Messages in this thread | | | Date | Fri, 13 Aug 2004 22:06:04 +0200 | From | Frank van Maarseveen <> | Subject | Re: 2.6.x Fork Problem? |
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On Fri, Aug 13, 2004 at 03:36:34PM -0400, Richard B. Johnson wrote: > > In the above code there is something missing. in the code shown, > the child __will__ wait in exit() until somebody claims its status. > However, the child probably did a setsid(), becoming a process-leader > or the parent set up a SIGCHLD handler before the fork. In these > cases, the exit() will quickly exit because somebody will claim > the exit status. > > So, by the time the parent gets the CPU, the child is long gone. > The solution is to use the default SIGCHLD handler if the parent > expects to get the child's status and for the child to not execute > setsid(), which will allow init to reap its status.
AFAIK a child doing setsid() has no effect whatsoever on any wait*() done by the parent. It just sets a new session leader.
But SIGCHLD set to SIG_IGN instead of SIG_DFL is a perfect explanation. Rereading alan's reply I suddenly got it: "random status" didn't refer to the &status arg but to the signal status. SIG_IGN is inherited I guess so a
signal(SIGCHLD, SIG_DFL);
once before the fork() should fix it. Hmm, so actually our parent should have reset SIGCHLD before exec'ing this code. This could cause more problems.
-- Frank - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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