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Overview
Comment: | Take extra precautions to ensure access to unixInodeInfo.pUnused is protected by all necessary mutexes. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA3-256: |
8b1e0010b9e0b548a90087f4d25843d2 |
User & Date: | drh 2018-08-13 20:46:18.212 |
Context
2018-08-13
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22:50 | Stop requiring the global VFS mutex to access the unixInodeInfo.pUnused field. The unixInodeInfo mutex is sufficient. (check-in: e3ea43dabf user: drh tags: trunk) | |
20:46 | Take extra precautions to ensure access to unixInodeInfo.pUnused is protected by all necessary mutexes. (check-in: 8b1e0010b9 user: drh tags: trunk) | |
11:32 | Fix an incorrect comment on the unix-nolock VFS object. No functional code changes. (check-in: 90f7c193b4 user: drh tags: trunk) | |
Changes
Changes to src/os_unix.c.
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698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 | ** Function unixMutexHeld() is used to assert() that the global mutex ** is held when required. This function is only used as part of assert() ** statements. e.g. ** ** unixEnterMutex() ** assert( unixMutexHeld() ); ** unixEnterLeave() */ static sqlite3_mutex *unixBigLock = 0; static void unixEnterMutex(void){ sqlite3_mutex_enter(unixBigLock); } static void unixLeaveMutex(void){ sqlite3_mutex_leave(unixBigLock); } #ifdef SQLITE_DEBUG static int unixMutexHeld(void) { return sqlite3_mutex_held(unixBigLock); } #endif | > > > > > > > > > > > > > | 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 | ** Function unixMutexHeld() is used to assert() that the global mutex ** is held when required. This function is only used as part of assert() ** statements. e.g. ** ** unixEnterMutex() ** assert( unixMutexHeld() ); ** unixEnterLeave() ** ** To prevent deadlock, the global unixBigLock must must be acquired ** before the unixInodeInfo.pLockMutex mutex, if both are held. It is ** OK to get the pLockMutex without holding unixBigLock first, but if ** that happens, the unixBigLock mutex must not be acquired until after ** pLockMutex is released. ** ** OK: enter(unixBigLock), enter(pLockInfo) ** OK: enter(unixBigLock) ** OK: enter(pLockInfo) ** ERROR: enter(pLockInfo), enter(unixBigLock) */ static sqlite3_mutex *unixBigLock = 0; static void unixEnterMutex(void){ assert( sqlite3_mutex_notheld(unixBigLock) ); /* Not a recursive mutex */ sqlite3_mutex_enter(unixBigLock); } static void unixLeaveMutex(void){ assert( sqlite3_mutex_held(unixBigLock) ); sqlite3_mutex_leave(unixBigLock); } #ifdef SQLITE_DEBUG static int unixMutexHeld(void) { return sqlite3_mutex_held(unixBigLock); } #endif |
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1107 1108 1109 1110 1111 1112 1113 | ** ** A single inode can have multiple file descriptors, so each unixFile ** structure contains a pointer to an instance of this object and this ** object keeps a count of the number of unixFile pointing to it. ** ** Mutex rules: ** | | > > > > | > > > > > < | > > > > > > > > > > > > > > | 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 | ** ** A single inode can have multiple file descriptors, so each unixFile ** structure contains a pointer to an instance of this object and this ** object keeps a count of the number of unixFile pointing to it. ** ** Mutex rules: ** ** (1) Only the pLockMutex mutex must be held in order to read or write ** any of the locking fields: ** nShared, nLock, eFileLock, or bProcessLock ** ** (2) When nRef>0, then the following fields are unchanging and can ** be read (but not written) without holding any mutex: ** fileId, pLockMutex ** ** (3) The pUnused field may only be changed while holding bo the ** pLockMutex and the bigUnixLock mutex. But it may be read ** while holding either. ** ** (4) With the exceptions above, all the fields may only be read ** or written while holding the global unixBigLock mutex. ** ** Deadlock prevention: The global unixBigLock mutex may not ** be acquired