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authorsthen <sthen@openbsd.org>2016-09-23 09:21:58 +0000
committersthen <sthen@openbsd.org>2016-09-23 09:21:58 +0000
commit25e4f8ab5acd0ef40feec6767a572bebbbe294b3 (patch)
tree20197c0e46bb6d260f4a310b6d5dd73b8d826f01 /lib/libsqlite3/src/notify.c
parentremove usr.bin/sqlite3, it has moved back to ports (diff)
downloadwireguard-openbsd-25e4f8ab5acd0ef40feec6767a572bebbbe294b3.tar.xz
wireguard-openbsd-25e4f8ab5acd0ef40feec6767a572bebbbe294b3.zip
remove lib/libsqlite3, it has moved back to ports
Diffstat (limited to 'lib/libsqlite3/src/notify.c')
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diff --git a/lib/libsqlite3/src/notify.c b/lib/libsqlite3/src/notify.c
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-/*
-** 2009 March 3
-**
-** 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 the sqlite3_unlock_notify()
-** API method and its associated functionality.
-*/
-#include "sqliteInt.h"
-#include "btreeInt.h"
-
-/* Omit this entire file if SQLITE_ENABLE_UNLOCK_NOTIFY is not defined. */
-#ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
-
-/*
-** Public interfaces:
-**
-** sqlite3ConnectionBlocked()
-** sqlite3ConnectionUnlocked()
-** sqlite3ConnectionClosed()
-** sqlite3_unlock_notify()
-*/
-
-#define assertMutexHeld() \
- assert( sqlite3_mutex_held(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER)) )
-
-/*
-** Head of a linked list of all sqlite3 objects created by this process
-** for which either sqlite3.pBlockingConnection or sqlite3.pUnlockConnection
-** is not NULL. This variable may only accessed while the STATIC_MASTER
-** mutex is held.
-*/
-static sqlite3 *SQLITE_WSD sqlite3BlockedList = 0;
-
-#ifndef NDEBUG
-/*
-** This function is a complex assert() that verifies the following
-** properties of the blocked connections list:
-**
-** 1) Each entry in the list has a non-NULL value for either
-** pUnlockConnection or pBlockingConnection, or both.
-**
-** 2) All entries in the list that share a common value for
-** xUnlockNotify are grouped together.
-**
-** 3) If the argument db is not NULL, then none of the entries in the
-** blocked connections list have pUnlockConnection or pBlockingConnection
-** set to db. This is used when closing connection db.
-*/
-static void checkListProperties(sqlite3 *db){
- sqlite3 *p;
- for(p=sqlite3BlockedList; p; p=p->pNextBlocked){
- int seen = 0;
- sqlite3 *p2;
-
- /* Verify property (1) */
- assert( p->pUnlockConnection || p->pBlockingConnection );
-
- /* Verify property (2) */
- for(p2=sqlite3BlockedList; p2!=p; p2=p2->pNextBlocked){
- if( p2->xUnlockNotify==p->xUnlockNotify ) seen = 1;
- assert( p2->xUnlockNotify==p->xUnlockNotify || !seen );
- assert( db==0 || p->pUnlockConnection!=db );
- assert( db==0 || p->pBlockingConnection!=db );
- }
- }
-}
-#else
-# define checkListProperties(x)
-#endif
-
-/*
-** Remove connection db from the blocked connections list. If connection
-** db is not currently a part of the list, this function is a no-op.
-*/
-static void removeFromBlockedList(sqlite3 *db){
- sqlite3 **pp;
- assertMutexHeld();
- for(pp=&sqlite3BlockedList; *pp; pp = &(*pp)->pNextBlocked){
- if( *pp==db ){
- *pp = (*pp)->pNextBlocked;
- break;
- }
- }
-}
-
-/*
-** Add connection db to the blocked connections list. It is assumed
-** that it is not already a part of the list.
-*/
-static void addToBlockedList(sqlite3 *db){
- sqlite3 **pp;
- assertMutexHeld();
- for(
- pp=&sqlite3BlockedList;
- *pp && (*pp)->xUnlockNotify!=db->xUnlockNotify;
- pp=&(*pp)->pNextBlocked
- );
- db->pNextBlocked = *pp;
- *pp = db;
-}
-
-/*
-** Obtain the STATIC_MASTER mutex.
