Re: OSDL DBT-2 w/ PostgreSQL 7.3.4 and 7.4beta5

markw(at)osdl(dot)org wrote:

>On 1 Nov, Tom Lane wrote:
>
>
>>Manfred Spraul <manfred(at)colorfullife(dot)com> writes:
>>
>>
>>>signal handlers are a process property, not a thread property - that
>>>code is broken for multi-threaded apps.
>>>
>>>
>>Yeah, that's been mentioned before, but I don't see any way around it.
>>What we really want is to turn off SIGPIPE delivery on our socket
>>(only), but AFAIK there is no API to do that.
>>
>>
>
>Will this be a problem for multi-threaded apps with any of the client
>interfaces?
>
>Anyone working on making it threadsafe?
>
>
The POSIX api is not thread safe: signal handlers are per process, and
libpq would like to block SIGPIPE for it's send() calls. For single
threaded apps, libpq just calls sigaction and sets the handler to
SIG_IGN around the syscalls.
For multithreaded apps, this is not possible: sigaction is per process.
Thus the calling application must handle the SIGPIPE signals for libpq -
either by blocking or ignoring them. We are still discussing the exact
API. Probably a global state that is accessible through a new function.

One thread-safe alternative might be the combination of sigprocmask /
pthread_sigmask and sigwait, but I think this would be too fragile.

--
Manfred