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Add infrastructure to support for using F_SETLKW with a timeout on system

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that support that functionality.  Requires SQLITE_ENABLE_SETLK_TIMEOUT.

FossilOrigin-Name: 2e54a7433ece4eb27e71bda6f2d121d5aa46ddd5a481357d8543d1432aaad689
This commit is contained in:
drh
2018-03-26 17:40:53 +00:00
parent 80262896d6
commit f0119b2e1b
7 changed files with 122 additions and 27 deletions
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55
src/os_unix.c
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@@ -229,6 +229,9 @@ struct unixFile {
#if SQLITE_ENABLE_LOCKING_STYLE || defined(__APPLE__)
unsigned fsFlags; /* cached details from statfs() */
#endif
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
unsigned iBusyTimeout; /* Wait this many millisec on locks */
#endif
#if OS_VXWORKS
struct vxworksFileId *pId; /* Unique file ID */
#endif
@@ -1465,6 +1468,46 @@ static int unixCheckReservedLock(sqlite3_file *id, int *pResOut){
return rc;
}
/*
** Set a posix-advisory-lock.
**
** There are two versions of this routine. If compiled with
** SQLITE_ENABLE_SETLK_TIMEOUT then the routine has an extra parameter
** which is a pointer to a unixFile. If the unixFile->iBusyTimeout
** value is set, then it is the number of milliseconds to wait before
** failing the lock. The iBusyTimeout value is always reset back to
** zero on each call.
**
** If SQLITE_ENABLE_SETLK_TIMEOUT is not defined, then do a non-blocking
** attempt to set the lock.
*/
#ifndef SQLITE_ENABLE_SETLK_TIMEOUT
# define osSetPosixAdvisoryLock(h,x,t) osFcntl(h,F_SETLK,x)
#else
static int osSetPosixAdvisoryLock(
int h, /* The file descriptor on which to take the lock */
struct flock *pLock, /* The description of the lock */
unixFile *pFile /* Structure holding timeout value */
){
int rc = osFcntl(h,F_SETLK,pLock);
if( rc<0 && pFile->iBusyTimeout>0 ){
/* On systems that support some kind of blocking file lock with a timeout,
** make appropriate changes here to invoke that blocking file lock. On
** generic posix, however, there is no such API. So we simply try the
** lock once every millisecond until either the timeout expires, or until
** the lock is obtained. */
do{
usleep(1000);
rc = osFcntl(h,F_SETLK,pLock);
pFile->iBusyTimeout--;
}while( rc<0 && pFile->iBusyTimeout>0 );
pFile->iBusyTimeout = 0;
}
return rc;
}
#endif /* SQLITE_ENABLE_SETLK_TIMEOUT */
/*
** Attempt to set a system-lock on the file pFile. The lock is
** described by pLock.
@@ -1497,7 +1540,7 @@ static int unixFileLock(unixFile *pFile, struct flock *pLock){
lock.l_start = SHARED_FIRST;
lock.l_len = SHARED_SIZE;
lock.l_type = F_WRLCK;
rc = osFcntl(pFile->h, F_SETLK, &lock);
rc = osSetPosixAdvisoryLock(pFile->h, &lock, pFile);
if( rc<0 ) return rc;
pInode->bProcessLock = 1;
pInode->nLock++;
@@ -1505,7 +1548,7 @@ static int unixFileLock(unixFile *pFile, struct flock *pLock){
rc = 0;
}
}else{
rc = osFcntl(pFile->h, F_SETLK, pLock);
rc = osSetPosixAdvisoryLock(pFile->h, pLock, pFile);
}
return rc;
}
@@ -3865,6 +3908,12 @@ static int unixFileControl(sqlite3_file *id, int op, void *pArg){
*(int*)pArg = fileHasMoved(pFile);
return SQLITE_OK;
}
#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
case SQLITE_FCNTL_LOCK_TIMEOUT: {
pFile->iBusyTimeout = *(int*)pArg;
return SQLITE_OK;
}
#endif
#if SQLITE_MAX_MMAP_SIZE>0
case SQLITE_FCNTL_MMAP_SIZE: {
i64 newLimit = *(i64*)pArg;
@@ -4184,7 +4233,7 @@ static int unixShmSystemLock(
f.l_whence = SEEK_SET;
f.l_start = ofst;
f.l_len = n;
rc = osFcntl(pShmNode->h, F_SETLK, &f);
rc = osSetPosixAdvisoryLock(pShmNode->h, &f, pFile);
rc = (rc!=(-1)) ? SQLITE_OK : SQLITE_BUSY;
}