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Date: Sat, 5 Jul 2014 03:46:25 -0700
From: tip-bot for Kirill Tkhai <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: ktkhai@...allels.com, mingo@...nel.org,
torvalds@...ux-foundation.org, peterz@...radead.org,
fabf@...net.be, todd.e.brandt@...ux.intel.com,
akpm@...ux-foundation.org, wangyun@...ux.vnet.ibm.com,
tglx@...utronix.de, linux-kernel@...r.kernel.org, hpa@...or.com,
bsegall@...gle.com, pjt@...gle.com,
srivatsa.bhat@...ux.vnet.ibm.com, rafael.j.wysocki@...el.com,
toshi.kani@...com, khorenko@...allels.com,
umgwanakikbuti@...il.com, ego@...ux.vnet.ibm.com,
srikar@...ux.vnet.ibm.com, paul.gortmaker@...driver.com
Subject: [tip:sched/core] sched: Rework check_for_tasks()
Commit-ID: b728ca06029d085a1585c1926610f26de93b9146
Gitweb: http://git.kernel.org/tip/b728ca06029d085a1585c1926610f26de93b9146
Author: Kirill Tkhai <ktkhai@...allels.com>
AuthorDate: Wed, 25 Jun 2014 12:19:55 +0400
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 5 Jul 2014 11:17:45 +0200
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@...allels.com>
Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Fabian Frederick <fabf@...net.be>
Cc: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
Cc: Konstantin Khorenko <khorenko@...allels.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Michael wang <wangyun@...ux.vnet.ibm.com>
Cc: Mike Galbraith <umgwanakikbuti@...il.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Paul Turner <pjt@...gle.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: Todd E Brandt <todd.e.brandt@...ux.intel.com>
Cc: Toshi Kani <toshi.kani@...com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1403684395.3462.44.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
kernel/cpu.c | 33 ++++++++++++++++++++-------------
1 file changed, 20 insertions(+), 13 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index a343bde..81e2a38 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -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;
- 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);
+ 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;
+
+ pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
+ 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 {
--
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