Rework mutexes on the SHM implemention for os_unix to avoid a deadlock during
WAL recovery. FossilOrigin-Name: 1a0f69bef2c489e81a3d4b910b426972e9ed4054
This commit is contained in:
drh
parent
5cf53537a8
commit
77b95a379c
24
manifest
24
manifest
@ -1,5 +1,8 @@
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C Support\scompile-time\soption\sSQLITE_OMIT_WAL,\sfor\sbuilding\swithout\sWAL\ssupport.
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D 2010-05-01T16:40:20
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-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA1
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C Rework\smutexes\son\sthe\sSHM\simplemention\sfor\sos_unix\sto\savoid\sa\sdeadlock\sduring\nWAL\srecovery.
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D 2010-05-01T17:50:38
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F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
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F Makefile.in d83a0ffef3dcbfb08b410a6c6dd6c009ec9167fb
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F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
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@ -150,7 +153,7 @@ F src/os.c 8bc63cf91e9802e2b807198e54e50227fa889306
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F src/os.h 534b082c3cb349ad05fa6fa0b06087e022af282c
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F src/os_common.h 0d6ee583b6ee3185eb9d951f890c6dd03021a08d
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F src/os_os2.c 8ad77a418630d7dee91d1bb04f79c2096301d3a0
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F src/os_unix.c 27ec47f27987b9f25bc55df5e458f7f380730f66
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F src/os_unix.c d402146bd3731575ff399d2ebcdc0867034e8451
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F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1
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F src/pager.c e9c7fe979b32a3c5bf4216d8fbe1cf8beff8a1b8
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F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c
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@ -808,7 +811,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
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F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
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F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
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F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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P dcabc90ca588281fa7a290972ec8af6816932489
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R e813455665cf7f3ad3b5157515fc2fe7
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U dan
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Z 955de6008d5a15476ae5c3900eb59d71
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P 9b230c43dfa112e3e1589f9775926807bd36b36e
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R 70dfb91700ac677788e5556f2fcdd9f6
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U drh
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Z aec6f98e0ebcce7f7132104408636399
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@ -1 +1 @@
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9b230c43dfa112e3e1589f9775926807bd36b36e
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1a0f69bef2c489e81a3d4b910b426972e9ed4054
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@ -4594,7 +4594,6 @@ struct unixShmFile {
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struct unixFileId fid; /* Unique file identifier */
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sqlite3_mutex *mutex; /* Mutex to access this object */
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sqlite3_mutex *mutexBuf; /* Mutex to access zBuf[] */
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sqlite3_mutex *mutexRecov; /* The RECOVER mutex */
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char *zFilename; /* Name of the file */
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int h; /* Open file descriptor */
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int szMap; /* Size of the mapping of file into memory */
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@ -4633,7 +4632,6 @@ struct unixShm {
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u8 readLock; /* Which of the two read-lock states to use */
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u8 hasMutex; /* True if holding the unixShmFile mutex */
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u8 hasMutexBuf; /* True if holding pFile->mutexBuf */
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u8 hasMutexRecov; /* True if holding pFile->mutexRecov */
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u8 sharedMask; /* Mask of shared locks held */
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u8 exclMask; /* Mask of exclusive locks held */
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#ifdef SQLITE_DEBUG
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@ -4909,7 +4907,6 @@ static void unixShmPurge(void){
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if( p->nRef==0 ){
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if( p->mutex ) sqlite3_mutex_free(p->mutex);
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if( p->mutexBuf ) sqlite3_mutex_free(p->mutexBuf);
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if( p->mutexRecov ) sqlite3_mutex_free(p->mutexRecov);
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if( p->h>=0 ) close(p->h);
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*pp = p->pNext;
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sqlite3_free(p);
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@ -4979,11 +4976,6 @@ static int unixShmOpen(
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rc = SQLITE_NOMEM;
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goto shm_open_err;
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}
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pFile->mutexRecov = sqlite3_mutex_alloc(SQLITE_MUTEX_FAST);
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if( pFile->mutexRecov==0 ){
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rc = SQLITE_NOMEM;
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goto shm_open_err;
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}
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pFile->h = open(zName, O_RDWR|O_CREAT, 0664);
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if( pFile->h<0 ){
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@ -5124,8 +5116,19 @@ static int unixShmSize(
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** whatever mapping size is convenient.
