/*
** 2007 September 9
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains the implementation of some Tcl commands used to
** test that sqlite3 database handles may be concurrently accessed by
** multiple threads. Right now this only works on unix.
*/
#include "sqliteInt.h"
#include <tcl.h>
#if SQLITE_THREADSAFE
#include <errno.h>
#if !defined(_MSC_VER)
#include <unistd.h>
#endif
/*
** One of these is allocated for each thread created by [sqlthread spawn].
*/
typedef struct SqlThread SqlThread;
struct SqlThread {
Tcl_ThreadId parent; /* Thread id of parent thread */
Tcl_Interp *interp; /* Parent interpreter */
char *zScript; /* The script to execute. */
char *zVarname; /* Varname in parent script */
};
/*
** A custom Tcl_Event type used by this module. When the event is
** handled, script zScript is evaluated in interpreter interp. If
** the evaluation throws an exception (returns TCL_ERROR), then the
** error is handled by Tcl_BackgroundError(). If no error occurs,
** the result is simply discarded.
*/
typedef struct EvalEvent EvalEvent;
struct EvalEvent {
Tcl_Event base; /* Base class of type Tcl_Event */
char *zScript; /* The script to execute. */
Tcl_Interp *interp; /* The interpreter to execute it in. */
};
static Tcl_ObjCmdProc sqlthread_proc;
static Tcl_ObjCmdProc clock_seconds_proc;
#if defined(SQLITE_OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
static Tcl_ObjCmdProc blocking_step_proc;
static Tcl_ObjCmdProc blocking_prepare_v2_proc;
#endif
int Sqlitetest1_Init(Tcl_Interp *);
int Sqlite3_Init(Tcl_Interp *);
/* Functions from test1.c */
void *sqlite3TestTextToPtr(const char *);
const char *sqlite3TestErrorName(int);
int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
int sqlite3TestMakePointerStr(Tcl_Interp *, char *, void *);
int sqlite3TestErrCode(Tcl_Interp *, sqlite3 *, int);
/*
** Handler for events of type EvalEvent.
*/
static int tclScriptEvent(Tcl_Event *evPtr, int flags){
int rc;
EvalEvent *p = (EvalEvent *)evPtr;
rc = Tcl_Eval(p->interp, p->zScript);
if( rc!=TCL_OK ){
Tcl_BackgroundError(p->interp);
}
UNUSED_PARAMETER(flags);
return 1;
}
/*
** Register an EvalEvent to evaluate the script pScript in the
** parent interpreter/thread of SqlThread p.
*/
static void postToParent(SqlThread *p, Tcl_Obj *pScript){
EvalEvent *pEvent;
char *zMsg;
int nMsg;
zMsg = Tcl_GetStringFromObj(pScript, &nMsg);
pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
pEvent->base.nextPtr = 0;
pEvent->base.proc = tclScriptEvent;
pEvent->zScript = (char *)&pEvent[1];
memcpy(pEvent->zScript, zMsg, nMsg+1);
pEvent->interp = p->interp;
Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
Tcl_ThreadAlert(p->parent);
}
/*
** The main function for threads created with [sqlthread spawn].
*/
static Tcl_ThreadCreateType tclScriptThread(ClientData pSqlThread){
Tcl_Interp *interp;
Tcl_Obj *pRes;
Tcl_Obj *pList;
int rc;
SqlThread *p = (SqlThread *)pSqlThread;
extern int Sqlitetest_mutex_Init(Tcl_Interp*);
interp = Tcl_CreateInterp();
Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, pSqlThread, 0);
#if defined(SQLITE_OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
Tcl_CreateObjCommand(interp,
"sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc, (void *)1, 0);
Tcl_CreateObjCommand(interp,
"sqlite3_nonblocking_prepare_v2", blocking_prepare_v2_proc, 0, 0);
#endif
Sqlitetest1_Init(interp);
Sqlitetest_mutex_Init(interp);
Sqlite3_Init(interp);
rc = Tcl_Eval(interp, p->zScript);
pRes = Tcl_GetObjResult(interp);
pList = Tcl_NewObj();
Tcl_IncrRefCount(pList);
Tcl_IncrRefCount(pRes);
if( rc!=TCL_OK ){
Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("error", -1));
Tcl_ListObjAppendElement(interp, pList, pRes);
postToParent(p, pList);
Tcl_DecrRefCount(pList);
pList = Tcl_NewObj();
}
Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj("set", -1));
Tcl_ListObjAppendElement(interp, pList, Tcl_NewStringObj(p->zVarname, -1));
Tcl_ListObjAppendElement(interp, pList, pRes);
postToParent(p, pList);
ckfree((void *)p);
Tcl_DecrRefCount(pList);
Tcl_DecrRefCount(pRes);
Tcl_DeleteInterp(interp);
TCL_THREAD_CREATE_RETURN;
