And those mutexes around statement usage apply the mutex based on the underlying connection, not the statement (which is irrelevant)?
--- Theory is when you know everything but nothing works. Practice is when everything works but no one knows why. Sometimes theory and practice are combined: nothing works and no one knows why. >-----Original Message----- >From: [email protected] [mailto:sqlite-users- >[email protected]] On Behalf Of Neo Anderson >Sent: Sunday, 8 February, 2015 22:34 >To: General Discussion of SQLite Database >Subject: Re: [sqlite] Multi-thread mode question > >> Does the application work if you configure SQLite to serialized mode? >Yes. But I am confused why serialized mode works while multi-thread mode >always cause crashes because I also wrap calls around statement handle. > >> even if you wrap the sqlite3_ calls... you'll need to wrap the entire >> lifetime of the statment... >Do I need to do this in serialized mode (suppose I use a single >connection across multiple threads)? > >---------------------------------------- >> Date: Sun, 8 Feb 2015 03:31:46 -0800 >> From: [email protected] >> To: [email protected] >> Subject: Re: [sqlite] Multi-thread mode question >> >> it's better to use a connection per thread... the connection resource >isn't >> very big... >> even if you wrap the sqlite3_ calls... you'll need to wrap the entire >> lifetime of the statment... if you do a execute and then start stepping >and >> getting values while another thread starts another statement... that's >3 >> individual locks, but it doesn't lock the context of the statement >being >> used... it will lead to bizarre crashes in the database; similar to >> double-releasing memory or delayed reference of memory that has been >> released. >> >> On Sun, Feb 8, 2015 at 3:00 AM, Dan Kennedy <[email protected]> >wrote: >> >>> On 02/08/2015 04:30 PM, Neo Anderson wrote: >>> >>>> The doc says: >>>> >>>> Multi-thread. >>>> In this mode, SQLite can be safely used by multiple threads provided >that >>>> no single database connection is used simultaneously in two or more >>>> threads. >>>> >>>> I have a scenario that every sqlite3_calls around a single database >>>> connection is protected by a recursive mutex, but I have very strange >>>> runtime error in sqlite3.c and each time the error occurs at a >different >>>> place. >>>> >>>> Does this mean the following statement is true: >>>> >>>> In muti-thead mode, a single database connection cannot be shared >among >>>> threads even if any activity around the connection is protected by a >mutex. >>>> >>> >>> Not true. >>> >>> The only difference between multi-threaded and serialized mode is >that, >>> internally, every sqlite3_xxx() API call grabs a recursive mutex to >prevent >>> two threads from simultaneously accessing the database handle >structure. >>> i.e. the same thing your code is doing externally. >>> >>> Note that calls on statement handles (i.e. sqlite3_step(), >>> sqlite3_column_text() etc.) count as calls on the database handle that >>> created them. So you need to protect them with the same mutex. >>> >>> Does the application work if you configure SQLite to serialized mode? >>> >>> Dan. >>> >>> >>> >>> _______________________________________________ >>> sqlite-users mailing list >>> [email protected] >>> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >>> >> _______________________________________________ >> sqlite-users mailing list >> [email protected] >> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > >_______________________________________________ >sqlite-users mailing list >[email protected] >http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
