The patch titled
Subject: kthread: kill task_get_live_kthread()
has been added to the -mm tree. Its filename is
kthread-kill-task_get_live_kthread.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: kthread: kill task_get_live_kthread()
task_get_live_kthread() looks confusing and unneeded. It does
get_task_struct() but only kthread_stop() needs this, it can be called
even if the calller doesn't have a reference when we know that this
kthread can't exit until we do kthread_stop().
kthread_park() and kthread_unpark() do not need get_task_struct(), the
callers already have the reference. And it can not help if we can race
with the exiting kthread anyway, kthread_park() can hang forever in this
case.
Change kthread_park() and kthread_unpark() to use to_live_kthread(),
change kthread_stop() to do get_task_struct() by hand and remove
task_get_live_kthread().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kthread.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff -puN kernel/kthread.c~kthread-kill-task_get_live_kthread kernel/kthread.c
--- a/kernel/kthread.c~kthread-kill-task_get_live_kthread
+++ a/kernel/kthread.c
@@ -324,12 +324,6 @@ struct task_struct *kthread_create_on_cp
return p;
}
-static struct kthread *task_get_live_kthread(struct task_struct *k)
-{
- get_task_struct(k);
- return to_live_kthread(k);
-}
-
/**
* kthread_unpark - unpark a thread created by kthread_create().
* @k: thread created by kthread_create().
@@ -340,7 +334,7 @@ static struct kthread *task_get_live_kth
*/
void kthread_unpark(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread = to_live_kthread(k);
if (kthread) {
clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
@@ -356,7 +350,6 @@ void kthread_unpark(struct task_struct *
wake_up_process(k);
}
}
- put_task_struct(k);
}
/**
@@ -373,7 +366,7 @@ void kthread_unpark(struct task_struct *
*/
int kthread_park(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread = to_live_kthread(k);
int ret = -ENOSYS;
if (kthread) {
@@ -386,7 +379,6 @@ int kthread_park(struct task_struct *k)
}
ret = 0;
}
- put_task_struct(k);
return ret;
}
@@ -407,10 +399,13 @@ int kthread_park(struct task_struct *k)
*/
int kthread_stop(struct task_struct *k)
{
- struct kthread *kthread = task_get_live_kthread(k);
+ struct kthread *kthread;
int ret;
trace_sched_kthread_stop(k);
+
+ get_task_struct(k);
+ kthread = to_live_kthread(k);
if (kthread) {
set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
@@ -418,10 +413,9 @@ int kthread_stop(struct task_struct *k)
wait_for_completion(&kthread->exited);
}
ret = k->exit_code;
-
put_task_struct(k);
- trace_sched_kthread_stop_ret(ret);
+ trace_sched_kthread_stop_ret(ret);
return ret;
}
EXPORT_SYMBOL(kthread_stop);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
thinkpad-acpi-kill-hotkey_thread_mutex.patch
kthread-introduce-to_live_kthread.patch
kthread-kill-task_get_live_kthread.patch
lockdep-introduce-lock_acquire_exclusive-shared-helper-macros.patch
lglock-update-lockdep-annotations-to-report-recursive-local-locks.patch
ptrace-add-ability-to-retrieve-signals-without-removing-from-a-queue-v4.patch
selftest-add-a-test-case-for-ptrace_peeksiginfo.patch
signal-always-clear-sa_restorer-on-execve.patch
coredump-only-sigkill-should-interrupt-the-coredumping-task.patch
coredump-ensure-that-sigkill-always-kills-the-dumping-thread.patch
coredump-sanitize-the-setting-of-signal-group_exit_code.patch
coredump-introduce-dump_interrupted.patch
coredump-factor-out-the-setting-of-pf_dumpcore.patch
coredump-change-wait_for_dump_helpers-to-use-wait_event_interruptible.patch
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