Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754456Ab3IPGiY (ORCPT ); Mon, 16 Sep 2013 02:38:24 -0400 Received: from ozlabs.org ([203.10.76.45]:60004 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750870Ab3IPGiW (ORCPT ); Mon, 16 Sep 2013 02:38:22 -0400 From: Rusty Russell To: Lucas De Marchi Cc: Peter Chen , lkml Subject: Re: [RFC PATCH 1/1] module: Make wait module's refcount to zero procedure as async In-Reply-To: References: <1378955676-12708-1-git-send-email-peter.chen@freescale.com> <87ioy536mu.fsf@rustcorp.com.au> User-Agent: Notmuch/0.15.2+81~gd2c8818 (http://notmuchmail.org) Emacs/23.4.1 (i686-pc-linux-gnu) Date: Mon, 16 Sep 2013 13:17:16 +0930 Message-ID: <87wqmh1l8b.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5148 Lines: 163 Lucas De Marchi writes: > On Thu, Sep 12, 2013 at 9:30 PM, Rusty Russell wrote: >> Peter Chen writes: >>> Currently, if module's refcount is not zero during the unload, >>> it waits there until the user decreases that refcount. >> >> Hi Peter, >> >> In practice userspace uses O_NONBLOCK. In fact, I've been >> thinking of removing the blocking case altogether, since it's not really >> what people want. >> >> That would solve your problem and make the code simpler. Thoughts? > > I'm all in favor of this. It's been almost 1 year it's deprecated in > kmod and if anyone tries to use we force a 10s delay on module > removal. So far nobody complained. > > Lucas De Marchi Here's what I've got in my pending-rebases tree. Cheers, Rusty. module: remove rmmod --wait option. The option to wait for a module reference count to reach zero was in the initial module implementation, but it was never supported in modprobe (you had to use rmmod --wait). After discussion with Lucas, It has been deprecated (with a 10 second sleep) in kmod for the last year. This finally removes it: the flag will evoke a printk warning and a normal (non-blocking) remove attempt. Cc: Lucas De Marchi Signed-off-by: Rusty Russell diff --git a/include/linux/module.h b/include/linux/module.h index 05f2447..15cd6b1 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -367,9 +367,6 @@ struct module /* What modules do I depend on? */ struct list_head target_list; - /* Who is waiting for us to be unloaded */ - struct task_struct *waiter; - /* Destruction function. */ void (*exit)(void); diff --git a/kernel/module.c b/kernel/module.c index dc58274..947105f 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -644,8 +644,6 @@ static int module_unload_init(struct module *mod) /* Hold reference count during initialization. */ __this_cpu_write(mod->refptr->incs, 1); - /* Backwards compatibility macros put refcount during init. */ - mod->waiter = current; return 0; } @@ -771,16 +769,9 @@ static int __try_stop_module(void *_sref) static int try_stop_module(struct module *mod, int flags, int *forced) { - if (flags & O_NONBLOCK) { - struct stopref sref = { mod, flags, forced }; + struct stopref sref = { mod, flags, forced }; - return stop_machine(__try_stop_module, &sref, NULL); - } else { - /* We don't need to stop the machine for this. */ - mod->state = MODULE_STATE_GOING; - synchronize_sched(); - return 0; - } + return stop_machine(__try_stop_module, &sref, NULL); } unsigned long module_refcount(struct module *mod) @@ -813,21 +804,6 @@ EXPORT_SYMBOL(module_refcount); /* This exists whether we can unload or not */ static void free_module(struct module *mod); -static void wait_for_zero_refcount(struct module *mod) -{ - /* Since we might sleep for some time, release the mutex first */ - mutex_unlock(&module_mutex); - for (;;) { - pr_debug("Looking at refcount...\n"); - set_current_state(TASK_UNINTERRUPTIBLE); - if (module_refcount(mod) == 0) - break; - schedule(); - } - current->state = TASK_RUNNING; - mutex_lock(&module_mutex); -} - SYSCALL_DEFINE2(delete_module, const char __user *, name_user, unsigned int, flags) { @@ -842,6 +818,11 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, return -EFAULT; name[MODULE_NAME_LEN-1] = '\0'; + if (!(flags & O_NONBLOCK)) { + printk(KERN_WARNING + "waiting module removal not supported: please upgrade"); + } + if (mutex_lock_interruptible(&module_mutex) != 0) return -EINTR; @@ -859,8 +840,7 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, /* Doing init or already dying? */ if (mod->state != MODULE_STATE_LIVE) { - /* FIXME: if (force), slam module count and wake up - waiter --RR */ + /* FIXME: if (force), slam module count damn the torpedoes */ pr_debug("%s already dying\n", mod->name); ret = -EBUSY; goto out; @@ -876,18 +856,11 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, } } - /* Set this up before setting mod->state */ - mod->waiter = current; - /* Stop the machine so refcounts can't move and disable module. */ ret = try_stop_module(mod, flags, &forced); if (ret != 0) goto out; - /* Never wait if forced. */ - if (!forced && module_refcount(mod) != 0) - wait_for_zero_refcount(mod); - mutex_unlock(&module_mutex); /* Final destruction now no one is using it. */ if (mod->exit != NULL) @@ -1005,9 +978,6 @@ void module_put(struct module *module) __this_cpu_inc(module->refptr->decs); trace_module_put(module, _RET_IP_); - /* Maybe they're waiting for us to drop reference? */ - if (unlikely(!module_is_live(module))) - wake_up_process(module->waiter); preempt_enable(); } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/