Abramo Bagnara wrote: >Takashi Iwai wrote: >> >> it CAN happen if you have multi-threads. >> the problem is that we have no option to block the poll. > >If you have multi-thread you have other alternative to do that. >OTOH application can't detect *why* poll is blocking with the change you >advocate.
as has been said before, it is fairly easy to detect this. and to reiterate, if this happens in a single-threaded app the code is broken by design because it poll()s before starting the pcm. i'm (we're) still waiting for your answers to these arguments. >> but the current behavior is incorrect from the interpretation of >> POSIX. so this must be a bug. >> if we have to change it, then i would choose the new one, because it's >> more intuitive without exception. > >As pointed by Clemens the current is the proper POSIX behaviour. clemens quoted the write(2) behaviour POSIX mandates. this has nothing to do with the poll(2) behaviour. quoting www.opengroup.org/onlinepubs/007904975/functions/poll.html on POSIX-compliant poll events/revents flags: <quote> POLLERR An error has occurred on the device or stream. [...] </quote> which is not the case. in the scenario you describe (a single- threaded app polling before the pcm is started) the error is within the calling code logic, but clearly not 'on the device or stream'. the same document goes on to say: <quote> If none of the defined events have occurred on any selected file descriptor, poll() shall wait at least timeout milliseconds for an event to occur on any of the selected file descriptors. If the value of timeout is 0, poll() shall return immediately. If the value of timeout is -1, poll() shall block until a requested event occurs or until the call is interrupted. </quote> there's nothing in this document that says the poll implementation shall care about whether the condition polled for is likely or unlikely to occur. it must be concluded that the current poll implementation violates the POSIX standard. tim ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