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**
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** *ppBuf is made to point to the memory which is a mapping of the
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** underlying storage. This segment is locked. unixShmRelease()
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** must be called to release the lock.
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** underlying storage. A mutex is acquired to prevent other threads
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** from running while *ppBuf is in use in order to prevent other threads
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** remapping *ppBuf out from under this thread. The unixShmRelease()
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** call will release the mutex. However, if the lock state is CHECKPOINT,
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** the mutex is not acquired because CHECKPOINT will never remap the
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** buffer. RECOVER might remap, though, so CHECKPOINT will acquire
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** the mutex if and when it promotes to RECOVER.
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**
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** RECOVER needs to be atomic. The same mutex that prevents *ppBuf from
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** being remapped also prevents more than one thread from being in
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** RECOVER at a time. But, RECOVER sometimes wants to remap itself.
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** To prevent RECOVER from losing its lock while remapping, the
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** mutex is not released by unixShmRelease() when in RECOVER.
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**
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** *pNewMapSize is set to the size of the mapping.
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**
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@ -5142,7 +5145,7 @@ static int unixShmGet(
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unixShmFile *pFile = p->pFile;
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int rc = SQLITE_OK;
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if( p->lockState!=SQLITE_SHM_CHECKPOINT ){
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if( p->lockState!=SQLITE_SHM_CHECKPOINT && p->hasMutexBuf==0 ){
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sqlite3_mutex_enter(pFile->mutexBuf);
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p->hasMutexBuf = 1;
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}
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@ -5170,10 +5173,16 @@ static int unixShmGet(
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/*
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** Release the lock held on the shared memory segment to that other
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** threads are free to resize it if necessary.
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**
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** If the lock is not currently held, this routine is a harmless no-op.
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**
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** If the shared-memory object is in lock state RECOVER, then we do not
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** really want to release the lock, so in that case too, this routine
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** is a no-op.
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*/
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static int unixShmRelease(sqlite3_shm *pSharedMem){
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unixShm *p = (unixShm*)pSharedMem;
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if( p->hasMutexBuf ){
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if( p->hasMutexBuf && p->lockState!=SQLITE_SHM_RECOVER ){
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unixShmFile *pFile = p->pFile;
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sqlite3_mutex_leave(pFile->mutexBuf);
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p->hasMutexBuf = 0;
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@ -5235,6 +5244,11 @@ static int unixShmLock(
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OSTRACE(("SHM-LOCK shmid-%d, pid-%d request %s->%s\n",
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p->id, getpid(), azLkName[p->lockState], azLkName[desiredLock]));
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if( desiredLock==SQLITE_SHM_RECOVER && !p->hasMutexBuf ){
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sqlite3_mutex_enter(pFile->mutexBuf);
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p->hasMutexBuf = 1;
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}
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sqlite3_mutex_enter(pFile->mutex);
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switch( desiredLock ){
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case SQLITE_SHM_UNLOCK: {
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@ -5268,7 +5282,6 @@ static int unixShmLock(
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}else{
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assert( p->lockState==SQLITE_SHM_RECOVER );
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unixShmUnlock(pFile, p, UNIX_SHM_MUTEX);
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sqlite3_mutex_leave(pFile->mutexRecov);
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p->lockState = p->readLock;
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rc = SQLITE_OK;
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}
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@ -5289,7 +5302,6 @@ static int unixShmLock(
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|| p->lockState==SQLITE_SHM_RECOVER );
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if( p->lockState==SQLITE_SHM_RECOVER ){
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unixShmUnlock(pFile, p, UNIX_SHM_MUTEX);
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sqlite3_mutex_leave(pFile->mutexRecov);
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p->lockState = SQLITE_SHM_CHECKPOINT;
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rc = SQLITE_OK;
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}
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@ -5312,9 +5324,7 @@ static int unixShmLock(
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assert( p->lockState==SQLITE_SHM_READ
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|| p->lockState==SQLITE_SHM_READ_FULL
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|| p->lockState==SQLITE_SHM_CHECKPOINT );
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sqlite3_mutex_leave(pFile->mutex);
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sqlite3_mutex_enter(pFile->mutexRecov);
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sqlite3_mutex_enter(pFile->mutex);
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assert( sqlite3_mutex_held(pFile->mutexBuf) );
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rc = unixShmExclusiveLock(pFile, p, UNIX_SHM_MUTEX);
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if( rc==SQLITE_OK ){
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p->lockState = SQLITE_SHM_RECOVER;
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