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Fix a race condition in OP_ParseSchema.

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FossilOrigin-Name: 71a799b02a3b3cf2e12758dea29fd2465bbec3e1
This commit is contained in:
dan 2011-04-02 09:44:43 +00:00
parent 82346d9873
commit 6c15487b7e
3 changed files with 24 additions and 21 deletions
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12
manifest
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@ -1,5 +1,5 @@
C Do\snot\sattempt\sto\srun\stests\sthat\suse\sthe\s'wholenumber'\svirtual\stable\sif\sthe\sbuild\sdoes\snot\ssupport\svirtual\stables.
D 2011-04-02T09:25:14.909
C Fix\sa\srace\scondition\sin\sOP_ParseSchema.
D 2011-04-02T09:44:43
F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
F Makefile.in 7a4d9524721d40ef9ee26f93f9bd6a51dba106f2
F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@ -235,7 +235,7 @@ F src/update.c 81911be16ece3c3e7716aa18565b4814ec41f8b9
F src/utf.c d83650c3ea08f7407bd9d0839d9885241c209c60
F src/util.c cd997077bad039efc0597eb027c929658f93c018
F src/vacuum.c 924bd1bcee2dfb05376f79845bd3b4cec7b54b2f
F src/vdbe.c e3f37ca0afdd72e883475e2a32a06167df2810d0
F src/vdbe.c a45a6a0daf2161797d50b3b5b8a3e0e4debf2d2b
F src/vdbe.h 4de0efb4b0fdaaa900cf419b35c458933ef1c6d2
F src/vdbeInt.h e1c6254641168507d25b46affb6dfb53c782f553
F src/vdbeapi.c a09ad9164cafc505250d5dd6b69660c960f1308c
@ -926,7 +926,7 @@ F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
F tool/split-sqlite3c.tcl d9be87f1c340285a3e081eb19b4a247981ed290c
F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
P 139bc5655ed1d0fd1b7ca86d05a998fcc5fbc18e
R 85c1ab3db7c73393d878faa825bb79d8
P 20afd81a4cf4d23962ec841bbd375f36a5156fb6
R 25d34b3e2efbdd1c8e0ceadec6512306
U dan
Z 27401d3cc561174a4c3aaa99ccf5b680
Z 659aea6fa897bf521b0a686e5d197299

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20afd81a4cf4d23962ec841bbd375f36a5156fb6
71a799b02a3b3cf2e12758dea29fd2465bbec3e1

31
src/vdbe.c
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@ -4625,23 +4625,26 @@ case OP_ParseSchema: {
iDb = pOp->p1;
assert( iDb>=0 && iDb<db->nDb );
/* Although the mutex on the BtShared object that corresponds to
** database iDb (the database containing the sqlite_master table
** read by this instruction) is currently held, it is necessary to
** obtain the mutexes on all attached databases before checking if
** the schema of iDb is loaded. This is because, at the start of
** the sqlite3_exec() call below, SQLite will invoke
** sqlite3BtreeEnterAll(). If all mutexes are not already held, the
** iDb mutex may be temporarily released to avoid deadlock. If
** this happens, then some other thread may delete the in-memory
** schema of database iDb before the SQL statement runs. The schema
** will not be reloaded becuase the db->init.busy flag is set. This
** can result in a "no such table: sqlite_master" or "malformed
** database schema" error being returned to the user.
/* When this opcode is invoked, it is guaranteed that the b-tree mutex
** is held and the schema is loaded for database iDb. However, at the
** start of the sqlite3_exec() call below, SQLite will invoke
** sqlite3BtreeEnterAll(). If all mutexes are not already held, the iDb
** mutex may be temporarily released to avoid deadlock. If this happens,
** then some other thread may delete the in-memory schema of database iDb
** before the SQL statement runs. The schema will not be reloaded because
** the db->init.busy flag is set. This can result in a "no such table:
** sqlite_master" or "malformed database schema" error being returned to
** the user.
**
** To avoid this, obtain all mutexes and check that no other thread has
** deleted the schema before calling sqlite3_exec(). If we find that the
** another thread has deleted the schema, there is no need to update it.
** The updated schema will be loaded from disk when it is next required.
*/
assert( sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );
assert( DbHasProperty(db, iDb, DB_SchemaLoaded) );
sqlite3BtreeEnterAll(db);
if( ALWAYS(DbHasProperty(db, iDb, DB_SchemaLoaded)) ){
if( DbHasProperty(db, iDb, DB_SchemaLoaded) ){
zMaster = SCHEMA_TABLE(iDb);
initData.db = db;
initData.iDb = pOp->p1;