Return-Path: Received: from mail-qg0-f43.google.com ([209.85.192.43]:34533 "EHLO mail-qg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753164AbbIYKxV (ORCPT ); Fri, 25 Sep 2015 06:53:21 -0400 Received: by qgez77 with SMTP id z77so66078712qge.1 for ; Fri, 25 Sep 2015 03:53:20 -0700 (PDT) Date: Fri, 25 Sep 2015 06:53:17 -0400 From: Jeff Layton To: Steve Dickson Cc: Linux NFS Mailing list , Systemd Mailing List Subject: Re: [PATCH] gssd: Improve scalability by not waiting for child processes Message-ID: <20150925065317.6f5339cd@tlielax.poochiereds.net> In-Reply-To: <1443043250-25703-1-git-send-email-steved@redhat.com> References: <1443043250-25703-1-git-send-email-steved@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, 23 Sep 2015 17:20:50 -0400 Steve Dickson 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 > --- > 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 > #include > #include > #include > #include > #include > +#include > #include > #include > #include > @@ -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