Messages in this thread Patch in this message | | | Date | Fri, 9 Sep 2016 13:13:44 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] hung_task: Allow hung_task_panic when hung_task_warnings is 0. |
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On Fri, 9 Sep 2016 15:43:34 -0400 jsiddle@redhat.com wrote:
> From: John Siddle <jsiddle@redhat.com> > > Previously hung_task_panic would not be respected if enabled after > hung_task_warnings had already been decremented to 0. > > Permit the kernel to panic if hung_task_panic is enabled after > hung_task_warnings has already been decremented to 0 and another task > hangs for hung_task_timeout_secs seconds. > > Check if hung_task_panic is enabled so we don't return prematurely, and > check if hung_task_warnings is non-zero so we don't print the warning > unnecessarily. > > ... > > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -98,7 +98,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > > trace_sched_process_hang(t); > > - if (!sysctl_hung_task_warnings) > + if (!sysctl_hung_task_warnings && !sysctl_hung_task_panic) > return; > > if (sysctl_hung_task_warnings > 0) > @@ -108,16 +108,18 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > * Ok, the task did not get scheduled for more than 2 minutes, > * complain: > */ > - pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", > - t->comm, t->pid, timeout); > - pr_err(" %s %s %.*s\n", > - print_tainted(), init_utsname()->release, > - (int)strcspn(init_utsname()->version, " "), > - init_utsname()->version); > - pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" > - " disables this message.\n"); > - sched_show_task(t); > - debug_show_held_locks(t); > + if (sysctl_hung_task_warnings) { > + pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", > + t->comm, t->pid, timeout); > + pr_err(" %s %s %.*s\n", > + print_tainted(), init_utsname()->release, > + (int)strcspn(init_utsname()->version, " "), > + init_utsname()->version); > + pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" > + " disables this message.\n"); > + sched_show_task(t); > + debug_show_held_locks(t); > + }
This introduces an off-by-one error. In the old code, if sysctl_hung_task_warnings==1 on entry, we warn. With the new code, we no longer warn.
This?
--- a/kernel/hung_task.c~hung_task-allow-hung_task_panic-when-hung_task_warnings-is-0-fix +++ a/kernel/hung_task.c @@ -101,14 +101,12 @@ static void check_hung_task(struct task_ if (!sysctl_hung_task_warnings && !sysctl_hung_task_panic) return; - if (sysctl_hung_task_warnings > 0) - sysctl_hung_task_warnings--; - /* * Ok, the task did not get scheduled for more than 2 minutes, * complain: */ if (sysctl_hung_task_warnings) { + sysctl_hung_task_warnings--; pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", t->comm, t->pid, timeout); pr_err(" %s %s %.*s\n", _
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