while holding the pLockMutex mutex. If both unixBigLock ** and pLockMutex are needed, then unixBigLock must be acquired first. */ struct unixInodeInfo { struct unixFileId fileId; /* The lookup key */ sqlite3_mutex *pLockMutex; /* Hold this mutex for... */ int nShared; /* Number of SHARED locks held */ int nLock; /* Number of outstanding file locks */ unsigned char eFileLock; /* One of SHARED_LOCK, RESERVED_LOCK etc. */ unsigned char bProcessLock; /* An exclusive process lock is held */ UnixUnusedFd *pUnused; /* Unused file descriptors to close */ int nRef; /* Number of pointers to this structure */ unixShmNode *pShmNode; /* Shared memory associated with this inode */ unixInodeInfo *pNext; /* List of all unixInodeInfo objects */ unixInodeInfo *pPrev; /* .... doubly linked */ #if SQLITE_ENABLE_LOCKING_STYLE unsigned long long sharedByte; /* for AFP simulated shared lock */ #endif #if OS_VXWORKS sem_t *pSem; /* Named POSIX semaphore */ char aSemName[MAX_PATHNAME+2]; /* Name of that semaphore */ #endif }; /* ** A lists of all unixInodeInfo objects. */ static unixInodeInfo *inodeList = 0; /* All unixInodeInfo objects */ #ifdef SQLITE_DEBUG /* ** True if the inode mutex is held, or not. Used only within assert() ** to help verify correct mutex usage. */ int unixFileMutexHeld(unixFile *pFile){ assert( pFile->pInode ); return sqlite3_mutex_held(pFile->pInode->pLockMutex); } int unixFileMutexNotheld(unixFile *pFile){ assert( pFile->pInode ); return sqlite3_mutex_notheld(pFile->pInode->pLockMutex); } #endif /* ** ** This function - unixLogErrorAtLine(), is only ever called via the macro ** unixLogError(). ** ** It is invoked after an error occurs in an OS function and errno has been |
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1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 | /* ** Close all file descriptors accumuated in the unixInodeInfo->pUnused list. */ static void closePendingFds(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; UnixUnusedFd *p; UnixUnusedFd *pNext; for(p=pInode->pUnused; p; p=pNext){ pNext = p->pNext; robust_close(pFile, p->fd, __LINE__); sqlite3_free(p); | > > > < > > < | 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 | /* ** Close all file descriptors accumuated in the unixInodeInfo->pUnused list. */ static void closePendingFds(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; UnixUnusedFd *p; UnixUnusedFd *pNext; assert( unixMutexHeld() ); assert( unixFileMutexNotheld(pFile) ); sqlite3_mutex_enter(pInode->pLockMutex); for(p=pInode->pUnused; p; p=pNext){ pNext = p->pNext; robust_close(pFile, p->fd, __LINE__); sqlite3_free(p); } pInode->pUnused = 0; sqlite3_mutex_leave(pInode->pLockMutex); } /* ** Release a unixInodeInfo structure previously allocated by findInodeInfo(). ** ** The mutex entered using the unixEnterMutex() function must be held ** when this function is called. */ static void releaseInodeInfo(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; assert( unixMutexHeld() ); assert( unixFileMutexNotheld(pFile) ); if( ALWAYS(pInode) ){ pInode->nRef--; if( pInode->nRef==0 ){ assert( pInode->pShmNode==0 ); closePendingFds(pFile); if( pInode->pPrev ){ assert( pInode->pPrev->pNext==pInode ); pInode->pPrev->pNext = pInode->pNext; }else{ assert( inodeList==pInode ); inodeList = pInode->pNext; } if( pInode->pNext ){ assert( pInode->pNext->pPrev==pInode ); pInode->pNext->pPrev = pInode->pPrev; } sqlite3_mutex_free(pInode->pLockMutex); sqlite3_free(pInode); } } } /* ** Given a file descriptor, locate the unixInodeInfo object that ** describes that file descriptor. Create a new one if necessary. The ** return value might be uninitialized if an error occurs. ** |
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1357 1358 1359 1360 1361 1362 1363 | memset(&fileId, 0, sizeof(fileId)); fileId.dev = statbuf.st_dev; #if OS_VXWORKS fileId.pId = pFile->pId; #else fileId.ino = (u64)statbuf.st_ino; #endif | < | 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 | memset(&fileId, 0, sizeof(fileId)); fileId.dev = statbuf.st_dev; #if OS_VXWORKS fileId.pId = pFile->pId; #else fileId.ino = (u64)statbuf.st_ino; #endif pInode = inodeList; while( pInode && memcmp(&fileId, &pInode->fileId, sizeof(fileId)) ){ pInode = pInode->pNext; } if( pInode==0 ){ pInode = sqlite3_malloc64( sizeof(*pInode) ); if( pInode==0 ){ |
