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
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);
}
}
Cheers,
Kyle Moffett
--
There is no way to make Linux robust with unreliable memory
subsystems, sorry. It would be like trying to make a human more
robust with an unreliable O2 supply. Memory just has to work.
-- Andi Kleen
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
|
|