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author | Oleg Nesterov <oleg@redhat.com> | 2013-04-29 15:05:01 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-04-29 15:54:25 -0700 |
commit | 4ecdafc8084fe1d95bb59ed7753b345abcd586fb (patch) | |
tree | b119ed319cfb2f526ac5666f04bef7e13caecd3c /kernel | |
parent | ec25e246b94a3233ab064994ef05a170bdba0e7c (diff) | |
download | linux-4ecdafc8084fe1d95bb59ed7753b345abcd586fb.tar.gz linux-4ecdafc8084fe1d95bb59ed7753b345abcd586fb.tar.bz2 linux-4ecdafc8084fe1d95bb59ed7753b345abcd586fb.zip |
kthread: introduce to_live_kthread()
"k->vfork_done != NULL" with a barrier() after to_kthread(k) in
task_get_live_kthread(k) looks unclear, and sub-optimal because we load
->vfork_done twice.
All we need is to ensure that we do not return to_kthread(NULL). Add a
new trivial helper which loads/checks ->vfork_done once, this also looks
more understandable.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/kthread.c | 26 |
1 files changed, 16 insertions, 10 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c index 9eb7fed0bbaa..a84dee265f94 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -52,8 +52,21 @@ enum KTHREAD_BITS { KTHREAD_IS_PARKED, }; -#define to_kthread(tsk) \ - container_of((tsk)->vfork_done, struct kthread, exited) +#define __to_kthread(vfork) \ + container_of(vfork, struct kthread, exited) + +static inline struct kthread *to_kthread(struct task_struct *k) +{ + return __to_kthread(k->vfork_done); +} + +static struct kthread *to_live_kthread(struct task_struct *k) +{ + struct completion *vfork = ACCESS_ONCE(k->vfork_done); + if (likely(vfork)) + return __to_kthread(vfork); + return NULL; +} /** * kthread_should_stop - should this kthread return now? @@ -313,15 +326,8 @@ struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), static struct kthread *task_get_live_kthread(struct task_struct *k) { - struct kthread *kthread; - get_task_struct(k); - kthread = to_kthread(k); - /* It might have exited */ - barrier(); - if (k->vfork_done != NULL) - return kthread; - return NULL; + return to_live_kthread(k); } static void __kthread_unpark(struct task_struct *k, struct kthread *kthread) |