The patch titled
cpu hotplug: fix ksoftirqd termination on cpu hotplug with naughty realtime process
has been added to the -mm tree. Its filename is
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: cpu hotplug: fix ksoftirqd termination on cpu hotplug with naughty realtime process
From: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Fix ksoftirqd termination on cpu hotplug with naughty real time process.
Assuming the following case:
- Try to hot remove CPU2 from CPU1.
- There is a real time process on CPU2, and that process doesn't sleep at all.
- That rt process and ksoftirqd/2 is migrated to the CPU0
Then ksoftirqd/2 can't stop becasue that rt process runs everlastingly on
CPU0, and CPU1 waiting the ksoftirqd/2's termination hangs up. To fix this
problem, set the priority of ksoftirqd/2 to max one before kthread_stop().
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/softirq.c | 2 ++
1 files changed, 2 insertions(+)
diff -puN kernel/softirq.c~cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process kernel/softirq.c
--- a/kernel/softirq.c~cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process
+++ a/kernel/softirq.c
@@ -590,6 +590,7 @@ static int __cpuinit cpu_callback(struct
{
int hotcpu = (unsigned long)hcpu;
struct task_struct *p;
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
switch (action) {
case CPU_UP_PREPARE:
@@ -618,6 +619,7 @@ static int __cpuinit cpu_callback(struct
case CPU_DEAD_FROZEN:
p = per_cpu(ksoftirqd, hotcpu);
per_cpu(ksoftirqd, hotcpu) = NULL;
+ sched_setscheduler(p, SCHED_FIFO, ¶m);
kthread_stop(p);
takeover_tasklets(hotcpu);
break;
_
Patches currently in -mm which might be from takeuchi_satoru@xxxxxxxxxxxxxx are
fix-stop_machine_run-problem-with-naughty-real-time-process.patch
cpu-hotplug-fix-ksoftirqd-termination-on-cpu-hotplug-with-naughty-realtime-process.patch
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