On Wed, 23 Sep 2015 17:20:50 -0400
Steve Dickson <steved@xxxxxxxxxx> wrote:
> Instead of waiting on every fork, which would
> become a bottle neck during a mount storm, simply
> set a SIGCHLD signal handler to do the wait on
> the child process
>
> Signed-off-by: Steve Dickson <steved@xxxxxxxxxx>
> ---
> utils/gssd/gssd.c | 18 ++++++++++++++++++
> utils/gssd/gssd_proc.c | 11 ++---------
> 2 files changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
> index e480349..8b778cb 100644
> --- a/utils/gssd/gssd.c
> +++ b/utils/gssd/gssd.c
> @@ -44,11 +44,13 @@
> #define _GNU_SOURCE
> #endif
>
> +#include <sys/types.h>
> #include <sys/param.h>
> #include <sys/socket.h>
> #include <sys/time.h>
> #include <sys/resource.h>
> #include <sys/inotify.h>
> +#include <sys/wait.h>
> #include <rpc/rpc.h>
> #include <netinet/in.h>
> #include <arpa/inet.h>
> @@ -736,6 +738,21 @@ sig_die(int signal)
> printerr(1, "exiting on signal %d\n", signal);
> exit(0);
> }
> +static void
> +sig_child(int signal)
> +{
> + int err;
> + pid_t pid;
> +
> + /* Parent: just wait on child to exit and return */
> + do {
> + pid = wait(&err);
> + } while(pid == -1 && errno != -ECHILD);
> +
> + if (WIFSIGNALED(err))
> + printerr(0, "WARNING: forked child was killed"
> + "with signal %d\n", WTERMSIG(err));
> +}
>
> static void
> usage(char *progname)
> @@ -902,6 +919,7 @@ main(int argc, char *argv[])
>
> signal(SIGINT, sig_die);
> signal(SIGTERM, sig_die);
> + signal(SIGCHLD, sig_child);
> signal_set(&sighup_ev, SIGHUP, gssd_scan_cb, NULL);
> signal_add(&sighup_ev, NULL);
> event_set(&inotify_ev, inotify_fd, EV_READ | EV_PERSIST, gssd_inotify_cb, NULL);
> diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
> index 11168b2..8f5ca03 100644
> --- a/utils/gssd/gssd_proc.c
> +++ b/utils/gssd/gssd_proc.c
> @@ -656,16 +656,9 @@ process_krb5_upcall(struct clnt_info *clp, uid_t uid, int fd, char *tgtname,
> /* fork() failed! */
> printerr(0, "WARNING: unable to fork() to handle"
> "upcall: %s\n", strerror(errno));
> - return;
> + /* FALLTHROUGH */
> default:
> - /* Parent: just wait on child to exit and return */
> - do {
> - pid = wait(&err);
> - } while(pid == -1 && errno != -ECHILD);
> -
> - if (WIFSIGNALED(err))
> - printerr(0, "WARNING: forked child was killed"
> - "with signal %d\n", WTERMSIG(err));
> + /* Parent: Return and wait for the SIGCHLD */
> return;
> }
> no_fork:
I was thinking that there was some reason that we couldn't do this --
that there were data structures that would get wiped if you got another
upcall while the first was being processed. The forking should prevent
that though, so I think this looks reasonable.
Acked-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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