Hi Sebastian, On Sun, Jan 18, 2009 at 3:02 AM, Sebastian Kienzl <seb@xxxxxxxx> wrote: > Hello! > > There's a bug in the select_tut man-page in the chapter "Combining Signal > and Data Events", which should illustrate pselect()-usage. > > See the attachments for detailed information, proof-code and a proposed fix. > > Regards, > Seb. > > /* > This is a demonstration of how the code provided > in the Linux man-page select_tut(2) / "Combining Signal and Data Events" > for counting SIGCHLD-events is not correct. > > The problem is that the example-code assumes that > normal signals get queued somehow, which is not the case; quote from > signal(7): > > "By contrast, if multiple instances of a standard signal are delivered > while that signal is currently blocked, then only one instance is queued." > > Bottom line: > > Setting a global flag when a signal has occured will do the job > and that's what pselect() is intended for -- but counting the occurences > of a standard signal as shown in the example DOES NOT WORK. Thanks for your very thorough report. I agree that the example in its current form seems to be confused. (And indeed, there are many things taht I do not really like about this page, and I plan to clean some of them up.) > Compile and run this file to see how the example code will result in zombies > if multiple SIGCHLDs are delivered at the same time; > compile with -DCORRECT to get the correct solution for this case. > > See select_tut-badcount-fix.patch for a proposal to fix the documentation,. However, what I am inclined to do is fix the program, rather than the text. I will send you a revised version in a moment; please take a look at it. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
