fb_shutdown_callback has no effect when used in a multithreaded environment
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Key: CORE-3635
URL: http://tracker.firebirdsql.org/browse/CORE-3635
Project: Firebird Core
Issue Type: Bug
Components: API / Client Library
Affects Versions: 2.5.0
Environment: Linux Debian-Squeeze libfbclient2 Build 26054
Firebird SS 2.5.0.26054
Application written in C++ is using omniORB for IPC and the POSIX threading
from omniORB
Reporter: Eberhard Leba
The Application using the fbclient library has its own shutdown handler running
in a dedicated thread. Database queries and modifications are done in a
separate worker thread that serializes the requests.
Starting using FB version 2.5.0 the application process has been terminated
ungracefully by the worker thread
* loosing connection to the database (Cursor failed arg:, SQLCODE:-902)
* loosing IPC because omniorb DTOR is called.
After the problem was analyzed a fb_shutdown_callback was implemented, as shown
in the example, but the database connection still gets lost when the value 1 is
returned.
int FB_shutdownCallbackHandler(const int reason, const int mask, void* arg){
log_FUNC_m(FB_shutdownCallback);
int rc = 0;
// Do not terminate on SIGTERM or SIGINT
if (mask == fb_shut_preproviders && reason == fb_shutrsn_signal) {
rc = 1; // do not shut down
g_ShutdownPermitted.Wait();
}
log_DBG_m(dbg_LOW, "***** Reason = " << reason << " mask = 0x" << hex <<
mask << " ***** returning " << rc );
return rc;
}
As a workaround FB_shutdownCallbackHandler is now blocked on a semaphore (the
g_ShutdownPermitted.Wait stuff) until the application shutdown did its work.
In this case the app shuts down as designed, but there is still a race
condition left.
BTW: I have also tried to return 0 from the handler in case of
mask == fb_shut_preproviders && reason == fb_shutrsn_signal
but it does not seem to have an effect either.
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