Messages in this thread | | | Subject | Re: 2.6.14-rc1 wait()/SIG_CHILD bevahiour | From | Badari Pulavarty <> | Date | Mon, 19 Sep 2005 11:19:21 -0700 |
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On Mon, 2005-09-19 at 14:01 -0400, Kyle Moffett wrote: > On Sep 19, 2005, at 13:39:33, Badari Pulavarty wrote: > > Hi, > > > > I am looking at a problem where the parent process doesn't seem to > > cleanup the exited children (with a webserver). We narrowed it down > > to a simple testcase. Seems more like a lost SIG_CHILD. > > You don't get one SIG_CHLD per child that quits. The kernel may and > probably will merge SIG_CHLD signals together if it has several > queued before it gets a chance to deliver them to your process. This > is true of _all_ signals. If you "kill -STOP 1234", then "kill -QUIT > 1234", "kill -QUIT 1234", "kill -QUIT 1234", "kill -CONT 1234", the > PID 1234 will have 3 signals delivered: The original untrappable > SIGSTOP, the SIGCONT that causes it to resume, and a single SIGQUIT
True.
> immediately following it. The correct and portable way to handle > this is to put a loop in your SIGCHLD signal handler: > > #include <sys/types.h> > #include <sys/wait.h> > > void sigchld_handler(int signal) { > pid_t pid; > int status; > > while( -1 != (child = waitpid(-1, &status, WNOHANG)) ) { > /* > * Now "status" is the exit status of the child and > * "pid" is its pid. See the waitpid() manpage for > * macros you can use to get information from the > * status variable. > */ > do_some_processing_of_exited_child(pid,status); > } > }
Thats what I already do, in my current testcase.
while(1) { pid = wait4(-1, &status, WNOHANG, &ru); if (pid <= 0) break; // printf("SIGCHLD received for pid %d\n", pid); pid_exited(pid); }
Thanks, Badari
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