On Thu, Sep 24 2009, Martin Orr wrote:
> With kernel 2.6.31, restorecond uses 99% of my CPU.
>
> This is because removing and readding the watch on utmp triggers inotify to
> return an IN_IGNORED event for the old watch descriptor. If the watch gets
> allocated the same wd when it is readded, then restorecond thinks that utmp
> has changed, so removes and readds the watch again, potentially looping.
>
> With kernel <= 2.6.30, this never happened, because the kernel didn't reuse
> watch descriptors. So the IN_IGNORED event comes with a wd that is no
> longer in use, and gets ignored. But kernel 2.6.31 reuses the same watch
> descriptor.
>
> This patch fixes that by ignoring inotify events whose only bit set is
> IN_IGNORED.
>
> Note: it is not clear to me why it is necessary to remove and readd the
> watch in the first place.
>
> Note for testing: you need to log in (to cause a change in utmp) after
> starting restorecond to trigger the bug. In fact you need to log in twice
> before the kernel reuses a watch descriptor.
I can confirm seeing this behaviour, and that the patch fixed
the problem for me.
manoj
Tested-by: Manoj Srivastava <srivasta@xxxxxxxxxx>
> ---
> policycoreutils/restorecond/restorecond.c | 29 ++++++++++++++++-------------
> 1 files changed, 16 insertions(+), 13 deletions(-)
>
> diff --git a/policycoreutils/restorecond/restorecond.c
> b/policycoreutils/restorecond/restorecond.c
> index 58774e6..4952632 100644
> --- a/policycoreutils/restorecond/restorecond.c
> +++ b/policycoreutils/restorecond/restorecond.c
> @@ -315,21 +315,24 @@ static int watch(int fd)
> printf("wd=%d mask=%u cookie=%u len=%u\n",
> event->wd, event->mask,
> event->cookie, event->len);
> - if (event->wd == master_wd)
> - read_config(fd);
> - else {
> - switch (utmpwatcher_handle(fd, event->wd)) {
> - case -1: /* Message was not for utmpwatcher */
> - if (event->len)
> - watch_list_find(event->wd, event->name);
> - break;
>
> - case 1: /* utmp has changed need to reload */
> + if (event->mask & ~IN_IGNORED) {
> + if (event->wd == master_wd)
> read_config(fd);
> - break;
> -
> - default: /* No users logged in or out */
> - break;
> + else {
> + switch (utmpwatcher_handle(fd, event->wd)) {
> + case -1: /* Message was not for utmpwatcher */
> + if (event->len)
> + watch_list_find(event->wd, event->name);
> + break;
> +
> + case 1: /* utmp has changed need to reload */
> + read_config(fd);
> + break;
> +
> + default: /* No users logged in or out */
> + break;
> + }
> }
> }
--
Manoj Srivastava <srivasta@xxxxxxx> <http://www.golden-gryphon.com/>
1024D/BF24424C print 4966 F272 D093 B493 410B 924B 21BA DABB BF24 424C
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