Commit 85653af7 authored Jul 15, 2007 by Satoru Takeuchi Committed by Linus Torvalds Jul 16, 2007

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>

parent 647bd61a

kernel/stop_machine.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -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, &param);

		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, &param);
		kthread_bind(p, cpu);
		wake_up_process(p);
		wait_for_completion(&smdata.done);

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