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Simplifications to the SHM locking implementation in os_unix.c.

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FossilOrigin-Name: 9de05bfb09e29bafdf5782263330fe8eefcfaba3
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drh
2010-05-05 18:20:07 +00:00
parent 3289c5efc8
commit 4bc79def36
3 changed files with 26 additions and 34 deletions
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18
manifest
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@@ -1,8 +1,8 @@
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C Prohibit\sbackup\sif\sthe\sdestination\sis\susing\sWAL\sand\shas\sa\sdifferent\spage\nsize\sfrom\sthe\ssource. C Simplifications\sto\sthe\sSHM\slocking\simplementation\sin\sos_unix.c.
D 2010-05-05T16:23:27 D 2010-05-05T18:20:07
F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
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F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -153,7 +153,7 @@ F src/os.c aec6922553585a25d5655666defc125a7e217674
F src/os.h b389844e5469a2918e8a45fe6ae52b4c28dfb2b2 F src/os.h b389844e5469a2918e8a45fe6ae52b4c28dfb2b2
F src/os_common.h 0d6ee583b6ee3185eb9d951f890c6dd03021a08d F src/os_common.h 0d6ee583b6ee3185eb9d951f890c6dd03021a08d
F src/os_os2.c 8ad77a418630d7dee91d1bb04f79c2096301d3a0 F src/os_os2.c 8ad77a418630d7dee91d1bb04f79c2096301d3a0
F src/os_unix.c 7ab8d2fe59954dca619af3e1bbd4789f5032fece F src/os_unix.c 623a195fbcdb7b92cf275acf3ced2388459519a4
F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1 F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1
F src/pager.c 224df6ad5f8c1fed238570092199db1e57233779 F src/pager.c 224df6ad5f8c1fed238570092199db1e57233779
F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c
@@ -812,14 +812,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
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F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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7bd44794c482beee16c684712545275e2bf63dfa 9de05bfb09e29bafdf5782263330fe8eefcfaba3

40
src/os_unix.c
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@@ -4648,7 +4648,6 @@ struct unixShm {
unixShmFile *pFile; /* The underlying unixShmFile object */ unixShmFile *pFile; /* The underlying unixShmFile object */
unixShm *pNext; /* Next unixShm with the same unixShmFile */ unixShm *pNext; /* Next unixShm with the same unixShmFile */
u8 lockState; /* Current lock state */ u8 lockState; /* Current lock state */
u8 readLock; /* Which of the two read-lock states to use */
u8 hasMutex; /* True if holding the unixShmFile mutex */ u8 hasMutex; /* True if holding the unixShmFile mutex */
u8 hasMutexBuf; /* True if holding pFile->mutexBuf */ u8 hasMutexBuf; /* True if holding pFile->mutexBuf */
u8 sharedMask; /* Mask of shared locks held */ u8 sharedMask; /* Mask of shared locks held */
@@ -4667,8 +4666,7 @@ struct unixShm {
** Constants used for locking ** Constants used for locking
*/ */
#define UNIX_SHM_BASE 32 /* Byte offset of the first lock byte */ #define UNIX_SHM_BASE 32 /* Byte offset of the first lock byte */
#define UNIX_SHM_MUTEX 0x01 /* Mask for MUTEX lock */ #define UNIX_SHM_DMS 0x01 /* Mask for Dead-Man-Switch lock */
#define UNIX_SHM_DMS 0x04 /* Mask for Dead-Man-Switch lock */
#define UNIX_SHM_A 0x10 /* Mask for region locks... */ #define UNIX_SHM_A 0x10 /* Mask for region locks... */
#define UNIX_SHM_B 0x20 #define UNIX_SHM_B 0x20
#define UNIX_SHM_C 0x40 #define UNIX_SHM_C 0x40
@@ -4695,13 +4693,12 @@ static const char *unixShmLockString(u8 mask){
iBuf += 8; iBuf += 8;
if( iBuf>=sizeof(zBuf) ) iBuf = 0; if( iBuf>=sizeof(zBuf) ) iBuf = 0;
z[0] = (mask & UNIX_SHM_MUTEX) ? 'M' : '.'; z[0] = (mask & UNIX_SHM_DMS) ? 'S' : '.';
z[1] = (mask & UNIX_SHM_DMS) ? 'S' : '.'; z[1] = (mask & UNIX_SHM_A) ? 'A' : '.';
z[2] = (mask & UNIX_SHM_A) ? 'A' : '.'; z[2] = (mask & UNIX_SHM_B) ? 'B' : '.';
z[3] = (mask & UNIX_SHM_B) ? 'B' : '.'; z[3] = (mask & UNIX_SHM_C) ? 'C' : '.';
z[4] = (mask & UNIX_SHM_C) ? 'C' : '.'; z[4] = (mask & UNIX_SHM_D) ? 'D' : '.';
z[5] = (mask & UNIX_SHM_D) ? 'D' : '.'; z[5] = 0;
z[6] = 0;
return z; return z;
} }
#endif /* SQLITE_DEBUG */ #endif /* SQLITE_DEBUG */
@@ -4712,7 +4709,7 @@ static const char *unixShmLockString(u8 mask){
** lockMask might contain multiple bits but all bits are guaranteed ** lockMask might contain multiple bits but all bits are guaranteed
** to be contiguous. ** to be contiguous.
** **
** Locks block if the UNIX_SHM_MUTEX bit is set and are non-blocking ** Locks block if the mask is exactly UNIX_SHM_C and are non-blocking
