* [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks
@ 2014-04-09 3:50 Mike Galbraith
2014-04-13 13:40 ` Steven Rostedt
2014-05-08 10:41 ` [tip:sched/core] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check tip-bot for Steven Rostedt (Red Hat)
0 siblings, 2 replies; 4+ messages in thread
From: Mike Galbraith @ 2014-04-09 3:50 UTC (permalink / raw)
To: Steven Rostedt; +Cc: Peter Zijlstra, Ingo Molnar, LKML
Hi Steven,
Seems c92211d9b7727 introduced a buglet.
--snip--
Bail on task_pri >= MAX_RT_PRIO excludes userspace prio 98 and 99 tasks,
which map to 100 and 101 respectively.
A user reported that given two SCHED_RR tasks, one hog, one light, the light
task may be stacked on top of the hog iff prio >= 98, latency hit follows.
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: <stable@vger.kernel.org>
Fixes: c92211d9b7727 sched/cpupri: Remove the vec->lock
---
kernel/sched/cpupri.c | 3 ---
1 file changed, 3 deletions(-)
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,9 +70,6 @@ int cpupri_find(struct cpupri *cp, struc
int idx = 0;
int task_pri = convert_prio(p->prio);
- if (task_pri >= MAX_RT_PRIO)
- return 0;
-
for (idx = 0; idx < task_pri; idx++) {
struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
int skip = 0;
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks
2014-04-09 3:50 [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks Mike Galbraith
@ 2014-04-13 13:40 ` Steven Rostedt
2014-04-13 13:48 ` Steven Rostedt
2014-05-08 10:41 ` [tip:sched/core] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check tip-bot for Steven Rostedt (Red Hat)
1 sibling, 1 reply; 4+ messages in thread
From: Steven Rostedt @ 2014-04-13 13:40 UTC (permalink / raw)
To: Mike Galbraith; +Cc: Peter Zijlstra, Ingo Molnar, LKML
On Wed, 09 Apr 2014 05:50:10 +0200
Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
> Hi Steven,
>
> Seems c92211d9b7727 introduced a buglet.
>
> --snip--
>
> Bail on task_pri >= MAX_RT_PRIO excludes userspace prio 98 and 99 tasks,
> which map to 100 and 101 respectively.
>
> A user reported that given two SCHED_RR tasks, one hog, one light, the light
> task may be stacked on top of the hog iff prio >= 98, latency hit follows.
>
> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
> Cc: <stable@vger.kernel.org>
> Fixes: c92211d9b7727 sched/cpupri: Remove the vec->lock
> ---
> kernel/sched/cpupri.c | 3 ---
> 1 file changed, 3 deletions(-)
>
> --- a/kernel/sched/cpupri.c
> +++ b/kernel/sched/cpupri.c
> @@ -70,9 +70,6 @@ int cpupri_find(struct cpupri *cp, struc
> int idx = 0;
> int task_pri = convert_prio(p->prio);
>
> - if (task_pri >= MAX_RT_PRIO)
> - return 0;
task_pri is used as an index into pri_to_cpu. Although I don't see how
this can be called for a non RT task, the safer solution is below.
-- Steve
> -
> for (idx = 0; idx < task_pri; idx++) {
> struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
> int skip = 0;
>
>From 606aa467c9a51c09ce4efa320db45eee59a9bd06 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Sun, 13 Apr 2014 09:34:53 -0400
Subject: [PATCH] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in
cpupri check
The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Cc: stable@vger.kernel.org
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/sched/cpupri.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index 8b836b3..557356a 100644
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,7 +70,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
int idx = 0;
int task_pri = convert_prio(p->prio);
- if (task_pri >= MAX_RT_PRIO)
+ if (task_pri >= CPUPRI_NR_PRIORITIES)
return 0;
for (idx = 0; idx < task_pri; idx++) {
--
1.8.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks
2014-04-13 13:40 ` Steven Rostedt
@ 2014-04-13 13:48 ` Steven Rostedt
0 siblings, 0 replies; 4+ messages in thread
From: Steven Rostedt @ 2014-04-13 13:48 UTC (permalink / raw)
To: Mike Galbraith; +Cc: Peter Zijlstra, Ingo Molnar, LKML
Actually, since task_pri is calculated from convert_prio() that check
should never be hit. But, I'm paranoid, and instead of dropping the
check, we can do the same as what cpupri_set() does. Which is to BUG.
-- Steve
>From aac271901d6ef5ad19c52f166bf130ad27515b5f Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Sun, 13 Apr 2014 09:34:53 -0400
Subject: [PATCH] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in
cpupri check
The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.
As task_pri is computed from convert_prio() which should never be bigger
than CPUPRI_NR_PRIORITIES, if the check should cause a panic if it is
hit.
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Cc: stable@vger.kernel.org
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/sched/cpupri.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index 8b836b3..3031bac 100644
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,8 +70,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
int idx = 0;
int task_pri = convert_prio(p->prio);
- if (task_pri >= MAX_RT_PRIO)
- return 0;
+ BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);
for (idx = 0; idx < task_pri; idx++) {
struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
--
1.8.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [tip:sched/core] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check
2014-04-09 3:50 [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks Mike Galbraith
2014-04-13 13:40 ` Steven Rostedt
@ 2014-05-08 10:41 ` tip-bot for Steven Rostedt (Red Hat)
1 sibling, 0 replies; 4+ messages in thread
From: tip-bot for Steven Rostedt (Red Hat) @ 2014-05-08 10:41 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, rostedt, peterz, tglx, umgwanakikbuti
Commit-ID: 6227cb00cc120f9a43ce8313bb0475ddabcb7d01
Gitweb: http://git.kernel.org/tip/6227cb00cc120f9a43ce8313bb0475ddabcb7d01
Author: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
AuthorDate: Sun, 13 Apr 2014 09:34:53 -0400
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 7 May 2014 11:51:33 +0200
sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check
The check at the beginning of cpupri_find() makes sure that the task_pri
variable does not exceed the cp->pri_to_cpu array length. But that length
is CPUPRI_NR_PRIORITIES not MAX_RT_PRIO, where it will miss the last two
priorities in that array.
As task_pri is computed from convert_prio() which should never be bigger
than CPUPRI_NR_PRIORITIES, if the check should cause a panic if it is
hit.
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1397015410.5212.13.camel@marge.simpson.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/cpupri.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
index 8b836b3..3031bac 100644
--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -70,8 +70,7 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
int idx = 0;
int task_pri = convert_prio(p->prio);
- if (task_pri >= MAX_RT_PRIO)
- return 0;
+ BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);
for (idx = 0; idx < task_pri; idx++) {
struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-05-08 10:42 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2014-04-09 3:50 [PATCH] sched/cpupri: fix cpupri_find() for high priority tasks Mike Galbraith
2014-04-13 13:40 ` Steven Rostedt
2014-04-13 13:48 ` Steven Rostedt
2014-05-08 10:41 ` [tip:sched/core] sched: Use CPUPRI_NR_PRIORITIES instead of MAX_RT_PRIO in cpupri check tip-bot for Steven Rostedt (Red Hat)
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