June 2018 - openSUSE Programming - openSUSE Mailing Lists

[opensuse-programming] inter-system message queueing ?
by Per Jessen 29 Jun '18

29 Jun '18

Anyone here using zeromq ? I'm looking for a simple inter-system (ie. networked) message queueing library. I only need push-pull, bidirectional. Sofar I've just used my own, but now I need to control the length of a queue. I.e. "don't push unless queuelen<N". I've just now looked at zeromq and rabbitmq, but they both seem a bit too much for what I need. -- Per Jessen, Zürich (19.2°C) http://www.hostsuisse.com/ - virtual servers, made in Switzerland. -- To unsubscribe, e-mail: opensuse-programming+unsubscribe(a)opensuse.org To contact the owner, e-mail: opensuse-programming+owner(a)opensuse.org

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[opensuse-programming] struct aiocb * const* restrict
by Per Jessen 15 Jun '18

15 Jun '18

I'm rebuilding from some code I wrote in 2010 and compiled with gcc 4.2.1. Compiling now with gcc 7.3.1 I get e.g. this warning: /usr/include/aio.h:149:12: note: expected ‘struct aiocb * const* restrict’ but argument is of type ‘struct aiocb *’ afaict, this about what the compiler is allowed to optimize and what not, can anyone elaborate ? -- Per Jessen, Zürich (17.2°C) http://www.dns24.ch/ - your free DNS host, made in Switzerland. -- To unsubscribe, e-mail: opensuse-programming+unsubscribe(a)opensuse.org To contact the owner, e-mail: opensuse-programming+owner(a)opensuse.org

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Re: [opensuse-programming] pthread_mutex vs semaphore.h ?
by Per Jessen 04 Jun '18

04 Jun '18

Roger Oberholtzer wrote: > On Mon, Jun 4, 2018 at 8:45 AM, Per Jessen <per(a)computer.org > <mailto:per@computer.org>> wrote: > > I'm reviving some old code, dates back to 2010. In one place I see I > have replaced use of pthread_mutexes with sem_wait() and sem_post() > (posix semaphores). I just can't see why I did it. :-( > > The semantics are slightly different, but can anyone suggest why one > should use one over the other? (or vice versa). > > > They would act differently. The pthread_mutexes typically wait for > access to a variable. They do not wait for the variable itself to > change. The sem_wait(), well, waits for the semaphore to change. Is the > semaphore value itself the one you are interested in? Or does it's > change mean that some variable you are interested in has changed? IMHO, > pthread_mutexes are safer because when you access the protected > variable, it should not be in the process of changing. Thanks for your input, Roger. Here is what I wrote - //pthread_mutex_lock( &mux ); while( EINTR==sem_wait( &mux ) ); do some queue manip. //pthread_mutex_unlock( &mux ); sem_post( &mux ); mux is either a pthread_mutex_t or a sem_t. The queue manipulation is key, the mux is uninteresting. The reason I am looking at this is that a thread got hung up (over the weekend) - in the core dump, a signal handler was called and tried to write to the queue whilst someone was reading from the queue. It's possible that is why I had to move to using semaphores - I wonder if pthread_mutex_lock is async-safe. /Per -- To unsubscribe, e-mail: opensuse-programming+unsubscribe(a)opensuse.org To contact the owner, e-mail: opensuse-programming+owner(a)opensuse.org

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[opensuse-programming] pthread_mutex vs semaphore.h ?
by Per Jessen 04 Jun '18

04 Jun '18

I'm reviving some old code, dates back to 2010. In one place I see I have replaced use of pthread_mutexes with sem_wait() and sem_post() (posix semaphores). I just can't see why I did it. :-( The semantics are slightly different, but can anyone suggest why one should use one over the other? (or vice versa). -- Per Jessen, Zürich (18.9°C) http://www.hostsuisse.com/ - dedicated server rental in Switzerland. -- To unsubscribe, e-mail: opensuse-programming+unsubscribe(a)opensuse.org To contact the owner, e-mail: opensuse-programming+owner(a)opensuse.org

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