Commit b728ca06 authored Jun 25, 2014 by Kirill Tkhai Committed by Ingo Molnar Jul 05, 2014

sched: Rework check_for_tasks()



1) Iterate thru all of threads in the system.
   Check for all threads, not only for group leaders.

2) Check for p->on_rq instead of p->state and cputime.
   Preempted task in !TASK_RUNNING state  OR just
   created task may be queued, that we want to be
   reported too.

3) Use read_lock() instead of write_lock().
   This function does not change any structures, and
   read_lock() is enough.

Signed-off-by: Kirill Tkhai <ktkhai@parallels.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Cc: Konstantin Khorenko <khorenko@parallels.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael wang <wangyun@linux.vnet.ibm.com>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paul Turner <pjt@google.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Todd E Brandt <todd.e.brandt@linux.intel.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403684395.3462.44.camel@tkhai


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 99b62567

kernel/cpu.c

+20 −13

Original line number	Diff line number	Diff line
		@@ -274,21 +274,28 @@ void clear_tasks_mm_cpumask(int cpu)
		rcu_read_unlock();
		}

		static inline void check_for_tasks(int cpu)
		static inline void check_for_tasks(int dead_cpu)
		{
		struct task_struct *p;
		cputime_t utime, stime;
		struct task_struct g, p;

		read_lock_irq(&tasklist_lock);
		do_each_thread(g, p) {
		if (!p->on_rq)
		continue;
		/*
		* We do the check with unlocked task_rq(p)->lock.
		* Order the reading to do not warn about a task,
		* which was running on this cpu in the past, and
		* it's just been woken on another cpu.
		*/
		rmb();
		if (task_cpu(p) != dead_cpu)
		continue;

		write_lock_irq(&tasklist_lock);
		for_each_process(p) {
		task_cputime(p, &utime, &stime);
		if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
		(utime \|\| stime))
		pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
		p->comm, task_pid_nr(p), cpu,
		p->state, p->flags);
		}
		write_unlock_irq(&tasklist_lock);
		p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
		} while_each_thread(g, p);
		read_unlock_irq(&tasklist_lock);
		}

		struct take_cpu_down_param {