}
/*
** sqlthread spawn VARNAME SCRIPT
**
** Spawn a new thread with its own Tcl interpreter and run the
** specified SCRIPT(s) in it. The thread terminates after running
** the script. The result of the script is stored in the variable
** VARNAME.
**
** The caller can wait for the script to terminate using [vwait VARNAME].
*/
static int sqlthread_spawn(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
Tcl_ThreadId x;
SqlThread *pNew;
int rc;
int nVarname; char *zVarname;
int nScript; char *zScript;
/* Parameters for thread creation */
const int nStack = TCL_THREAD_STACK_DEFAULT;
const int flags = TCL_THREAD_NOFLAGS;
assert(objc==4);
UNUSED_PARAMETER(clientData);
UNUSED_PARAMETER(objc);
zVarname = Tcl_GetStringFromObj(objv[2], &nVarname);
zScript = Tcl_GetStringFromObj(objv[3], &nScript);
pNew = (SqlThread *)ckalloc(sizeof(SqlThread)+nVarname+nScript+2);
pNew->zVarname = (char *)&pNew[1];
pNew->zScript = (char *)&pNew->zVarname[nVarname+1];
memcpy(pNew->zVarname, zVarname, nVarname+1);
memcpy(pNew->zScript, zScript, nScript+1);
pNew->parent = Tcl_GetCurrentThread();
pNew->interp = interp;
rc = Tcl_CreateThread(&x, tclScriptThread, (void *)pNew, nStack, flags);
if( rc!=TCL_OK ){
Tcl_AppendResult(interp, "Error in Tcl_CreateThread()", 0);
ckfree((char *)pNew);
return TCL_ERROR;
}
return TCL_OK;
}
/*
** sqlthread parent SCRIPT
**
** This can be called by spawned threads only. It sends the specified
** script back to the parent thread for execution. The result of
** evaluating the SCRIPT is returned. The parent thread must enter
** the event loop for this to work - otherwise the caller will
** block indefinitely.
**
** NOTE: At the moment, this doesn't work. FIXME.
*/
static int sqlthread_parent(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
EvalEvent *pEvent;
char *zMsg;
int nMsg;
SqlThread *p = (SqlThread *)clientData;
assert(objc==3);
UNUSED_PARAMETER(objc);
if( p==0 ){
Tcl_AppendResult(interp, "no parent thread", 0);
return TCL_ERROR;
}
zMsg = Tcl_GetStringFromObj(objv[2], &nMsg);
pEvent = (EvalEvent *)ckalloc(sizeof(EvalEvent)+nMsg+1);
pEvent->base.nextPtr = 0;
pEvent->base.proc = tclScriptEvent;
pEvent->zScript = (char *)&pEvent[1];
memcpy(pEvent->zScript, zMsg, nMsg+1);
pEvent->interp = p->interp;
Tcl_ThreadQueueEvent(p->parent, (Tcl_Event *)pEvent, TCL_QUEUE_TAIL);
Tcl_ThreadAlert(p->parent);
return TCL_OK;
}
static int xBusy(void *pArg, int nBusy){
UNUSED_PARAMETER(pArg);
UNUSED_PARAMETER(nBusy);
sqlite3_sleep(50);
return 1; /* Try again... */
}
/*
** sqlthread open
**
** Open a database handle and return the string representation of
** the pointer value.
*/
static int sqlthread_open(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
int sqlite3TestMakePointerStr(Tcl_Interp *interp, char *zPtr, void *p);
const char *zFilename;
sqlite3 *db;
int rc;
char zBuf[100];
extern void Md5_Register(sqlite3*);
UNUSED_PARAMETER(clientData);
UNUSED_PARAMETER(objc);
zFilename = Tcl_GetString(objv[2]);
rc = sqlite3_open(zFilename, &db);
Md5_Register(db);
sqlite3_busy_handler(db, xBusy, 0);
if( sqlite3TestMakePointerStr(interp, zBuf, db) ) return TCL_ERROR;
Tcl_AppendResult(interp, zBuf, 0);
return TCL_OK;
}
/*
** sqlthread open
**
** Return the current thread-id (Tcl_GetCurrentThread()) cast to
** an integer.
*/
static int sqlthread_id(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
Tcl_ThreadId id = Tcl_GetCurrentThread();
Tcl_SetObjResult(interp, Tcl_NewIntObj((int)id));
UNUSED_PARAMETER(clientData);
UNUSED_PARAMETER(objc);
UNUSED_PARAMETER(objv);
return TCL_OK;
