The patch titled Subject: kthread: introduce to_live_kthread() has been added to the -mm tree. Its filename is kthread-introduce-to_live_kthread.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Oleg Nesterov <oleg@xxxxxxxxxx> Subject: 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@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 | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff -puN kernel/kthread.c~kthread-introduce-to_live_kthread kernel/kthread.c --- a/kernel/kthread.c~kthread-introduce-to_live_kthread +++ a/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_cp 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); } /** _ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html