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Define an invariant to guarantee deadlock-free operation of SHM in os_unix.c

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and check that invariant with assert() statements.

FossilOrigin-Name: 6af2dca75b8139134ea394c1d71aefc6523f02e9
This commit is contained in:
drh
2010-05-01 17:57:36 +00:00
parent 77b95a379c
commit bee6f4ebe2
3 changed files with 19 additions and 10 deletions
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18
manifest
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@@ -1,8 +1,8 @@
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Hash: SHA1 Hash: SHA1
C Rework\smutexes\son\sthe\sSHM\simplemention\sfor\sos_unix\sto\savoid\sa\sdeadlock\sduring\nWAL\srecovery. C Define\san\sinvariant\sto\sguarantee\sdeadlock-free\soperation\sof\sSHM\sin\sos_unix.c\nand\scheck\sthat\sinvariant\swith\sassert()\sstatements.
D 2010-05-01T17:50:38 D 2010-05-01T17:57:36
F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
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@@ -153,7 +153,7 @@ F src/os.c 8bc63cf91e9802e2b807198e54e50227fa889306
F src/os.h 534b082c3cb349ad05fa6fa0b06087e022af282c F src/os.h 534b082c3cb349ad05fa6fa0b06087e022af282c
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 d402146bd3731575ff399d2ebcdc0867034e8451 F src/os_unix.c bb8b65d92a79b4b1311fad7cae8a697dea0b8838
F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1 F src/os_win.c a8fc01d8483be472e495793c01064fd87e56a5c1
F src/pager.c e9c7fe979b32a3c5bf4216d8fbe1cf8beff8a1b8 F src/pager.c e9c7fe979b32a3c5bf4216d8fbe1cf8beff8a1b8
F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c F src/pager.h 934b598583a9d936bb13c37d62a2fe68ac48781c
@@ -811,14 +811,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
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F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
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1a0f69bef2c489e81a3d4b910b426972e9ed4054 6af2dca75b8139134ea394c1d71aefc6523f02e9

9
src/os_unix.c
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@@ -4589,6 +4589,12 @@ typedef struct unixShmFile unixShmFile;
** Either unixShmFile.mutex must be held or unixShmFile.nRef==0 and ** Either unixShmFile.mutex must be held or unixShmFile.nRef==0 and
** unixMutexHeld() is true when reading or writing any other field ** unixMutexHeld() is true when reading or writing any other field
** in this structure. ** in this structure.
**
** To avoid deadlocks, mutex and mutexBuf are always released in the
** reverse order that they are acquired. mutexBuf is always acquired
** first and released last. This invariant is check by asserting
** sqlite3_mutex_notheld() on mutex whenever mutexBuf is acquired or
** released.
*/ */
struct unixShmFile { struct unixShmFile {
struct unixFileId fid; /* Unique file identifier */ struct unixFileId fid; /* Unique file identifier */
@@ -5146,6 +5152,7 @@ static int unixShmGet(
int rc = SQLITE_OK; int rc = SQLITE_OK;
if( p->lockState!=SQLITE_SHM_CHECKPOINT && p->hasMutexBuf==0 ){ if( p->lockState!=SQLITE_SHM_CHECKPOINT && p->hasMutexBuf==0 ){
assert( sqlite3_mutex_notheld(pFile->mutex) );
sqlite3_mutex_enter(pFile->mutexBuf); sqlite3_mutex_enter(pFile->mutexBuf);
p->hasMutexBuf = 1; p->hasMutexBuf = 1;
} }
@@ -5184,6 +5191,7 @@ static int unixShmRelease(sqlite3_shm *pSharedMem){
unixShm *p = (unixShm*)pSharedMem; unixShm *p = (unixShm*)pSharedMem;
if( p->hasMutexBuf && p->lockState!=SQLITE_SHM_RECOVER ){ if( p->hasMutexBuf && p->lockState!=SQLITE_SHM_RECOVER ){
unixShmFile *pFile = p->pFile; unixShmFile *pFile = p->pFile;
assert( sqlite3_mutex_notheld(pFile->mutex) );
sqlite3_mutex_leave(pFile->mutexBuf); sqlite3_mutex_leave(pFile->mutexBuf);
p->hasMutexBuf = 0; p->hasMutexBuf = 0;
} }
@@ -5246,6 +5254,7 @@ static int unixShmLock(
p->id, getpid(), azLkName[p->lockState], azLkName[desiredLock])); p->id, getpid(), azLkName[p->lockState], azLkName[desiredLock]));
if( desiredLock==SQLITE_SHM_RECOVER && !p->hasMutexBuf ){ if( desiredLock==SQLITE_SHM_RECOVER && !p->hasMutexBuf ){
assert( sqlite3_mutex_notheld(pFile->mutex) );
sqlite3_mutex_enter(pFile->mutexBuf); sqlite3_mutex_enter(pFile->mutexBuf);
p->hasMutexBuf = 1; p->hasMutexBuf = 1;
} }