}
/*
** Dispatch routine for the sub-commands of [sqlthread].
*/
static int sqlthread_proc(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
struct SubCommand {
char *zName;
Tcl_ObjCmdProc *xProc;
int nArg;
char *zUsage;
} aSub[] = {
{"parent", sqlthread_parent, 1, "SCRIPT"},
{"spawn", sqlthread_spawn, 2, "VARNAME SCRIPT"},
{"open", sqlthread_open, 1, "DBNAME"},
{"id", sqlthread_id, 0, ""},
{0, 0, 0}
};
struct SubCommand *pSub;
int rc;
int iIndex;
if( objc<2 ){
Tcl_WrongNumArgs(interp, 1, objv, "SUB-COMMAND");
return TCL_ERROR;
}
rc = Tcl_GetIndexFromObjStruct(
interp, objv[1], aSub, sizeof(aSub[0]), "sub-command", 0, &iIndex
);
if( rc!=TCL_OK ) return rc;
pSub = &aSub[iIndex];
if( objc!=(pSub->nArg+2) ){
Tcl_WrongNumArgs(interp, 2, objv, pSub->zUsage);
return TCL_ERROR;
}
return pSub->xProc(clientData, interp, objc, objv);
}
/*
** The [clock_seconds] command. This is more or less the same as the
** regular tcl [clock seconds], except that it is available in testfixture
** when linked against both Tcl 8.4 and 8.5. Because [clock seconds] is
** implemented as a script in Tcl 8.5, it is not usually available to
** testfixture.
*/
static int clock_seconds_proc(
ClientData clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
Tcl_Time now;
Tcl_GetTime(&now);
Tcl_SetObjResult(interp, Tcl_NewIntObj(now.sec));
UNUSED_PARAMETER(clientData);
UNUSED_PARAMETER(objc);
UNUSED_PARAMETER(objv);
return TCL_OK;
}
/*************************************************************************
** This block contains the implementation of the [sqlite3_blocking_step]
** command available to threads created by [sqlthread spawn] commands. It
** is only available on UNIX for now. This is because pthread condition
** variables are used.
**
** The source code for the C functions sqlite3_blocking_step(),
** blocking_step_notify() and the structure UnlockNotification is
** automatically extracted from this file and used as part of the
** documentation for the sqlite3_unlock_notify() API function. This
** should be considered if these functions are to be extended (i.e. to
** support windows) in the future.
*/
#if defined(SQLITE_OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
/* BEGIN_SQLITE_BLOCKING_STEP */
/* This example uses the pthreads API */
#include <pthread.h>
/*
** A pointer to an instance of this structure is passed as the user-context
** pointer when registering for an unlock-notify callback.
*/
typedef struct UnlockNotification UnlockNotification;
struct UnlockNotification {
int fired; /* True after unlock event has occured */
pthread_cond_t cond; /* Condition variable to wait on */
pthread_mutex_t mutex; /* Mutex to protect structure */
};
/*
** This function is an unlock-notify callback registered with SQLite.
*/
static void unlock_notify_cb(void **apArg, int nArg){
int i;
for(i=0; i<nArg; i++){
UnlockNotification *p = (UnlockNotification *)apArg[i];
pthread_mutex_lock(&p->mutex);
p->fired = 1;
pthread_cond_signal(&p->cond);
pthread_mutex_unlock(&p->mutex);
}
}
/*
** This function assumes that an SQLite API call (either sqlite3_prepare_v2()
** or sqlite3_step()) has just returned SQLITE_LOCKED. The argument is the
** associated database connection.
**
** This function calls sqlite3_unlock_notify() to register for an
** unlock-notify callback, then blocks until that callback is delivered
** and returns SQLITE_OK. The caller should then retry the failed operation.
**
** Or, if sqlite3_unlock_notify() indicates that to block would deadlock
** the system, then this function returns SQLITE_LOCKED immediately. In
** this case the caller should not retry the operation and should roll
** back the current transaction (if any).
*/
static int wait_for_unlock_notify(sqlite3 *db){
int rc;
UnlockNotification un;
/* Initialize the UnlockNotification structure. */
un.fired = 0;
pthread_mutex_init(&un.mutex, 0);
pthread_cond_init(&un.cond, 0);
/* Register for an unlock-notify callback. */
rc = sqlite3_unlock_notify(db, unlock_notify_cb, (void *)&un);
assert( rc==SQLITE_LOCKED || rc==SQLITE_OK );
