* [RFC PATCH v5 0/2] hung_task: Display every hung task warning
@ 2014-01-23 10:56 Aaron Tomlin
2014-01-23 10:56 ` [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint Aaron Tomlin
2014-01-23 10:56 ` [RFC PATCH v5 2/2] hung_task: Display every hung task warning Aaron Tomlin
0 siblings, 2 replies; 5+ messages in thread
From: Aaron Tomlin @ 2014-01-23 10:56 UTC (permalink / raw)
To: mingo; +Cc: linux-kernel, rientjes, mingo, oleg, riel, akpm, atomlin
When khungtaskd detects hung tasks, it prints out backtraces from
a number of those tasks. Limiting the number of backtraces being
printed out can result in the user not seeing the information
necessary to debug the issue. The hung_task_warnings sysctl
controls this feature.
This patch makes it possible for hung_task_warnings to accept a
special value to print an unlimited number of backtraces when
khungtaskd detects hung tasks.
The special value is -1. To use this value it is necessary to
change types from ulong to int.
Rebased against v3.13-rc8.
Changes since v4:
- Improve the documentation on hung_task_warnings
Changes since v3:
- Simplify the commit message (Rik van Riel and David Rientjes)
- Document hung_task_* sysctl parameters (David Rientjes)
Aaron Tomlin (2):
sysctl: Make neg_one a standard constraint
hung_task: Display every hung task warning
Documentation/sysctl/kernel.txt | 42 +++++++++++++++++++++++++++++++++++++++++
include/linux/sched/sysctl.h | 2 +-
kernel/hung_task.c | 6 ++++--
kernel/sysctl.c | 6 ++++--
4 files changed, 51 insertions(+), 5 deletions(-)
--
1.8.4.2
^ permalink raw reply [flat|nested] 5+ messages in thread
* [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint
2014-01-23 10:56 [RFC PATCH v5 0/2] hung_task: Display every hung task warning Aaron Tomlin
@ 2014-01-23 10:56 ` Aaron Tomlin
2014-01-25 8:48 ` Ingo Molnar
2014-01-23 10:56 ` [RFC PATCH v5 2/2] hung_task: Display every hung task warning Aaron Tomlin
1 sibling, 1 reply; 5+ messages in thread
From: Aaron Tomlin @ 2014-01-23 10:56 UTC (permalink / raw)
To: mingo; +Cc: linux-kernel, rientjes, mingo, oleg, riel, akpm, atomlin
Add neg_one to the list of standard constraints.
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
---
kernel/sysctl.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 34a6047..dd531a6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -122,6 +122,7 @@ extern int blk_iopoll_enabled;
static int sixty = 60;
#endif
+static int neg_one = -1;
static int zero;
static int __maybe_unused one = 1;
static int __maybe_unused two = 2;
--
1.8.4.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [RFC PATCH v5 2/2] hung_task: Display every hung task warning
2014-01-23 10:56 [RFC PATCH v5 0/2] hung_task: Display every hung task warning Aaron Tomlin
2014-01-23 10:56 ` [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint Aaron Tomlin
@ 2014-01-23 10:56 ` Aaron Tomlin
1 sibling, 0 replies; 5+ messages in thread
From: Aaron Tomlin @ 2014-01-23 10:56 UTC (permalink / raw)
To: mingo; +Cc: linux-kernel, rientjes, mingo, oleg, riel, akpm, atomlin
When khungtaskd detects hung tasks, it prints out
backtraces from a number of those tasks.
Limiting the number of backtraces being printed
out can result in the user not seeing the information
necessary to debug the issue. The hung_task_warnings
sysctl controls this feature.
This patch makes it possible for hung_task_warnings
to accept a special value to print an unlimited
number of backtraces when khungtaskd detects hung
tasks.
The special value is -1. To use this value it is
necessary to change types from ulong to int.
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
---
Documentation/sysctl/kernel.txt | 43 +++++++++++++++++++++++++++++++++++++++++
include/linux/sched/sysctl.h | 2 +-
kernel/hung_task.c | 6 ++++--
kernel/sysctl.c | 5 +++--
4 files changed, 51 insertions(+), 5 deletions(-)
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 26b7ee4..aff1d31 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -33,6 +33,10 @@ show up in /proc/sys/kernel:
- domainname
- hostname
- hotplug
+- hung_task_panic
+- hung_task_check_count
+- hung_task_timeout_secs
+- hung_task_warnings
- kptr_restrict
- kstack_depth_to_print [ X86 only ]
- l2cr [ PPC only ]
@@ -287,6 +291,45 @@ Default value is "/sbin/hotplug".
==============================================================
+hung_task_panic:
+
+Controls the kernel's behavior when a hung task is detected.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+0: continue operation. This is the default behavior.
+
+1: panic immediately.
+
+==============================================================
+
+hung_task_check_count:
+
+The upper bound on the number of tasks that are checked.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+==============================================================
+
+hung_task_timeout_secs:
+
+Check interval. When a task in D state did not get scheduled
+for more than this value report a warning.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+0: means infinite timeout - no checking done.
