[Xapian-discuss] thread locked while flushing to database

[Olly Betts]

On Thu, Aug 12, 2010 at 10:53:29AM +0100, William Crawford wrote:
> On Thursday 12 August 2010 09:53:42 Luca Barbieri wrote:
> 
> > Here are some details, strace outpud, gdb output, and top results:
> > http://pastebin.com/udGQTi6K
> 
> The output shows the other thread is blocked trying to call a thread library
> function (pthread_setcanceltype) from the bowels of libstdc++. While this
> could be a Xapian bug at heart, it's not obvious without seeing more code
> what could be causing this (it's basically a threading deadlock of some
> sort).

It looks like one thread is calling new and the other delete - I guess in the
libstdc++ allocator there's a lock of some sort.

There's no thread specific code in Xapian (on Linux at least - the remote
backend on Microsoft Windows uses a thread internally for something).  We
take care to avoid global mutable data, and so everything should work if
you don't share objects between threads, or protect accesses with a lock if you
do.

I'm not sure what's going on - all I can really suggest is the usual debugging
technique of trying to simplify the situation.  For example, what happens if
you don't set the thread affinity?

Cheers,
    Olly