/* The call to sqlite3_unlock_notify() always returns either SQLITE_LOCKED
** or SQLITE_OK.
**
** If SQLITE_LOCKED was returned, then the system is deadlocked. In this
** case this function needs to return SQLITE_LOCKED to the caller so
** that the current transaction can be rolled back. Otherwise, block
** until the unlock-notify callback is invoked, then return SQLITE_OK.
*/
if( rc==SQLITE_OK ){
pthread_mutex_lock(&un.mutex);
if( !un.fired ){
pthread_cond_wait(&un.cond, &un.mutex);
}
pthread_mutex_unlock(&un.mutex);
}
/* Destroy the mutex and condition variables. */
pthread_cond_destroy(&un.cond);
pthread_mutex_destroy(&un.mutex);
return rc;
}
/*
** This function is a wrapper around the SQLite function sqlite3_step().
** It functions in the same way as step(), except that if a required
** shared-cache lock cannot be obtained, this function may block waiting for
** the lock to become available. In this scenario the normal API step()
** function always returns SQLITE_LOCKED.
**
** If this function returns SQLITE_LOCKED, the caller should rollback
** the current transaction (if any) and try again later. Otherwise, the
** system may become deadlocked.
*/
int sqlite3_blocking_step(sqlite3_stmt *pStmt){
int rc;
while( SQLITE_LOCKED==(rc = sqlite3_step(pStmt)) ){
rc = wait_for_unlock_notify(sqlite3_db_handle(pStmt));
if( rc!=SQLITE_OK ) break;
sqlite3_reset(pStmt);
}
return rc;
}
/*
** This function is a wrapper around the SQLite function sqlite3_prepare_v2().
** It functions in the same way as prepare_v2(), except that if a required
** shared-cache lock cannot be obtained, this function may block waiting for
** the lock to become available. In this scenario the normal API prepare_v2()
** function always returns SQLITE_LOCKED.
**
** If this function returns SQLITE_LOCKED, the caller should rollback
** the current transaction (if any) and try again later. Otherwise, the
** system may become deadlocked.
*/
int sqlite3_blocking_prepare_v2(
sqlite3 *db, /* Database handle. */
const char *zSql, /* UTF-8 encoded SQL statement. */
int nSql, /* Length of zSql in bytes. */
sqlite3_stmt **ppStmt, /* OUT: A pointer to the prepared statement */
const char **pz /* OUT: End of parsed string */
){
int rc;
while( SQLITE_LOCKED==(rc = sqlite3_prepare_v2(db, zSql, nSql, ppStmt, pz)) ){
rc = wait_for_unlock_notify(db);
if( rc!=SQLITE_OK ) break;
}
return rc;
}
/* END_SQLITE_BLOCKING_STEP */
/*
** Usage: sqlite3_blocking_step STMT
**
** Advance the statement to the next row.
*/
static int blocking_step_proc(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
sqlite3_stmt *pStmt;
int rc;
if( objc!=2 ){
Tcl_WrongNumArgs(interp, 1, objv, "STMT");
return TCL_ERROR;
}
pStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
rc = sqlite3_blocking_step(pStmt);
Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), 0);
return TCL_OK;
}
/*
** Usage: sqlite3_blocking_prepare_v2 DB sql bytes ?tailvar?
** Usage: sqlite3_nonblocking_prepare_v2 DB sql bytes ?tailvar?
*/
static int blocking_prepare_v2_proc(
void * clientData,
Tcl_Interp *interp,
int objc,
Tcl_Obj *CONST objv[]
){
sqlite3 *db;
const char *zSql;
int bytes;
const char *zTail = 0;
sqlite3_stmt *pStmt = 0;
char zBuf[50];
int rc;
int isBlocking = !(clientData==0);
if( objc!=5 && objc!=4 ){
Tcl_AppendResult(interp, "wrong # args: should be \"",
Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
return TCL_ERROR;
}
if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
zSql = Tcl_GetString(objv[2]);
if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;
if( isBlocking ){
rc = sqlite3_blocking_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
}else{
rc = sqlite3_prepare_v2(db, zSql, bytes, &pStmt, &zTail);
}
assert(rc==SQLITE_OK || pStmt==0);
if( zTail && objc>=5 ){
if( bytes>=0 ){
bytes = bytes - (zTail-zSql);
}
Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
}
if( rc!=SQLITE_OK ){
assert( pStmt==0 );
sprintf(zBuf, "%s ", (char *)sqlite3TestErrorName(rc));
Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
return TCL_ERROR;
}
if( pStmt ){
if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
Tcl_AppendResult(interp, zBuf, 0);
}
return TCL_OK;
}
#endif /* SQLITE_OS_UNIX && SQLITE_ENABLE_UNLOCK_NOTIFY */
/*
** End of implementation of [sqlite3_blocking_step].
************************************************************************/
/*
** Register commands with the TCL interpreter.
*/
int SqlitetestThread_Init(Tcl_Interp *interp){
Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, 0, 0);
Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
#if defined(SQLITE_OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
Tcl_CreateObjCommand(interp,
"sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc, (void *)1, 0);
Tcl_CreateObjCommand(interp,
"sqlite3_nonblocking_prepare_v2", blocking_prepare_v2_proc, 0, 0);
#endif
return TCL_OK;
}
#else
int SqlitetestThread_Init(Tcl_Interp *interp){
return TCL_OK;
}
#endif