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1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 | /* ** Add the file descriptor used by file handle pFile to the corresponding ** pUnused list. */ static void setPendingFd(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; UnixUnusedFd *p = pFile->pPreallocatedUnused; p->pNext = pInode->pUnused; pInode->pUnused = p; pFile->h = -1; pFile->pPreallocatedUnused = 0; | > > > > < > | 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 | /* ** Add the file descriptor used by file handle pFile to the corresponding ** pUnused list. */ static void setPendingFd(unixFile *pFile){ unixInodeInfo *pInode = pFile->pInode; UnixUnusedFd *p = pFile->pPreallocatedUnused; assert( unixMutexHeld() ); assert( unixFileMutexNotheld(pFile) ); sqlite3_mutex_enter(pInode->pLockMutex); p->pNext = pInode->pUnused; pInode->pUnused = p; sqlite3_mutex_leave(pInode->pLockMutex); pFile->h = -1; pFile->pPreallocatedUnused = 0; } /* ** Lower the locking level on file descriptor pFile to eFileLock. eFileLock ** must be either NO_LOCK or SHARED_LOCK. ** ** If the locking level of the file descriptor is already at or below ** the requested locking level, this routine is a no-op. ** ** If handleNFSUnlock is true, then on downgrading an EXCLUSIVE_LOCK to SHARED ** the byte range is divided into 2 parts and the first part is unlocked then ** set to a read lock, then the other part is simply unlocked. This works ** around a bug in BSD NFS lockd (also seen on MacOSX 10.3+) that fails to ** remove the write lock on a region when a read lock is set. */ static int posixUnlock(sqlite3_file *id, int eFileLock, int handleNFSUnlock){ unixFile *pFile = (unixFile*)id; unixInodeInfo *pInode; struct flock lock; int rc = SQLITE_OK; int wantToClosePending = 0; /* True to try to close file old descriptors */ assert( pFile ); OSTRACE(("UNLOCK %d %d was %d(%d,%d) pid=%d (unix)\n", pFile->h, eFileLock, pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared, osGetpid(0))); assert( eFileLock<=SHARED_LOCK ); |
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1984 1985 1986 1987 1988 1989 1990 | /* Decrement the count of locks against this same file. When the ** count reaches zero, close any other file descriptors whose close ** was deferred because of outstanding locks. */ pInode->nLock--; assert( pInode->nLock>=0 ); | | | | > > > > > > > | 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 | /* Decrement the count of locks against this same file. When the ** count reaches zero, close any other file descriptors whose close ** was deferred because of outstanding locks. */ pInode->nLock--; assert( pInode->nLock>=0 ); if( pInode->nLock==0 && pInode->pUnused!=0 ){ wantToClosePending = 1; } } end_unlock: sqlite3_mutex_leave(pInode->pLockMutex); if( rc==SQLITE_OK ){ pFile->eFileLock = eFileLock; if( wantToClosePending ){ unixEnterMutex(); if( pInode->nLock==0 ) closePendingFds(pFile); unixLeaveMutex(); } } return rc; } /* ** Lower the locking level on file descriptor pFile to eFileLock. eFileLock ** must be either NO_LOCK or SHARED_LOCK. ** |
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2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 | ** Close a file. */ static int unixClose(sqlite3_file *id){ int rc = SQLITE_OK; unixFile *pFile = (unixFile *)id; verifyDbFile(pFile); unixUnlock(id, NO_LOCK); unixEnterMutex(); /* unixFile.pInode is always valid here. Otherwise, a different close ** routine (e.g. nolockClose()) would be called instead. */ assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 ); if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){ | > | 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 | ** Close a file. */ static int unixClose(sqlite3_file *id){ int rc = SQLITE_OK; unixFile *pFile = (unixFile *)id; verifyDbFile(pFile); unixUnlock(id, NO_LOCK); assert( unixFileMutexNotheld(pFile) ); unixEnterMutex(); /* unixFile.pInode is always valid here. Otherwise, a different close ** routine (e.g. nolockClose()) would be called instead. */ assert( pFile->pInode->nLock>0 || pFile->pInode->bProcessLock==0 ); if( ALWAYS(pFile->pInode) && pFile->pInode->nLock ){ |