-*/
-static void enterMutex(void){
- sqlite3_mutex_enter(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
- checkListProperties(0);
-}
-
-/*
-** Release the STATIC_MASTER mutex.
-*/
-static void leaveMutex(void){
- assertMutexHeld();
- checkListProperties(0);
- sqlite3_mutex_leave(sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_MASTER));
-}
-
-/*
-** Register an unlock-notify callback.
-**
-** This is called after connection "db" has attempted some operation
-** but has received an SQLITE_LOCKED error because another connection
-** (call it pOther) in the same process was busy using the same shared
-** cache. pOther is found by looking at db->pBlockingConnection.
-**
-** If there is no blocking connection, the callback is invoked immediately,
-** before this routine returns.
-**
-** If pOther is already blocked on db, then report SQLITE_LOCKED, to indicate
-** a deadlock.
-**
-** Otherwise, make arrangements to invoke xNotify when pOther drops
-** its locks.
-**
-** Each call to this routine overrides any prior callbacks registered
-** on the same "db". If xNotify==0 then any prior callbacks are immediately
-** cancelled.
-*/
-int sqlite3_unlock_notify(
- sqlite3 *db,
- void (*xNotify)(void **, int),
- void *pArg
-){
- int rc = SQLITE_OK;
-
- sqlite3_mutex_enter(db->mutex);
- enterMutex();
-
- if( xNotify==0 ){
- removeFromBlockedList(db);
- db->pBlockingConnection = 0;
- db->pUnlockConnection = 0;
- db->xUnlockNotify = 0;
- db->pUnlockArg = 0;
- }else if( 0==db->pBlockingConnection ){
- /* The blocking transaction has been concluded. Or there never was a
- ** blocking transaction. In either case, invoke the notify callback
- ** immediately.
- */
- xNotify(&pArg, 1);
- }else{
- sqlite3 *p;
-
- for(p=db->pBlockingConnection; p && p!=db; p=p->pUnlockConnection){}
- if( p ){
- rc = SQLITE_LOCKED; /* Deadlock detected. */
- }else{
- db->pUnlockConnection = db->pBlockingConnection;
- db->xUnlockNotify = xNotify;
- db->pUnlockArg = pArg;
- removeFromBlockedList(db);
- addToBlockedList(db);
- }
- }
-
- leaveMutex();
- assert( !db->mallocFailed );
- sqlite3ErrorWithMsg(db, rc, (rc?"database is deadlocked":0));
- sqlite3_mutex_leave(db->mutex);
- return rc;
-}
-
-/*
-** This function is called while stepping or preparing a statement
-** associated with connection db. The operation will return SQLITE_LOCKED
-** to the user because it requires a lock that will not be available
-** until connection pBlocker concludes its current transaction.
-*/
-void sqlite3ConnectionBlocked(sqlite3 *db, sqlite3 *pBlocker){
- enterMutex();
- if( db->pBlockingConnection==0 && db->pUnlockConnection==0 ){
- addToBlockedList(db);
- }
- db->pBlockingConnection = pBlocker;
- leaveMutex();
-}
-
-/*
-** This function is called when
-** the transaction opened by database db has just finished. Locks held
-** by database connection db have been released.
-**
-** This function loops through each entry in the blocked connections
-** list and does the following:
-**
-** 1) If the sqlite3.pBlockingConnection member of a list entry is
-** set to db, then set pBlockingConnection=0.
-**
-** 2) If the sqlite3.pUnlockConnection member of a list entry is
-** set to db, then invoke the configured unlock-notify callback and
-** set pUnlockConnection=0.
-**
-** 3) If the two steps above mean that pBlockingConnection==0 and
-** pUnlockConnection==0, remove the entry from the blocked connections
-** list.
