Date: Fri, 27 Sep 2019 15:31:25 -0600 From: Warner Losh <imp@bsdimp.com> To: mike tancsa <mike@sentex.net> Cc: Aleksandr Rybalko <ray@ddteam.net>, freebsd-embedded <freebsd-embedded@freebsd.org> Subject: Re: watchdogd stat location Message-ID: <CANCZdfpq424LcV04dBJfoid_KSSdYWGfq2StDCToxDzZXnAvfg@mail.gmail.com> In-Reply-To: <fcdd9659-d7e4-c554-b501-6b8cd178f6d7@sentex.net> References: <5eba25eb-9ba4-0c93-27c8-e834491298ad@sentex.net> <CANCZdfp6bym5b6eFXFH0MxjYsAX%2B1Bi9fGXgp7sFM206zmsveQ@mail.gmail.com> <CAJ1Oi8FsG=nEBXdd0CS3U2zZSgh=SMcBO0ieY-KT5b1iDVFmJg@mail.gmail.com> <83831ae6-9275-4f0c-a23d-c9cca3dc28f4@sentex.net> <CANCZdfrRh7Ssf9vSSJ4Hopec1q7abLi9AdUqoPqZm4hPok6QUQ@mail.gmail.com> <fcdd9659-d7e4-c554-b501-6b8cd178f6d7@sentex.net>
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On Fri, Sep 27, 2019 at 2:30 PM mike tancsa <mike@sentex.net> wrote:
> On 9/27/2019 3:53 PM, Warner Losh wrote:
> > >
> >
> > I am all for that too. Just something other than /etc or /var
> > which are
> > often mounted on ramdisk.
> >
> >
> > I think that / is too special to cause disk IO to ever happen. Other
> > dirs will sometimes not be in the cache.... The notion here, perhaps
> > bogus, is that we want to check the root FS is sane. The stat(2) is a
> > cheap way to do this that will eventually fail if / goes wonky enough.
> > It's weak.
> >
> >
> Would something like this buy any extra sanity ? or not worth it. I
> guess fancier checks belong in a passed program
>
>
> # diff -u watchdogd.c.orig watchdogd.c
> --- watchdogd.c.orig 2019-09-27 16:27:14.456973000 -0400
> +++ watchdogd.c 2019-09-27 16:27:18.904885000 -0400
> @@ -364,9 +364,23 @@
>
> if (test_cmd != NULL)
> failed = system(test_cmd);
> - else
> - failed = stat("/etc", &sb);
> -
> + else {
> +
> + srand(time(NULL));
> + switch(rand() % 4) {
> + case 0:
> + failed = stat("/", &sb);
> + break;
> + case 1:
> + failed = stat("/bin", &sb);
> + break;
> + case 2:
> + failed = stat("/sbin", &sb);
> + break;
> + default:
> + failed = stat("/usr", &sb);
> + }
> + }
> error = watchdog_getuptime(&ts_end);
> if (error) {
> end_program = 1;
>
I don't think the rand helps at all. I think you'd really rather do things
sequentially. And this introduces more assumptions about the underlying
filesystem(s).
Warner
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