On 01/03/2010 16:37, Roger A. Faulkner wrote: > 2. The number of realtime signals (32 or 64) has been vigorous debated. > > I argued that sigqueue() could be used for sending signals with > its additional 'union sigval' argument providing for many more > discriminating values than just the number of realtime signal numbers. > > In support of this position, I found this statement in the latest > Posix standard (IEEE Std 1003.1(tm)-2008): > > Rationale for System Interfaces > > B.2.4.2 Realtime Signal Generation and Delivery > > An application-defined value passed to the signal handler is used > to differentiate between different "events" instead of requiring > that the application use different signal numbers for several reasons: > > - Realtime applications potentially handle a very large number of > different events. Requiring that implementations support a > correspondingly large number of distinct signal numbers will > adversely impact the performance of signal delivery because the > signal masks to be manipulated on entry and exit to the handlers > will become large. > > - Event notifications are prioritized by signal number (the rationale > for this is explained in the following paragraphs) and the use of > different signal numbers to differentiate between the different > event notifications overloads the signal number more than has > already been done. It also requires that the application developer > make arbitrary assignments of priority to events that are logically > of equal priority. > > I stand firm on my proposal to make the number be 32.
With the information in "IEEE Std 1003.1(tm)-2008" I think the proposal is sound to use 32. It provides sufficient "Linux compatibility" and is inline with standards recommendations. -- Darren J Moffat
