The patch titled make kthread_create() more scalable has been added to the -mm tree. Its filename is make-kthread_create-more-scalable.patch *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this ------------------------------------------------------ Subject: make kthread_create() more scalable From: Oleg Nesterov <oleg@xxxxxxxxxx> If kernel_thread(kthread) succeeds, kthread() can not fail on its path to complete(&create->started) + schedule(). After that it can't be woken because nobody can see the new task yet. This means: - we don't need tasklist_lock for find_task_by_pid(). - create_kthread() doesn't need to wait for create->started. Instead, kthread_create() first waits for create->created to get the result of kernel_thread(), then waits for create->started to synchronize with kthread(). Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/kthread.c | 42 ++++++++++++++++++++---------------------- 1 files changed, 20 insertions(+), 22 deletions(-) diff -puN kernel/kthread.c~make-kthread_create-more-scalable kernel/kthread.c --- a/kernel/kthread.c~make-kthread_create-more-scalable +++ a/kernel/kthread.c @@ -24,11 +24,11 @@ struct kthread_create_info /* Information passed to kthread() from kthreadd. */ int (*threadfn)(void *data); void *data; + struct completion created; struct completion started; /* Result passed back to kthread_create() from kthreadd. */ - struct task_struct *result; - struct completion done; + pid_t result; struct list_head list; }; @@ -91,15 +91,9 @@ static void create_kthread(struct kthrea /* We want our own signal handler (we take no signals by default). */ pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD); - if (pid < 0) { - create->result = ERR_PTR(pid); - } else { - wait_for_completion(&create->started); - read_lock(&tasklist_lock); - create->result = find_task_by_pid(pid); - read_unlock(&tasklist_lock); - } - complete(&create->done); + create->result = pid; + + complete(&create->created); } /** @@ -127,27 +121,31 @@ struct task_struct *kthread_create(int ( ...) { struct kthread_create_info create; + struct task_struct *ret; + va_list args; create.threadfn = threadfn; create.data = data; + init_completion(&create.created); init_completion(&create.started); - init_completion(&create.done); spin_lock(&kthread_create_lock); list_add_tail(&create.list, &kthread_create_list); - wake_up_process(kthreadd_task); spin_unlock(&kthread_create_lock); + wake_up_process(kthreadd_task); - wait_for_completion(&create.done); + wait_for_completion(&create.created); + if (create.result < 0) + return ERR_PTR(create.result); + + wait_for_completion(&create.started); + ret = find_task_by_pid(create.result); + + va_start(args, namefmt); + vsnprintf(ret->comm, sizeof(ret->comm), namefmt, args); + va_end(args); - if (!IS_ERR(create.result)) { - va_list args; - va_start(args, namefmt); - vsnprintf(create.result->comm, sizeof(create.result->comm), - namefmt, args); - va_end(args); - } - return create.result; + return ret; } EXPORT_SYMBOL(kthread_create); _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are kernel-doc-fix-plisth-comments.patch git-dvb.patch smaps-add-clear_refs-file-to-clear-reference-fix.patch fix-refrigerator-vs-thaw_process-race.patch doc-atomic_add_unless-doesnt-imply-mb-on-failure.patch clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch allow-access-to-proc-pid-fd-after-setuid.patch freezer-task-exit_state-should-be-treated-as-bolean.patch softlockup-trivial-s-99-max_rt_prio.patch fix-race-between-proc_get_inode-and-remove_proc_entry.patch getrusage-fill-ru_inblock-and-ru_oublock-fields-if-possible.patch futex-restartable-futex_wait.patch futex-restartable-futex_wait-fix.patch add-support-for-deferrable-timers-respun.patch add-support-for-deferrable-timers-respun-tidy.patch add-support-for-deferrable-timers-respun-fix.patch add-a-new-deferrable-delayed-work-init.patch reimplement-flush_workqueue.patch implement-flush_work.patch implement-flush_work-sanity.patch implement-flush_work_keventd.patch flush_workqueue-use-preempt_disable-to-hold-off-cpu-hotplug.patch flush_cpu_workqueue-dont-flush-an-empty-worklist.patch aio-use-flush_work.patch kblockd-use-flush_work.patch relayfs-use-flush_keventd_work.patch tg3-use-flush_keventd_work.patch e1000-use-flush_keventd_work.patch libata-use-flush_work.patch phy-use-flush_work.patch call-cpu_chain-with-cpu_down_failed-if-cpu_down_prepare-failed.patch slab-use-cpu_lock_.patch workqueue-fix-freezeable-workqueues-implementation.patch workqueue-fix-flush_workqueue-vs-cpu_dead-race.patch workqueue-dont-clear-cwq-thread-until-it-exits.patch workqueue-dont-migrate-pending-works-from-the-dead-cpu.patch workqueue-kill-run_scheduled_work.patch workqueue-dont-save-interrupts-in-run_workqueue.patch workqueue-make-cancel_rearming_delayed_workqueue-work-on-idle-dwork.patch workqueue-introduce-cpu_singlethread_map.patch workqueue-introduce-workqueue_struct-singlethread.patch workqueue-make-init_workqueues-__init.patch make-queue_delayed_work-friendly-to-flush_fork.patch unify-queue_delayed_work-and-queue_delayed_work_on.patch workqueue-introduce-wq_per_cpu-helper.patch make-cancel_rearming_delayed_work-work-on-any-workqueue-not-just-keventd_wq.patch ipvs-flush-defense_work-before-module-unload.patch workqueue-kill-noautorel-works.patch worker_thread-dont-play-with-signals.patch worker_thread-fix-racy-try_to_freeze-usage.patch zap_other_threads-remove-unneeded-exit_signal-change.patch slab-shutdown-cache_reaper-when-cpu-goes-down.patch unify-flush_work-flush_work_keventd-and-rename-it-to-cancel_work_sync.patch ____call_usermodehelper-dont-flush_signals.patch freezer-read-pf_borrowed_mm-in-a-nonracy-way.patch freezer-close-theoretical-race-between-refrigerator-and-thaw_tasks.patch freezer-remove-pf_nofreeze-from-rcutorture-thread.patch freezer-remove-pf_nofreeze-from-bluetooth-threads.patch freezer-add-try_to_freeze-calls-to-all-kernel-threads.patch freezer-fix-vfork-problem.patch freezer-take-kernel_execve-into-consideration.patch kthread-dont-depend-on-work-queues-take-2.patch kthread-dont-depend-on-work-queues-take-2-fix.patch change-reparent_to_init-to-reparent_to_kthreadd.patch nlmclnt_recovery-dont-use-clone_sighand.patch usbatm_heavy_init-dont-use-clone_sighand.patch pnpbios_thread_init-dont-use-clone_sighand.patch wait_for_helper-remove-unneeded-do_sigaction.patch worker_thread-dont-play-with-sigchld-and-numa-policy.patch change-kernel-threads-to-ignore-signals-instead-of-blocking-them.patch fix-kthread_create-vs-freezer-theoretical-race.patch make-kthread_create-more-scalable.patch dont-init-pgrp-and-__session-in-init_signals.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