Messages in this thread Patch in this message | | | Date | Tue, 19 Jun 2018 16:03:27 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v2] kernel/hung_task.c: allow to set checking interval separately from timeout |
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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:
--- 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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