+
+==============================================================
+
+hung_task_warning:
+
+The maximum number of warnings to report. During a check interval
+if a hung task is detected, this value is decreased by 1.
+When this value reaches 0, no more warnings will be reported.
+This file shows up if CONFIG_DETECT_HUNG_TASK is enabled.
+
+-1: report an infinite number of warnings.
+
+==============================================================
+
kptr_restrict:
This toggle indicates whether restrictions are placed on
diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 41467f8..eb3c72d7 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -5,7 +5,7 @@
extern int sysctl_hung_task_check_count;
extern unsigned int sysctl_hung_task_panic;
extern unsigned long sysctl_hung_task_timeout_secs;
-extern unsigned long sysctl_hung_task_warnings;
+extern int sysctl_hung_task_warnings;
extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
void __user *buffer,
size_t *lenp, loff_t *ppos);
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 9328b80..0b9c169 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -37,7 +37,7 @@ int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
*/
unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
-unsigned long __read_mostly sysctl_hung_task_warnings = 10;
+int __read_mostly sysctl_hung_task_warnings = 10;
static int __read_mostly did_panic;
@@ -98,7 +98,9 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
if (!sysctl_hung_task_warnings)
return;
- sysctl_hung_task_warnings--;
+
+ if (sysctl_hung_task_warnings > 0)
+ sysctl_hung_task_warnings--;
/*
* Ok, the task did not get scheduled for more than 2 minutes,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index dd531a6..b50cd13 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -985,9 +985,10 @@ static struct ctl_table kern_table[] = {
{
.procname = "hung_task_warnings",
.data = &sysctl_hung_task_warnings,
- .maxlen = sizeof(unsigned long),
+ .maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_doulongvec_minmax,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &neg_one,
},
#endif
#ifdef CONFIG_COMPAT
--
1.8.4.2
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint
2014-01-23 10:56 ` [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint Aaron Tomlin
@ 2014-01-25 8:48 ` Ingo Molnar
2014-01-25 8:58 ` Ingo Molnar
0 siblings, 1 reply; 5+ messages in thread
From: Ingo Molnar @ 2014-01-25 8:48 UTC (permalink / raw)
To: Aaron Tomlin; +Cc: linux-kernel, rientjes, mingo, oleg, riel, akpm
* Aaron Tomlin <atomlin@redhat.com> wrote:
> Add neg_one to the list of standard constraints.
>
> Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
> Acked-by: Rik van Riel <riel@redhat.com>
> Acked-by: David Rientjes <rientjes@google.com>
> ---
> kernel/sysctl.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 34a6047..dd531a6 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -122,6 +122,7 @@ extern int blk_iopoll_enabled;
> static int sixty = 60;
> #endif
>
> +static int neg_one = -1;
> static int zero;
> static int __maybe_unused one = 1;
> static int __maybe_unused two = 2;
So what happens if CONFIG_DETECT_HUNG_TASK is not defined and neg_one
is unused? The compiler generates an unused variable warning.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [RFC PATCH v5 1/2] sysctl: Make neg_one a standard constraint
2014-01-25 8:48 ` Ingo Molnar
@ 2014-01-25 8:58 ` Ingo Molnar
0 siblings, 0 replies; 5+ messages in thread
From: Ingo Molnar @ 2014-01-25 8:58 UTC (permalink / raw)
To: Aaron Tomlin; +Cc: linux-kernel, rientjes, mingo, oleg, riel, akpm
* Ingo Molnar <mingo@kernel.org> wrote:
>
> * Aaron Tomlin <atomlin@redhat.com> wrote:
>
> > Add neg_one to the list of standard constraints.
> >
> > Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
> > Acked-by: Rik van Riel <riel@redhat.com>
> > Acked-by: David Rientjes <rientjes@google.com>
> > ---
> > kernel/sysctl.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> > index 34a6047..dd531a6 100644
> > --- a/kernel/sysctl.c
> > +++ b/kernel/sysctl.c
> > @@ -122,6 +122,7 @@ extern int blk_iopoll_enabled;
> > static int sixty = 60;
> > #endif
> >
> > +static int neg_one = -1;
> > static int zero;
> > static int __maybe_unused one = 1;
> > static int __maybe_unused two = 2;
>
> So what happens if CONFIG_DETECT_HUNG_TASK is not defined and
> neg_one is unused? The compiler generates an unused variable
> warning.
Note, I fixed this up in your patch, no need to resend.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 5+ messages in thread
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2014-01-23 10:56 [RFC PATCH v5 0/2] hung_task: Display every hung task warning Aaron Tomlin
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2014-01-25 8:48 ` Ingo Molnar
2014-01-25 8:58 ` Ingo Molnar
2014-01-23 10:56 ` [RFC PATCH v5 2/2] hung_task: Display every hung task warning Aaron Tomlin
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