-*/
-void sqlite3ConnectionUnlocked(sqlite3 *db){
- void (*xUnlockNotify)(void **, int) = 0; /* Unlock-notify cb to invoke */
- int nArg = 0; /* Number of entries in aArg[] */
- sqlite3 **pp; /* Iterator variable */
- void **aArg; /* Arguments to the unlock callback */
- void **aDyn = 0; /* Dynamically allocated space for aArg[] */
- void *aStatic[16]; /* Starter space for aArg[]. No malloc required */
-
- aArg = aStatic;
- enterMutex(); /* Enter STATIC_MASTER mutex */
-
- /* This loop runs once for each entry in the blocked-connections list. */
- for(pp=&sqlite3BlockedList; *pp; /* no-op */ ){
- sqlite3 *p = *pp;
-
- /* Step 1. */
- if( p->pBlockingConnection==db ){
- p->pBlockingConnection = 0;
- }
-
- /* Step 2. */
- if( p->pUnlockConnection==db ){
- assert( p->xUnlockNotify );
- if( p->xUnlockNotify!=xUnlockNotify && nArg!=0 ){
- xUnlockNotify(aArg, nArg);
- nArg = 0;
- }
-
- sqlite3BeginBenignMalloc();
- assert( aArg==aDyn || (aDyn==0 && aArg==aStatic) );
- assert( nArg<=(int)ArraySize(aStatic) || aArg==aDyn );
- if( (!aDyn && nArg==(int)ArraySize(aStatic))
- || (aDyn && nArg==(int)(sqlite3MallocSize(aDyn)/sizeof(void*)))
- ){
- /* The aArg[] array needs to grow. */
- void **pNew = (void **)sqlite3Malloc(nArg*sizeof(void *)*2);
- if( pNew ){
- memcpy(pNew, aArg, nArg*sizeof(void *));
- sqlite3_free(aDyn);
- aDyn = aArg = pNew;
- }else{
- /* This occurs when the array of context pointers that need to
- ** be passed to the unlock-notify callback is larger than the
- ** aStatic[] array allocated on the stack and the attempt to
- ** allocate a larger array from the heap has failed.
- **
- ** This is a difficult situation to handle. Returning an error
- ** code to the caller is insufficient, as even if an error code
- ** is returned the transaction on connection db will still be
- ** closed and the unlock-notify callbacks on blocked connections
- ** will go unissued. This might cause the application to wait
- ** indefinitely for an unlock-notify callback that will never
- ** arrive.
- **
- ** Instead, invoke the unlock-notify callback with the context
- ** array already accumulated. We can then clear the array and
- ** begin accumulating any further context pointers without
- ** requiring any dynamic allocation. This is sub-optimal because
- ** it means that instead of one callback with a large array of
- ** context pointers the application will receive two or more
- ** callbacks with smaller arrays of context pointers, which will
- ** reduce the applications ability to prioritize multiple
- ** connections. But it is the best that can be done under the
- ** circumstances.
- */
- xUnlockNotify(aArg, nArg);
- nArg = 0;
- }
- }
- sqlite3EndBenignMalloc();
-
- aArg[nArg++] = p->pUnlockArg;
- xUnlockNotify = p->xUnlockNotify;
- p->pUnlockConnection = 0;
- p->xUnlockNotify = 0;
- p->pUnlockArg = 0;
- }
-
- /* Step 3. */
- if( p->pBlockingConnection==0 && p->pUnlockConnection==0 ){
- /* Remove connection p from the blocked connections list. */
- *pp = p->pNextBlocked;
- p->pNextBlocked = 0;
- }else{
- pp = &p->pNextBlocked;
- }
- }
-
- if( nArg!=0 ){
- xUnlockNotify(aArg, nArg);
- }
- sqlite3_free(aDyn);
- leaveMutex(); /* Leave STATIC_MASTER mutex */
-}
-
-/*
-** This is called when the database connection passed as an argument is
-** being closed. The connection is removed from the blocked list.
-*/
-void sqlite3ConnectionClosed(sqlite3 *db){
- sqlite3ConnectionUnlocked(db);
- enterMutex();
- removeFromBlockedList(db);
- checkListProperties(db);
- leaveMutex();
-}
-#endif