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Convert archiver's force_dir_scan variable to an atomic variable.

author Nathan Bossart <nathan@postgresql.org>

2024年2月29日 16:17:55 +0000 (10:17 -0600)

committer Nathan Bossart <nathan@postgresql.org>

2024年2月29日 16:17:55 +0000 (10:17 -0600)

Commit bd5132db55 introduced new atomic read/write functions with
full barrier semantics, which are intended to simplify converting
non-performance-critical code to use atomic variables. This commit
demonstrates one such conversion.

Reviewed-by: Yong Li
Discussion: https://postgr.es/m/20231110205128.GB1315705%40nathanxps13

src/backend/postmaster/pgarch.c patch | blob | blame | history

diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c

index 9c18e4b3efbc698b71925d474e14adbc75e1d00c..04fedfae2fa6791d28d01ac5442e90965d7814c2 100644 (file)

--- a/src/backend/postmaster/pgarch.c

+++ b/src/backend/postmaster/pgarch.c

@@ -45,7 +45,6 @@

#include "storage/proc.h"

#include "storage/procsignal.h"

#include "storage/shmem.h"

-#include "storage/spin.h"

#include "utils/guc.h"

#include "utils/memutils.h"

#include "utils/ps_status.h"

@@ -83,11 +82,9 @@ typedef struct PgArchData

int pgprocno; /* pgprocno of archiver process */

- * Forces a directory scan in pgarch_readyXlog(). Protected by arch_lck.

+ * Forces a directory scan in pgarch_readyXlog().

- bool force_dir_scan;

- slock_t arch_lck;

+ pg_atomic_uint32 force_dir_scan;

} PgArchData;

char *XLogArchiveLibrary = "";

@@ -174,7 +171,7 @@ PgArchShmemInit(void)

/* First time through, so initialize */

MemSet(PgArch, 0, PgArchShmemSize());

PgArch->pgprocno = INVALID_PGPROCNO;

- SpinLockInit(&PgArch->arch_lck);

+ pg_atomic_init_u32(&PgArch->force_dir_scan, 0);

}

@@ -545,18 +542,12 @@ pgarch_readyXlog(char *xlog)

char XLogArchiveStatusDir[MAXPGPATH];

DIR *rldir;

struct dirent *rlde;

- bool force_dir_scan;

* If a directory scan was requested, clear the stored file names and

* proceed.

- SpinLockAcquire(&PgArch->arch_lck);

- force_dir_scan = PgArch->force_dir_scan;

- PgArch->force_dir_scan = false;

- SpinLockRelease(&PgArch->arch_lck);

- if (force_dir_scan)

+ if (pg_atomic_exchange_u32(&PgArch->force_dir_scan, 0) == 1)

arch_files->arch_files_size = 0;

@@ -707,9 +698,7 @@ ready_file_comparator(Datum a, Datum b, void *arg)

void

PgArchForceDirScan(void)

{

- SpinLockAcquire(&PgArch->arch_lck);

- PgArch->force_dir_scan = true;

- SpinLockRelease(&PgArch->arch_lck);

+ pg_atomic_write_membarrier_u32(&PgArch->force_dir_scan, 1);

}

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