[EMAIL PROTECTED] wrote:
Hi,
I'm in the process of securing the PL/Java signal handling routines.
Since a multi-threaded JVM is running and a signal can occur
at any time in any thread, I need to trap some of them and
make sure that they are executed in the main thread. Using
Posix signals, this is easy. Here's a sample handler:
static void pljavaStatementCancelHandler(int signum) {
if(pthread_self() == mainThread)
/*
* Call original handler
*/
StatementCancelHandler(signum);
else
/*
* Dispatch to main thread.
*/
pthread_kill(mainThread, signum); /* Send it to main
thread */ }
The mainThread was initialized when the handler was first registered.
From looking at the PostgreSQL signal handling routines for
Win32, I realize that several threads are involved already.
Perhaps all signals are indeed dispatched to the main thread
already? I couldn't really figure it out. I need help from
someone who knows more about this.
The win32 system itself doesn't have the concept of signals. Therefor,
the only signals being delivered are those delivered internally between
the postgresql processes (including those sent manually through pg_ctl).
These "fake signals" are dispatched on the main thread. They are
received by a worker thread, which will queue them up and set a flag,
and the main thread then polls this queue and delivers the actual
signal.
I have *no idea* how pthreads does this. pthread_kill() probably does
not know about *our* signal emulation layer, but somehow has it's own.
(as pthreads definitly aren't used in the backend, but I assume you're
somehow using them for pl/java anyway). Or perhaps that's just not
necessary and the example was for unix only?
Yes, the example is for Posix compliant systems only and it assumes that
the JVM itself base its threading on pthreads.
How is a PostgreSQL process terminated on Windows? Or rather, how is the
concept of die() and quickdie() implemented if it's not based on signals?
Regards,
Thomas Hallgren
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