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2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 | ** Close a file. */ static int semXClose(sqlite3_file *id) { if( id ){ unixFile *pFile = (unixFile*)id; semXUnlock(id, NO_LOCK); assert( pFile ); unixEnterMutex(); releaseInodeInfo(pFile); unixLeaveMutex(); closeUnixFile(id); } return SQLITE_OK; } | > | 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 | ** Close a file. */ static int semXClose(sqlite3_file *id) { if( id ){ unixFile *pFile = (unixFile*)id; semXUnlock(id, NO_LOCK); assert( pFile ); assert( unixFileMutexNotheld(pFile) ); unixEnterMutex(); releaseInodeInfo(pFile); unixLeaveMutex(); closeUnixFile(id); } return SQLITE_OK; } |
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3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 | */ static int afpUnlock(sqlite3_file *id, int eFileLock) { int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; unixInodeInfo *pInode; afpLockingContext *context = (afpLockingContext *) pFile->lockingContext; int skipShared = 0; #ifdef SQLITE_TEST int h = pFile->h; #endif assert( pFile ); OSTRACE(("UNLOCK %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock, pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared, | > | 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 | */ static int afpUnlock(sqlite3_file *id, int eFileLock) { int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; unixInodeInfo *pInode; afpLockingContext *context = (afpLockingContext *) pFile->lockingContext; int skipShared = 0; int wantToClosePending = 0; #ifdef SQLITE_TEST int h = pFile->h; #endif assert( pFile ); OSTRACE(("UNLOCK %d %d was %d(%d,%d) pid=%d (afp)\n", pFile->h, eFileLock, pFile->eFileLock, pFile->pInode->eFileLock, pFile->pInode->nShared, |
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3115 3116 3117 3118 3119 3120 3121 | pInode->eFileLock = NO_LOCK; pFile->eFileLock = NO_LOCK; } } if( rc==SQLITE_OK ){ pInode->nLock--; assert( pInode->nLock>=0 ); | | < < | > > > > > > > > | 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 | pInode->eFileLock = NO_LOCK; pFile->eFileLock = NO_LOCK; } } if( rc==SQLITE_OK ){ pInode->nLock--; assert( pInode->nLock>=0 ); if( pInode->nLock==0 && pInode->pUnused!=0 ) wantToClosePending = 1; } } sqlite3_mutex_leave(pInode->pLockMutex); if( rc==SQLITE_OK ){ pFile->eFileLock = eFileLock; if( wantToClosePending ){ unixEnterMutex(); if( pInode->nLock==0 ) closePendingFds(pFile); unixLeaveMutex(); } } return rc; } /* ** Close a file & cleanup AFP specific locking context */ static int afpClose(sqlite3_file *id) { int rc = SQLITE_OK; unixFile *pFile = (unixFile*)id; assert( id!=0 ); afpUnlock(id, NO_LOCK); assert( unixFileMutexNotheld(pFile) ); unixEnterMutex(); if( pFile->pInode && pFile->pInode->nLock ){ /* If there are outstanding locks, do not actually close the file just ** yet because that would clear those locks. Instead, add the file ** descriptor to pInode->aPending. It will be automatically closed when ** the last lock is cleared. */ |
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4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 | if( p==0 ) return SQLITE_NOMEM_BKPT; memset(p, 0, sizeof(*p)); assert( pDbFd->pShm==0 ); /* Check to see if a unixShmNode object already exists. Reuse an existing ** one if present. Create a new one if necessary. */ unixEnterMutex(); pInode = pDbFd->pInode; pShmNode = pInode->pShmNode; if( pShmNode==0 ){ struct stat sStat; /* fstat() info for database file */ #ifndef SQLITE_SHM_DIRECTORY const char *zBasePath = pDbFd->zPath; | > | 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 | if( p==0 ) return SQLITE_NOMEM_BKPT; memset(p, 0, sizeof(*p)); assert( pDbFd->pShm==0 ); /* Check to see if a unixShmNode object already exists. Reuse an existing ** one if present. Create a new one if necessary. */ assert( unixFileMutexNotheld(pDbFd) ); unixEnterMutex(); pInode = pDbFd->pInode; pShmNode = pInode->pShmNode; if( pShmNode==0 ){ struct stat sStat; /* fstat() info for database file */ #ifndef SQLITE_SHM_DIRECTORY const char *zBasePath = pDbFd->zPath; |
