Avoid a race condition that might cause a busy_timeout to last longer than

it should.

FossilOrigin-Name: b81960561b47a1b49646f2f8870dd0684dc4ca7c0b9e11076fd713de66b75972

4 files changed, 24 insertions, 7 deletions

diff --git a/src/btree.c b/src/btree.c
index 6bcf379d6..402503916 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -3373,6 +3373,7 @@ int sqlite3BtreeBeginTrans(Btree *p, int wrflag){
     }
   }while( (rc&0xFF)==SQLITE_BUSY && pBt->inTransaction==TRANS_NONE &&
           btreeInvokeBusyHandler(pBt) );
+  sqlite3PagerResetLockTimeout(pBt->pPager);
 
   if( rc==SQLITE_OK ){
     if( p->inTrans==TRANS_NONE ){
diff --git a/src/os_unix.c b/src/os_unix.c
index ac4ec2f2f..2b9c117e3 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -1490,18 +1490,15 @@ static int osSetPosixAdvisoryLock(
   unixFile *pFile       /* Structure holding timeout value */
 ){
   int rc = osFcntl(h,F_SETLK,pLock);
-  if( rc<0 && pFile->iBusyTimeout>0 ){
+  while( rc<0 && pFile->iBusyTimeout>0 ){
     /* On systems that support some kind of blocking file lock with a timeout,
     ** make appropriate changes here to invoke that blocking file lock.  On
     ** generic posix, however, there is no such API.  So we simply try the
     ** lock once every millisecond until either the timeout expires, or until
     ** the lock is obtained. */
-    do{
-      usleep(1000);
-      rc = osFcntl(h,F_SETLK,pLock);
-      pFile->iBusyTimeout--;
-    }while( rc<0 && pFile->iBusyTimeout>0 );
-    pFile->iBusyTimeout = 0;
+    usleep(1000);
+    rc = osFcntl(h,F_SETLK,pLock);
+    pFile->iBusyTimeout--;
   }
   return rc;
 }
diff --git a/src/pager.c b/src/pager.c
index 55f90057e..85d1845e9 100644
--- a/src/pager.c
+++ b/src/pager.c
@@ -5693,6 +5693,7 @@ void sqlite3PagerUnrefPageOne(DbPage *pPg){
   assert( pPg->pgno==1 );
   assert( (pPg->flags & PGHDR_MMAP)==0 ); /* Page1 is never memory mapped */
   pPager = pPg->pPager;
+  sqlite3PagerResetLockTimeout(pPager);
   sqlite3PcacheRelease(pPg);
   pagerUnlockIfUnused(pPager);
 }
@@ -6970,6 +6971,18 @@ sqlite3_file *sqlite3PagerFile(Pager *pPager){
   return pPager->fd;
 }
 
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+/*
+** Reset the lock timeout for pager.
+*/
+void sqlite3PagerResetLockTimeout(Pager *pPager){
+  if( isOpen(pPager->fd) ){
+    int x = 0;
+    sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_LOCK_TIMEOUT, &x);
+  }
+}
+#endif
+
 /*
 ** Return the file handle for the journal file (if it exists).
 ** This will be either the rollback journal or the WAL file.
@@ -7430,6 +7443,7 @@ int sqlite3PagerCheckpoint(
         pPager->walSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
         pnLog, pnCkpt
     );
+    sqlite3PagerResetLockTimeout(pPager);
   }
   return rc;
 }
diff --git a/src/pager.h b/src/pager.h
index 48bc80df1..730e366fb 100644
--- a/src/pager.h
+++ b/src/pager.h
@@ -212,6 +212,11 @@ int sqlite3PagerIsMemdb(Pager*);
 void sqlite3PagerCacheStat(Pager *, int, int, int *);
 void sqlite3PagerClearCache(Pager*);
 int sqlite3SectorSize(sqlite3_file *);
+#ifdef SQLITE_ENABLE_SETLK_TIMEOUT
+void sqlite3PagerResetLockTimeout(Pager *pPager);
+#else
+# define sqlite3PagerResetLockTimeout(X)
+#endif
 
 /* Functions used to truncate the database file. */
 void sqlite3PagerTruncateImage(Pager*,Pgno);