Changeset: 16d91b1f3cff for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/16d91b1f3cff
Modified Files:
common/utils/mutils.c
Branch: Sep2022
Log Message:
Reuse file descriptor when unlocking a file in MT_lockf.
This was already done like that on Windows, now also elsewhere.
Also, updating the linked list for this is a critical section.
diffs (126 lines):
diff --git a/common/utils/mutils.c b/common/utils/mutils.c
--- a/common/utils/mutils.c
+++ b/common/utils/mutils.c
@@ -468,9 +468,17 @@ MT_lockf(const char *filename, int mode)
wchar_t *wfilename;
int fildes;
} *lockedfiles;
+ static CRITICAL_SECTION cs;
+ static bool inited = false;
struct lockedfiles **fpp, *fp;
wchar_t *wfilename;
+ if (!inited) {
+ /* here we're still running single threaded */
+ InitializeCriticalSection(&cs);
+ inited = true; /* only time this is changed */
+ }
+
if ((wfilename = utf8towchar(filename)) == NULL)
return -2;
ov = (OVERLAPPED) {0};
@@ -483,19 +491,21 @@ MT_lockf(const char *filename, int mode)
#endif
if (mode == F_ULOCK) {
+ EnterCriticalSection(&cs);
for (fpp = &lockedfiles; (fp = *fpp) != NULL; fpp = &fp->next) {
if (wcscmp(fp->wfilename, wfilename) == 0) {
+ *fpp = fp->next;
+ LeaveCriticalSection(&cs);
free(fp->wfilename);
fd = fp->fildes;
fh = (HANDLE) _get_osfhandle(fd);
- fp = *fpp;
- *fpp = fp->next;
free(fp);
ret = UnlockFileEx(fh, 0, 1, 0, &ov);
free(wfilename);
return ret ? 0 : -1;
}
}
+ LeaveCriticalSection(&cs);
/* didn't find the locked file, try opening the file
* directly */
fh = CreateFileW(wfilename,
@@ -542,8 +552,10 @@ MT_lockf(const char *filename, int mode)
if ((fp = malloc(sizeof(*fp))) != NULL) {
fp->wfilename = wfilename;
fp->fildes = fd;
+ EnterCriticalSection(&cs);
fp->next = lockedfiles;
lockedfiles = fp;
+ LeaveCriticalSection(&cs);
} else {
free(wfilename);
}
@@ -752,6 +764,8 @@ lockf(int fd, int cmd, off_t len)
}
#endif
+#include <pthread.h>
+
#ifndef O_TEXT
#define O_TEXT 0
#endif
@@ -763,19 +777,57 @@ lockf(int fd, int cmd, off_t len)
int
MT_lockf(const char *filename, int mode)
{
- int fd = open(filename, O_CREAT | O_RDWR | O_TEXT | O_CLOEXEC,
MONETDB_MODE);
+ static struct lockfile {
+ char *filename;
+ int fd;
+ struct lockfile *next;
+ } *lockfiles = NULL;
+ static pthread_mutex_t cs = PTHREAD_MUTEX_INITIALIZER;
+ struct lockfile *fp;
+ int fd;
+ off_t seek;
+
+ if (mode == F_ULOCK) {
+ pthread_mutex_lock(&cs);
+ for (struct lockfile **fpp = &lockfiles; (fp = *fpp) != NULL;
fpp = &fp->next) {
+ if (strcmp(fp->filename, filename) == 0) {
+ *fpp = fp->next;
+ pthread_mutex_unlock(&cs);
+ free(fp->filename);
+ fd = fp->fd;
+ free(fp);
+ seek = lseek(fd, 4, SEEK_SET);
+ int ret = lockf(fd, mode, 1);
+ (void) lseek(fd, seek, SEEK_SET); /* move seek
pointer back */
+ /* do not close fd, it is closed by caller */
+ return ret; /* 0 if unlock
successful, -1 if not */
+ }
+ }
+ }
+ fd = open(filename, O_CREAT | O_RDWR | O_TEXT | O_CLOEXEC,
MONETDB_MODE);
if (fd < 0)
return -2;
- if (lseek(fd, 4, SEEK_SET) >= 0 &&
+ if ((seek = lseek(fd, 4, SEEK_SET)) >= 0 &&
lockf(fd, mode, 1) == 0) {
if (mode == F_ULOCK || mode == F_TEST) {
close(fd);
return 0;
}
+ if ((fp = malloc(sizeof(*fp))) != NULL) {
+ if ((fp->filename = strdup(filename)) != NULL) {
+ fp->fd = fd;
+ pthread_mutex_lock(&cs);
+ fp->next = lockfiles;
+ lockfiles = fp;
+ pthread_mutex_unlock(&cs);
+ } else {
+ free(fp);
+ }
+ }
/* do not close else we lose the lock we want */
- (void) lseek(fd, 0, SEEK_SET); /* move seek pointer back */
+ (void) lseek(fd, seek, SEEK_SET); /* move seek pointer back */
return fd;
}
close(fd);
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