** otherwise. ** otherwise.
*/ */
static int unixShmSystemLock( static int unixShmSystemLock(
@@ -4733,7 +4730,7 @@ static int unixShmSystemLock(
memset(&f, 0, sizeof(f)); memset(&f, 0, sizeof(f));
f.l_type = lockType; f.l_type = lockType;
f.l_whence = SEEK_SET; f.l_whence = SEEK_SET;
if( (lockMask & UNIX_SHM_MUTEX)!=0 && lockType!=F_UNLCK ){ if( lockMask==UNIX_SHM_C && lockType!=F_UNLCK ){
lockOp = F_SETLKW; lockOp = F_SETLKW;
OSTRACE(("SHM-LOCK requesting blocking lock\n")); OSTRACE(("SHM-LOCK requesting blocking lock\n"));
}else{ }else{
@@ -5029,10 +5026,6 @@ static int unixShmOpen(
/* Check to see if another process is holding the dead-man switch. /* Check to see if another process is holding the dead-man switch.
** If not, truncate the file to zero length. ** If not, truncate the file to zero length.
*/ */
if( unixShmSystemLock(pFile, F_WRLCK, UNIX_SHM_MUTEX) ){
rc = SQLITE_IOERR_LOCK;
goto shm_open_err;
}
if( unixShmSystemLock(pFile, F_WRLCK, UNIX_SHM_DMS)==SQLITE_OK ){ if( unixShmSystemLock(pFile, F_WRLCK, UNIX_SHM_DMS)==SQLITE_OK ){
if( ftruncate(pFile->h, 0) ){ if( ftruncate(pFile->h, 0) ){
rc = SQLITE_IOERR; rc = SQLITE_IOERR;
@@ -5041,7 +5034,6 @@ static int unixShmOpen(
if( rc==SQLITE_OK ){ if( rc==SQLITE_OK ){
rc = unixShmSystemLock(pFile, F_RDLCK, UNIX_SHM_DMS); rc = unixShmSystemLock(pFile, F_RDLCK, UNIX_SHM_DMS);
} }
unixShmSystemLock(pFile, F_UNLCK, UNIX_SHM_MUTEX);
if( rc ) goto shm_open_err; if( rc ) goto shm_open_err;
} }
@@ -5321,21 +5313,21 @@ static int unixShmLock(
if( rc==SQLITE_BUSY ){ if( rc==SQLITE_BUSY ){
rc = unixShmSharedLock(pFile, p, UNIX_SHM_D); rc = unixShmSharedLock(pFile, p, UNIX_SHM_D);
if( rc==SQLITE_OK ){ if( rc==SQLITE_OK ){
p->lockState = p->readLock = SQLITE_SHM_READ_FULL; p->lockState = SQLITE_SHM_READ_FULL;
} }
}else{ }else{
unixShmUnlock(pFile, p, UNIX_SHM_B); unixShmUnlock(pFile, p, UNIX_SHM_B);
p->lockState = p->readLock = SQLITE_SHM_READ; p->lockState = SQLITE_SHM_READ;
} }
} }
}else if( p->lockState==SQLITE_SHM_WRITE ){ }else if( p->lockState==SQLITE_SHM_WRITE ){
rc = unixShmSharedLock(pFile, p, UNIX_SHM_A); rc = unixShmSharedLock(pFile, p, UNIX_SHM_A);
unixShmUnlock(pFile, p, UNIX_SHM_C|UNIX_SHM_D); unixShmUnlock(pFile, p, UNIX_SHM_C|UNIX_SHM_D);
p->lockState = p->readLock = SQLITE_SHM_READ; p->lockState = SQLITE_SHM_READ;
}else{ }else{
assert( p->lockState==SQLITE_SHM_RECOVER ); assert( p->lockState==SQLITE_SHM_RECOVER );
unixShmUnlock(pFile, p, UNIX_SHM_MUTEX); unixShmUnlock(pFile, p, UNIX_SHM_C);
p->lockState = p->readLock; p->lockState = SQLITE_SHM_READ;
rc = SQLITE_OK; rc = SQLITE_OK;
} }
break; break;
@@ -5354,7 +5346,7 @@ static int unixShmLock(
|| p->lockState==SQLITE_SHM_PENDING || p->lockState==SQLITE_SHM_PENDING
|| p->lockState==SQLITE_SHM_RECOVER ); || p->lockState==SQLITE_SHM_RECOVER );
if( p->lockState==SQLITE_SHM_RECOVER ){ if( p->lockState==SQLITE_SHM_RECOVER ){
unixShmUnlock(pFile, p, UNIX_SHM_MUTEX); unixShmUnlock(pFile, p, UNIX_SHM_C);
p->lockState = SQLITE_SHM_CHECKPOINT; p->lockState = SQLITE_SHM_CHECKPOINT;
rc = SQLITE_OK; rc = SQLITE_OK;
} }
@@ -5378,7 +5370,7 @@ static int unixShmLock(
|| p->lockState==SQLITE_SHM_READ_FULL || p->lockState==SQLITE_SHM_READ_FULL
|| p->lockState==SQLITE_SHM_CHECKPOINT ); || p->lockState==SQLITE_SHM_CHECKPOINT );
assert( sqlite3_mutex_held(pFile->mutexBuf) ); assert( sqlite3_mutex_held(pFile->mutexBuf) );
rc = unixShmExclusiveLock(pFile, p, UNIX_SHM_MUTEX); rc = unixShmExclusiveLock(pFile, p, UNIX_SHM_C);
if( rc==SQLITE_OK ){ if( rc==SQLITE_OK ){
p->lockState = SQLITE_SHM_RECOVER; p->lockState = SQLITE_SHM_RECOVER;
} }