Hi Mark, I would like to figure out ways in which libevent can be more thread friendly without requiring everyone to use threads. So, thread specific store for the event base seems like a good idea and I would certainly appreciate to see patches.
Niels. On 8/5/07, Mark Heily <[EMAIL PROTECTED]> wrote: > On Sun, 2007-08-05 at 15:31 -0300, Victor wrote: > > Is it safe to call event_add() from a second thread to > > add more events on that event loop base? > > No. Two threads cannot modify the same event_base struct without > explicit locking. You would need to use a mutex to protect the > event_add() call. > > On a related note... > > I would like to see a threaded version of libevent that would give each > thread it's own current_base variable. Right now, there is a global > variable in event.c: > > struct event_base *current_base = NULL; > > A threaded library would use thread-specific data instead: > > static pthread_key_t *current_base_key; > #define current_base \ > ((struct event_base *) (pthread_get_specific(current_base_key)) > > This would allow you to use event_add(), event_dispatch(), and > event_loop() in multiple threads in a natural way. Each thread would get > it's own event loop automatically and not interfere with other threads' > operation. > > You could also add internal protection within the event_base_() > functions with mutexes so that two threads would not be able to modify > the same event_base struct simultaneously. > > My suggestion is to name this threaded version of the library > `libevent_r.a` and have a separate Makefile target to generate the > threaded version. This second target would add -D_REENTRANT to the > CFLAGS to enable all of the threaded codepaths. You would also need to > link it with the pthreads library by adding -lpthread to the LDFLAGS. > > Returning to my previous example, you would modify event.c to look > something like this: > > #if _REENTRANT > > static pthread_key_t *current_base_key; > # define current_base \ > ((struct event_base *) (pthread_get_specific(current_base_key)) > > #else > > struct event_base *current_base = NULL; > > #endif > > > This approach allows both the threadsafe and non-threadsafe library to > be built from the same source code. > > Niels, does this sound like something you would be willing to consider? > If so, I would be willing to do the work and submit a patch. > > Regards, > > Mark > > > _______________________________________________ > Libevent-users mailing list > Libevent-users@monkey.org > http://monkey.org/mailman/listinfo/libevent-users > > _______________________________________________ Libevent-users mailing list Libevent-users@monkey.org http://monkey.org/mailman/listinfo/libevent-users
