Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932285Ab3E3OJG (ORCPT ); Thu, 30 May 2013 10:09:06 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:43081 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754666Ab3E3OI6 (ORCPT ); Thu, 30 May 2013 10:08:58 -0400 Message-ID: <51A75D76.5090700@canonical.com> Date: Thu, 30 May 2013 16:08:54 +0200 From: Maarten Lankhorst User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Inki Dae CC: "linux-kernel@vger.kernel.org" , linux-arch@vger.kernel.org, peterz@infradead.org, x86@kernel.org, DRI mailing list , "linaro-mm-sig@lists.linaro.org" , robclark@gmail.com, rostedt@goodmis.org, tglx@linutronix.de, mingo@elte.hu, "linux-media@vger.kernel.org" Subject: Re: [PATCH v4 2/4] mutex: add support for wound/wait style locks, v5 References: <20130528144420.4538.70725.stgit@patser> <20130528144839.4538.39821.stgit@patser> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5252 Lines: 189 Op 29-05-13 12:33, Inki Dae schreef: > Hi, > > Just minor comments > > +Usage >> +----- >> + >> +Three different ways to acquire locks within the same w/w class. Common >> +definitions for methods #1 and #2: >> + >> +static DEFINE_WW_CLASS(ww_class); >> + >> +struct obj { >> + struct ww_mutex lock; >> + /* obj data */ >> +}; >> + >> +struct obj_entry { >> + struct list_head *list; >> + struct obj *obj; >> +}; >> + >> +Method 1, using a list in execbuf->buffers that's not allowed to be >> reordered. >> +This is useful if a list of required objects is already tracked somewhere. >> +Furthermore the lock helper can use propagate the -EALREADY return code >> back to >> +the caller as a signal that an object is twice on the list. This is >> useful if >> +the list is constructed from userspace input and the ABI requires >> userspace to >> +not have duplicate entries (e.g. for a gpu commandbuffer submission >> ioctl). >> + >> +int lock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) >> +{ >> + struct obj *res_obj = NULL; >> + struct obj_entry *contended_entry = NULL; >> + struct obj_entry *entry; >> + >> + ww_acquire_init(ctx, &ww_class); >> + >> +retry: >> + list_for_each_entry (list, entry) { >> + if (entry == res_obj) { >> Indeed, documentation was wrong. With the below diff it should almost compile now. I really don't want to know if it really does, it's meant to be documentation! diff --git a/Documentation/ww-mutex-design.txt b/Documentation/ww-mutex-design.txt index 8bd1761..379739c 100644 --- a/Documentation/ww-mutex-design.txt +++ b/Documentation/ww-mutex-design.txt @@ -100,7 +100,7 @@ struct obj { }; struct obj_entry { - struct list_head *list; + struct list_head head; struct obj *obj; }; @@ -120,14 +120,14 @@ int lock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) ww_acquire_init(ctx, &ww_class); retry: - list_for_each_entry (list, entry) { - if (entry == res_obj) { + list_for_each_entry (entry, list, head) { + if (entry->obj == res_obj) { res_obj = NULL; continue; } ret = ww_mutex_lock(&entry->obj->lock, ctx); if (ret < 0) { - contended_obj = entry; + contended_entry = entry; goto err; } } @@ -136,7 +136,7 @@ retry: return 0; err: - list_for_each_entry_continue_reverse (list, contended_entry, entry) + list_for_each_entry_continue_reverse (entry, list, head) ww_mutex_unlock(&entry->obj->lock); if (res_obj) @@ -163,13 +163,13 @@ int lock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) ww_acquire_init(ctx, &ww_class); - list_for_each_entry (list, entry) { + list_for_each_entry (entry, list, head) { ret = ww_mutex_lock(&entry->obj->lock, ctx); if (ret < 0) { entry2 = entry; - list_for_each_entry_continue_reverse (list, entry2) - ww_mutex_unlock(&entry->obj->lock); + list_for_each_entry_continue_reverse (entry2, list, head) + ww_mutex_unlock(&entry2->obj->lock); if (ret != -EDEADLK) { ww_acquire_fini(ctx); @@ -184,8 +184,8 @@ int lock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) * buf->next to the first unlocked entry, * restarting the for loop. */ - list_del(&entry->list); - list_add(&entry->list, list); + list_del(&entry->head); + list_add(&entry->head, list); } } @@ -199,7 +199,7 @@ void unlock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) { struct obj_entry *entry; - list_for_each_entry (list, entry) + list_for_each_entry (entry, list, head) ww_mutex_unlock(&entry->obj->lock); ww_acquire_fini(ctx); @@ -244,22 +244,21 @@ struct obj { static DEFINE_WW_CLASS(ww_class); -void __unlock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) +void __unlock_objs(struct list_head *list) { - struct obj entry; + struct obj *entry, *temp; - for_each_safe (list, entry) { + list_for_each_entry_safe (entry, temp, list, locked_list) { /* need to do that before unlocking, since only the current lock holder is allowed to use object */ - list_del(entry->locked_list); + list_del(&entry->locked_list); ww_mutex_unlock(entry->ww_mutex) } } void lock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) { - struct list_head locked_buffers; - struct obj obj = NULL, entry; + struct obj *obj; ww_acquire_init(ctx, &ww_class); @@ -275,15 +274,15 @@ retry: continue; } if (ret == -EDEADLK) { - __unlock_objs(list, ctx); + __unlock_objs(list); ww_mutex_lock_slow(obj, ctx); - list_add(locked_buffers, entry->locked_list); + list_add(&entry->locked_list, list); goto retry; } /* locked a new object, add it to the list */ - list_add(locked_buffers, entry->locked_list); + list_add_tail(&entry->locked_list, list); } ww_acquire_done(ctx); @@ -292,7 +291,7 @@ retry: void unlock_objs(struct list_head *list, struct ww_acquire_ctx *ctx) { - __unlock_objs(list, ctx); + __unlock_objs(list); ww_acquire_fini(ctx); } -- 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/