Messages in this thread | | | From | Dmitry Vyukov <> | Date | Wed, 20 Jun 2018 07:23:49 +0200 | Subject | Re: [PATCH v2] kernel/hung_task.c: allow to set checking interval separately from timeout |
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On Wed, Jun 20, 2018 at 1:03 AM, Andrew Morton <akpm@linux-foundation.org> wrote: > On Mon, 11 Jun 2018 13:10:04 +0200 Dmitry Vyukov <dvyukov@google.com> wrote: > >> Currently task hung checking interval is equal to timeout, >> as the result hung is detected anywhere between timeout and 2*timeout. >> This is fine for most interactive environments, but this hurts automated >> testing setups (syzbot). In an automated setup we need to strictly order >> CPU lockup < RCU stall < workqueue lockup < task hung < silent loss, >> so that RCU stall is not detected as task hung and task hung is not >> detected as silent machine loss. The large variance in task hung >> detection timeout requires setting silent machine loss timeout to >> a very large value (e.g. if task hung is 3 mins, then silent loss >> need to be set to ~7 mins). The additional 3 minutes significantly >> reduce testing efficiency because usually we crash kernel within >> a minute, and this can add hours to bug localization process as it >> needs to do dozens of tests. >> >> Allow setting checking interval separately from timeout. >> This allows to set timeout to, say, 3 minutes, >> but checking interval to 10 secs. >> >> The interval is controlled via a new hung_task_check_interval_secs >> sysctl, similar to the existing hung_task_timeout_secs sysctl. >> The default value of 0 results in the current behavior: >> checking interval is equal to timeout. > > I suppose we shoold do this:
Hi Andrew,
I see you added the patch and fixup to mm tree. Do you want me to resend v3 with the fixup included, or how does this work?
Thanks
> --- a/kernel/sysctl.c~kernel-hung_taskc-allow-to-set-checking-interval-separately-from-timeout-fix > +++ a/kernel/sysctl.c > @@ -145,7 +145,10 @@ static int minolduid; > static int ngroups_max = NGROUPS_MAX; > static const int cap_last_cap = CAP_LAST_CAP; > > -/*this is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs */ > +/* > + * This is needed for proc_doulongvec_minmax of sysctl_hung_task_timeout_secs > + * and hung_task_check_interval_secs > + */ > #ifdef CONFIG_DETECT_HUNG_TASK > static unsigned long hung_task_timeout_max = (LONG_MAX/HZ); > #endif
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