From 85653af7d488702165eba72c6c1dd0250fae4e70 Mon Sep 17 00:00:00 2001
From: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Date: Sun, 15 Jul 2007 23:39:47 -0700
Subject: [PATCH] Fix stop_machine_run problem with naughty real time process
stop_machine_run() does its work on "kstopmachine" thread having max
priority. However that thread get such priority after woken up.
Therefore, in the following case ...
- "kstopmachine" try to run on CPU1
- There is a real time process which doesn't relinquish CPU time
voluntary on CPU1
... "kstopmachine" can't start to run and the CPU on which
stop_machine_run() is runing hangs up. To fix this problem, call
sched_setscheduler() before waking up that thread.
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
kernel/stop_machine.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index fcee2a8e6da37..319821ef78afc 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -93,10 +93,6 @@ static void stopmachine_set_state(enum stopmachine_state state)
static int stop_machine(void)
{
int i, ret = 0;
- struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-
- /* One high-prio thread per cpu. We'll do this one. */
- sched_setscheduler(current, SCHED_FIFO, ¶m);
atomic_set(&stopmachine_thread_ack, 0);
stopmachine_num_threads = 0;
@@ -189,6 +185,10 @@ struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
p = kthread_create(do_stop, &smdata, "kstopmachine");
if (!IS_ERR(p)) {
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+
+ /* One high-prio thread per cpu. We'll do this one. */
+ sched_setscheduler(p, SCHED_FIFO, ¶m);
kthread_bind(p, cpu);
wake_up_process(p);
wait_for_completion(&smdata.done);
--
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