X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=kernel%2Fkthread.c;h=c22700a3637a8233588fa7f850160dd52afbece8;hb=97bf2856c6014879bd04983a3e9dfcdac1e7fe85;hp=5689ebb1a250c8e57168208421ac3e4cd5af4543;hpb=9bf4aaab3e101692164d49b7ca357651eb691cb6;p=linux-2.6.git diff --git a/kernel/kthread.c b/kernel/kthread.c index 5689ebb1a..c22700a36 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -12,8 +12,15 @@ #include #include #include +#include #include +/* + * We dont want to execute off keventd since it might + * hold a semaphore our callers hold too: + */ +static struct workqueue_struct *helper_wq; + struct kthread_create_info { /* Information passed to kthread() from keventd. */ @@ -24,6 +31,8 @@ struct kthread_create_info /* Result passed back to kthread_create() from keventd. */ struct task_struct *result; struct completion done; + + struct work_struct work; }; struct kthread_stop_info @@ -35,9 +44,16 @@ struct kthread_stop_info /* Thread stopping is done by setthing this var: lock serializes * multiple kthread_stop calls. */ -static DECLARE_MUTEX(kthread_stop_lock); +static DEFINE_MUTEX(kthread_stop_lock); static struct kthread_stop_info kthread_stop_info; +/** + * kthread_should_stop - should this kthread return now? + * + * When someone calls kthread_stop on your kthread, it will be woken + * and this will return true. You should then return, and your return + * value will be passed through to kthread_stop(). + */ int kthread_should_stop(void) { return (kthread_stop_info.k == current); @@ -97,9 +113,10 @@ static int kthread(void *_create) } /* We are keventd: create a thread. */ -static void keventd_create_kthread(void *_create) +static void keventd_create_kthread(struct work_struct *work) { - struct kthread_create_info *create = _create; + struct kthread_create_info *create = + container_of(work, struct kthread_create_info, work); int pid; /* We want our own signal handler (we take no signals by default). */ @@ -108,30 +125,52 @@ static void keventd_create_kthread(void *_create) create->result = ERR_PTR(pid); } else { wait_for_completion(&create->started); - create->result = find_task_by_pid(pid); + read_lock(&tasklist_lock); + create->result = find_task_by_real_pid(pid); + read_unlock(&tasklist_lock); } complete(&create->done); } +/** + * kthread_create - create a kthread. + * @threadfn: the function to run until signal_pending(current). + * @data: data ptr for @threadfn. + * @namefmt: printf-style name for the thread. + * + * Description: This helper function creates and names a kernel + * thread. The thread will be stopped: use wake_up_process() to start + * it. See also kthread_run(), kthread_create_on_cpu(). + * + * When woken, the thread will run @threadfn() with @data as its + * argument. @threadfn can either call do_exit() directly if it is a + * standalone thread for which noone will call kthread_stop(), or + * return when 'kthread_should_stop()' is true (which means + * kthread_stop() has been called). The return value should be zero + * or a negative error number; it will be passed to kthread_stop(). + * + * Returns a task_struct or ERR_PTR(-ENOMEM). + */ struct task_struct *kthread_create(int (*threadfn)(void *data), void *data, const char namefmt[], ...) { struct kthread_create_info create; - DECLARE_WORK(work, keventd_create_kthread, &create); create.threadfn = threadfn; create.data = data; init_completion(&create.started); init_completion(&create.done); + INIT_WORK(&create.work, keventd_create_kthread); - /* If we're being called to start the first workqueue, we - * can't use keventd. */ - if (!keventd_up()) - work.func(work.data); + /* + * The workqueue needs to start up first: + */ + if (!helper_wq) + create.work.func(&create.work); else { - schedule_work(&work); + queue_work(helper_wq, &create.work); wait_for_completion(&create.done); } if (!IS_ERR(create.result)) { @@ -146,6 +185,15 @@ struct task_struct *kthread_create(int (*threadfn)(void *data), } EXPORT_SYMBOL(kthread_create); +/** + * kthread_bind - bind a just-created kthread to a cpu. + * @k: thread created by kthread_create(). + * @cpu: cpu (might not be online, must be possible) for @k to run on. + * + * Description: This function is equivalent to set_cpus_allowed(), + * except that @cpu doesn't need to be online, and the thread must be + * stopped (i.e., just returned from kthread_create(). + */ void kthread_bind(struct task_struct *k, unsigned int cpu) { BUG_ON(k->state != TASK_INTERRUPTIBLE); @@ -156,18 +204,31 @@ void kthread_bind(struct task_struct *k, unsigned int cpu) } EXPORT_SYMBOL(kthread_bind); +/** + * kthread_stop - stop a thread created by kthread_create(). + * @k: thread created by kthread_create(). + * + * Sets kthread_should_stop() for @k to return true, wakes it, and + * waits for it to exit. Your threadfn() must not call do_exit() + * itself if you use this function! This can also be called after + * kthread_create() instead of calling wake_up_process(): the thread + * will exit without calling threadfn(). + * + * Returns the result of threadfn(), or %-EINTR if wake_up_process() + * was never called. + */ int kthread_stop(struct task_struct *k) { int ret; - down(&kthread_stop_lock); + mutex_lock(&kthread_stop_lock); /* It could exit after stop_info.k set, but before wake_up_process. */ get_task_struct(k); /* Must init completion *before* thread sees kthread_stop_info.k */ init_completion(&kthread_stop_info.done); - wmb(); + smp_wmb(); /* Now set kthread_should_stop() to true, and wake it up. */ kthread_stop_info.k = k; @@ -178,8 +239,18 @@ int kthread_stop(struct task_struct *k) wait_for_completion(&kthread_stop_info.done); kthread_stop_info.k = NULL; ret = kthread_stop_info.err; - up(&kthread_stop_lock); + mutex_unlock(&kthread_stop_lock); return ret; } EXPORT_SYMBOL(kthread_stop); + +static __init int helper_init(void) +{ + helper_wq = create_singlethread_workqueue("kthread"); + BUG_ON(!helper_wq); + + return 0; +} + +core_initcall(helper_init);