Re: select/poll bug?

[christos%zoulas.com@localhost (Christos Zoulas)]

On Aug 2,  4:12pm, roy%marples.name@localhost (Roy Marples) wrote:
-- Subject: Re: select/poll bug?

| On Sat, 2008-08-02 at 14:26 +0000, Christos Zoulas wrote:
| > On NetBSD you should use pollts(2) I think.
| 
| pselect is more portable I would guess, but platforms like OpenBSD lack
| either. I could trivially add a pselect wrapper for systems that lack
| it. But would pselect avoid the need to artifically reduce my timers on
| ALL platforms?
| 
| I'll test it :)

The select family of system calls is generally inferior to poll because:

1. Expensive because you need do operations on bitmasks [ffs/shifts].
2. Expensive because you need to reset the masks before each call.
3. Non portable behavior for >= 256 fd's. All systems need source
   recompilation; some older systems need kernel recompilation.
4. Non-portable behavior with respect to ERESTART.
5. Non-portable behavior when running out of resources. The only
   way to fix this is using non-blocking-io which is a bit of a pain.
6. Non-portable behavior with respect to "struct timeval *timeout".
   This is non-const, and it was originally intended to return
   the time left. Most implementations did not change "timeout", but  
   one or two did, so it is always good to re-initialize "timeout".  
7. Can only report 3 types of events, read/write/except.

christos