Xapian discuss - Aug 2010 - thread locked while flushing to database

On a multicore Linux platform I'm running a simple c test program, to
evaluate xapian performance, and inspect advantages in multiple indexing.
I'm starting two threads, and each thread writes to his database.

   main th          -> indexing thread_1 -> db1
(dispatcher)     -> indexing thread_2 -> db2

I use sched_setaffinity to bind each indexing thread to a specific core.

During indexing phase i see both core running, but when my threads try to
flush to the databases one of them keeps working, the other thread stop the
execution (0% cpu) and stracing his pid seems that it's blocked in a futex.

Why does this happens if the 2 databases are different objects (with
different path)?
I'm doing something wrong?
This seem to happen both with xapian-core.1.1.3 and xapian-core.1.2.2, and
different gcc versions.

Here are some details, strace outpud, gdb output, and top results:
http://pastebin.com/udGQTi6K

Cheers.

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Luca Barbieri

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).

The execution doesn't change also without the set_affinity :(
Here there's a semplified exemple of my indexing thread's code:
http://pastebin.com/gy6tJTpr
Does anybody see something irregular?


-- 
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Luca Barbieri