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4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 | ** any load or store begun after the barrier. */ static void unixShmBarrier( sqlite3_file *fd /* Database file holding the shared memory */ ){ UNUSED_PARAMETER(fd); sqlite3MemoryBarrier(); /* compiler-defined memory barrier */ unixEnterMutex(); /* Also mutex, for redundancy */ unixLeaveMutex(); } /* ** Close a connection to shared-memory. Delete the underlying ** storage if deleteFlag is true. | > | 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 | ** any load or store begun after the barrier. */ static void unixShmBarrier( sqlite3_file *fd /* Database file holding the shared memory */ ){ UNUSED_PARAMETER(fd); sqlite3MemoryBarrier(); /* compiler-defined memory barrier */ assert( unixFileMutexNotheld((unixFile*)fd) ); unixEnterMutex(); /* Also mutex, for redundancy */ unixLeaveMutex(); } /* ** Close a connection to shared-memory. Delete the underlying ** storage if deleteFlag is true. |
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4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 | /* Free the connection p */ sqlite3_free(p); pDbFd->pShm = 0; sqlite3_mutex_leave(pShmNode->mutex); /* If pShmNode->nRef has reached 0, then close the underlying ** shared-memory file, too */ unixEnterMutex(); assert( pShmNode->nRef>0 ); pShmNode->nRef--; if( pShmNode->nRef==0 ){ if( deleteFlag && pShmNode->h>=0 ){ osUnlink(pShmNode->zFilename); } | > | 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 | /* Free the connection p */ sqlite3_free(p); pDbFd->pShm = 0; sqlite3_mutex_leave(pShmNode->mutex); /* If pShmNode->nRef has reached 0, then close the underlying ** shared-memory file, too */ assert( unixFileMutexNotheld(pDbFd) ); unixEnterMutex(); assert( pShmNode->nRef>0 ); pShmNode->nRef--; if( pShmNode->nRef==0 ){ if( deleteFlag && pShmNode->h>=0 ){ osUnlink(pShmNode->zFilename); } |
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5692 5693 5694 5695 5696 5697 5698 | ** almost certain that an open() call on the same path will also fail. ** For this reason, if an error occurs in the stat() call here, it is ** ignored and -1 is returned. The caller will try to open a new file ** descriptor on the same path, fail, and return an error to SQLite. ** ** Even if a subsequent open() call does succeed, the consequences of ** not searching for a reusable file descriptor are not dire. */ | | > > < > | 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 | ** almost certain that an open() call on the same path will also fail. ** For this reason, if an error occurs in the stat() call here, it is ** ignored and -1 is returned. The caller will try to open a new file ** descriptor on the same path, fail, and return an error to SQLite. ** ** Even if a subsequent open() call does succeed, the consequences of ** not searching for a reusable file descriptor are not dire. */ if( inodeList!=0 && 0==osStat(zPath, &sStat) ){ unixInodeInfo *pInode; pInode = inodeList; while( pInode && (pInode->fileId.dev!=sStat.st_dev || pInode->fileId.ino!=(u64)sStat.st_ino) ){ pInode = pInode->pNext; } if( pInode ){ UnixUnusedFd **pp; assert( sqlite3_mutex_notheld(pInode->pLockMutex) ); sqlite3_mutex_enter(pInode->pLockMutex); for(pp=&pInode->pUnused; *pp && (*pp)->flags!=flags; pp=&((*pp)->pNext)); pUnused = *pp; if( pUnused ){ *pp = pUnused->pNext; } sqlite3_mutex_leave(pInode->pLockMutex); } } unixLeaveMutex(); #endif /* if !OS_VXWORKS */ return pUnused; } |
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