The patch titled
kthreads: simplify migration_thread() exit path
has been added to the -mm tree. Its filename is
kthreads-simplify-migration_thread-exit-path.patch
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------------------------------------------------------
Subject: kthreads: simplify migration_thread() exit path
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Now that kthread_stop() can be used even if the task has already exited,
we can kill the "wait_to_die:" loop in migration_thread(). But we must
pin rq->migration_thread after creation.
Actually, I don't think CPU_UP_CANCELED or CPU_DEAD should wait for
->migration_thread exit. Perhaps we can simplify this code a bit more.
migration_call() can set ->should_stop and forget about this thread. But
we need a new helper in kthred.c for that.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Vitaliy Gusev <vgusev@xxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
diff -puN kernel/sched.c~kthreads-simplify-migration_thread-exit-path kernel/sched.c
--- a/kernel/sched.c~kthreads-simplify-migration_thread-exit-path
+++ a/kernel/sched.c
@@ -6359,7 +6359,7 @@ static int migration_thread(void *data)
if (cpu_is_offline(cpu)) {
spin_unlock_irq(&rq->lock);
- goto wait_to_die;
+ break;
}
if (rq->active_balance) {
@@ -6385,16 +6385,7 @@ static int migration_thread(void *data)
complete(&req->done);
}
__set_current_state(TASK_RUNNING);
- return 0;
-wait_to_die:
- /* Wait for kthread_stop */
- set_current_state(TASK_INTERRUPTIBLE);
- while (!kthread_should_stop()) {
- schedule();
- set_current_state(TASK_INTERRUPTIBLE);
- }
- __set_current_state(TASK_RUNNING);
return 0;
}
@@ -6800,6 +6791,7 @@ migration_call(struct notifier_block *nf
rq = task_rq_lock(p, &flags);
__setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
task_rq_unlock(rq, &flags);
+ get_task_struct(p);
cpu_rq(cpu)->migration_thread = p;
break;
@@ -6828,6 +6820,7 @@ migration_call(struct notifier_block *nf
kthread_bind(cpu_rq(cpu)->migration_thread,
cpumask_any(cpu_online_mask));
kthread_stop(cpu_rq(cpu)->migration_thread);
+ put_task_struct(cpu_rq(cpu)->migration_thread);
cpu_rq(cpu)->migration_thread = NULL;
break;
@@ -6837,6 +6830,7 @@ migration_call(struct notifier_block *nf
migrate_live_tasks(cpu);
rq = cpu_rq(cpu);
kthread_stop(rq->migration_thread);
+ put_task_struct(rq->migration_thread);
rq->migration_thread = NULL;
/* Idle task back to normal (off runqueue, low prio) */
spin_lock_irq(&rq->lock);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
wait-prevent-exclusive-waiter-starvation.patch
linux-next.patch
pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch
get_mm_hiwater_xxx-trivial-s-define-inline.patch
getrusage-fill-ru_maxrss-value.patch
ptrace-kill-__ptrace_detach-fix-exit_state-check.patch
ptrace-simplify-ptrace_exit-ignoring_children-path.patch
ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch
ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit-fix.patch
ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch
reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch
reparent_thread-fix-the-is-it-traced-check.patch
reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch
forget_original_parent-cleanup-ptrace-pathes.patch
kthread-dont-looking-for-a-task-in-create_kthread-2.patch
kthreads-move-sched-realeted-initialization-from-kthreadd-context.patch
kthreads-simplify-the-startup-synchronization.patch
kthreads-rework-kthread_stop.patch
kthreads-simplify-migration_thread-exit-path.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch
pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch
pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch
pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch
pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch
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