 +265,9 @@ pgws_shmem_startup(void)
if (!found)
{
/* Create shared objects */
queue_lock = &(GetNamedLWLockTranche(PGWS_QUEUE_LOCK_NAME))->lock;
collector_lock = &(GetNamedLWLockTranche(PGWS_COLLECTOR_LOCK_NAME))->lock;

toc = shm_toc_create(PG_WAIT_SAMPLING_MAGIC, pgws, segsize);

pgws_collector_hdr = shm_toc_allocate(toc, sizeof(CollectorShmqHeader));
Expand Down Expand Up @@ -302,7 +312,7 @@ pgws_cleanup_callback(int code, Datum arg)
{
elog(DEBUG3, "pg_wait_sampling cleanup: detaching shm_mq and releasing queue lock");
shm_mq_detach(recv_mqh);
LockRelease(&queueTag, ExclusiveLock, false);
LWLockRelease(queue_lock);
}

/*
Expand All @@ -322,9 +332,13 @@ _PG_init(void)
* resources in pgws_shmem_startup().
*
* If you change code here, don't forget to also report the modifications
* in pgsp_shmem_request() for pg15 and later.
* in pgws_shmem_request() for pg15 and later.
*/
RequestAddinShmemSpace(pgws_shmem_size());

/* We request two different LWLock Tranches for ease of use */
RequestNamedLWLockTranche(PGWS_QUEUE_LOCK_NAME, 1);
RequestNamedLWLockTranche(PGWS_COLLECTOR_LOCK_NAME, 1);
#endif

pgws_register_wait_collector();
Expand Down Expand Up @@ -619,22 +633,10 @@ typedef struct
ProfileItem *items;
} Profile;

void
pgws_init_lock_tag(LOCKTAG *tag, uint32 lock)
{
tag->locktag_field1 = PG_WAIT_SAMPLING_MAGIC;
tag->locktag_field2 = lock;
tag->locktag_field3 = 0;
tag->locktag_field4 = 0;
tag->locktag_type = LOCKTAG_USERLOCK;
tag->locktag_lockmethodid = USER_LOCKMETHOD;
}

/* Get array (history or profile data) from shared memory */
static void *
receive_array(SHMRequest request, Size item_size, Size *count)
{
LOCKTAG collectorTag;
shm_mq_result res;
Size len,
i;
Expand All @@ -644,14 +646,11 @@ receive_array(SHMRequest request, Size item_size, Size *count)
MemoryContext oldctx;

/* Ensure nobody else trying to send request to queue */
pgws_init_lock_tag(&queueTag, PGWS_QUEUE_LOCK);
LockAcquire(&queueTag, ExclusiveLock, false, false);

pgws_init_lock_tag(&collectorTag, PGWS_COLLECTOR_LOCK);
LockAcquire(&collectorTag, ExclusiveLock, false, false);
LWLockAcquire(queue_lock, LW_EXCLUSIVE);
LWLockAcquire(collector_lock, LW_EXCLUSIVE);
recv_mq = shm_mq_create(pgws_collector_mq, COLLECTOR_QUEUE_SIZE);
pgws_collector_hdr->request = request;
LockRelease(&collectorTag, ExclusiveLock, false);
LWLockRelease(collector_lock);

/*
* Check that the collector was started to avoid NULL
Expand Down Expand Up @@ -711,7 +710,7 @@ receive_array(SHMRequest request, Size item_size, Size *count)

/* We still have to detach and release lock during normal operation. */
shm_mq_detach(recv_mqh);
LockRelease(&queueTag, ExclusiveLock, false);
LWLockRelease(queue_lock);

return result;
}
Expand Down Expand Up @@ -814,18 +813,12 @@ PG_FUNCTION_INFO_V1(pg_wait_sampling_reset_profile);
Datum
pg_wait_sampling_reset_profile(PG_FUNCTION_ARGS)
{
LOCKTAG collectorTag;

check_shmem();

pgws_init_lock_tag(&queueTag, PGWS_QUEUE_LOCK);

LockAcquire(&queueTag, ExclusiveLock, false, false);

pgws_init_lock_tag(&collectorTag, PGWS_COLLECTOR_LOCK);
LockAcquire(&collectorTag, ExclusiveLock, false, false);
LWLockAcquire(queue_lock, LW_EXCLUSIVE);
LWLockAcquire(collector_lock, LW_EXCLUSIVE);
pgws_collector_hdr->request = PROFILE_RESET;
LockRelease(&collectorTag, ExclusiveLock, false);
LWLockRelease(collector_lock);

/*
* Check that the collector was started to avoid NULL
Expand All @@ -837,7 +830,7 @@ pg_wait_sampling_reset_profile(PG_FUNCTION_ARGS)

SetLatch(pgws_collector_hdr->latch);

LockRelease(&queueTag, ExclusiveLock, false);
LWLockRelease(queue_lock);

PG_RETURN_VOID();
}
Expand Down
11 changes: 7 additions & 4 deletions pg_wait_sampling.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,13 +13,14 @@
#include "datatype/timestamp.h"
#include "storage/latch.h"
#include "storage/lock.h"
#include "storage/lwlock.h"
#include "storage/shm_mq.h"

#define PG_WAIT_SAMPLING_MAGIC 0xCA94B107
#define COLLECTOR_QUEUE_SIZE (16 * 1024)
#define HISTORY_TIME_MULTIPLIER 10
#define PGWS_QUEUE_LOCK 0
#define PGWS_COLLECTOR_LOCK 1
#define PGWS_QUEUE_LOCK_NAME "pgws_queue_lock"
#define PGWS_COLLECTOR_LOCK_NAME "pgws_collector_lock"

typedef struct
{
Expand Down Expand Up @@ -68,10 +69,12 @@ extern int pgws_profileQueries;
extern bool pgws_sampleCpu;

/* pg_wait_sampling.c */
extern CollectorShmqHeader *pgws_collector_hdr;
extern shm_mq *pgws_collector_mq;
extern uint64 *pgws_proc_queryids;
extern void pgws_init_lock_tag(LOCKTAG *tag, uint32 lock);
extern CollectorShmqHeader *pgws_collector_hdr;

extern LWLock *collector_lock;

extern bool pgws_should_sample_proc(PGPROC *proc, int *pid_p, uint32 *wait_event_info_p);

/* collector.c */
Expand Down