From: Josh Poimboeuf <jpoimboe@redhat.com> To: Petr Mladek <pmladek@suse.com> Cc: Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>, Jason Baron <jbaron@akamai.com>, Joe Lawrence <joe.lawrence@redhat.com>, Evgenii Shatokhin <eshatokhin@virtuozzo.com>, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v13 06/12] livepatch: Simplify API by removing registration step Date: Wed, 17 Oct 2018 14:06:57 -0500 Message-ID: <20181017190657.dv3kwx467brzhdnz@treble> (raw) In-Reply-To: <20181015123713.25868-7-pmladek@suse.com> On Mon, Oct 15, 2018 at 02:37:07PM +0200, Petr Mladek wrote: > @@ -319,96 +316,66 @@ forced it is guaranteed that no task sleeps or runs in the old code. > 5. Livepatch life-cycle > ======================= > > -Livepatching defines four basic operations that define the life cycle of each > -live patch: registration, enabling, disabling and unregistration. There are > -several reasons why it is done this way. > +Livepatches get automatically enabled when the respective module is loaded. (only true if the module enables the patch in its init function) > @@ -502,6 +483,9 @@ static void klp_free_objects(struct klp_patch *patch) > } > > /* > + * The synchronous variant is needed when the patch is freed in > + * the klp_enable_patch() error paths. > + * Hm? This comment seems confusingly out of context. > @@ -528,6 +512,23 @@ static void klp_free_patch_finish(struct klp_patch *patch) > kobject_put(&patch->kobj); > wait_for_completion(&patch->finish); > } > + > + /* Put the module after the last access to struct klp_patch. */ > + if (patch->module_put) > + module_put(patch->mod); > +} > + > +/* > + * The livepatch might be freed from sysfs interface created by the patch. > + * This work allows to wait until the interface is destroyed in a separate > + * context. > + */ > +static void klp_free_patch_fn(struct work_struct *work) To clarify that it's a work function, how about calling it "klp_free_patch_work_fn"? > static int klp_init_func(struct klp_object *obj, struct klp_func *func) > @@ -642,116 +643,38 @@ static int klp_init_patch(struct klp_patch *patch) > struct klp_object *obj; > int ret; > > - if (!patch->objs) > - return -EINVAL; > - > - mutex_lock(&klp_mutex); > - > patch->enabled = false; > - patch->forced = false; > + patch->module_put = false; > INIT_LIST_HEAD(&patch->list); > + INIT_WORK(&patch->free_work, klp_free_patch_fn); > init_completion(&patch->finish); > > + if (!patch->objs) > + return -EINVAL; > + > + /* > + * A reference is taken on the patch module to prevent it from being > + * unloaded. > + */ > + if (!try_module_get(patch->mod)) > + return -ENODEV; This comment isn't needed. It describes what try_module_get() does, which is common kernel knowledge. > + patch->module_put = true; The naming and semantics of the 'module_put' field are a little confusing. It's false in two cases: 1) try_module_get() failure 2) forced patch Maybe we can get rid of the need for the first case by moving the try_module_get() call to klp_enable_patch(), before calling klp_init_lists(). Then klp_free_patch_finish() will always be called with a module reference, so it doesn't have to check the 'module_put' field. We'd still need it for the force case, but then it can just be called 'forced' again. > --- a/samples/livepatch/livepatch-callbacks-demo.c > +++ b/samples/livepatch/livepatch-callbacks-demo.c > @@ -184,22 +184,11 @@ static struct klp_patch patch = { > > static int livepatch_callbacks_demo_init(void) > { > - int ret; > - > - ret = klp_register_patch(&patch); > - if (ret) > - return ret; > - ret = klp_enable_patch(&patch); > - if (ret) { > - WARN_ON(klp_unregister_patch(&patch)); > - return ret; > - } > - return 0; > + return klp_enable_patch(&patch); > } > > static void livepatch_callbacks_demo_exit(void) > { > - WARN_ON(klp_unregister_patch(&patch)); > } This module exit function is no longer needed. > > module_init(livepatch_callbacks_demo_init); > diff --git a/samples/livepatch/livepatch-sample.c b/samples/livepatch/livepatch-sample.c > index de30d1ba4791..88afb708a48d 100644 > --- a/samples/livepatch/livepatch-sample.c > +++ b/samples/livepatch/livepatch-sample.c > @@ -66,22 +66,11 @@ static struct klp_patch patch = { > > static int livepatch_init(void) > { > - int ret; > - > - ret = klp_register_patch(&patch); > - if (ret) > - return ret; > - ret = klp_enable_patch(&patch); > - if (ret) { > - WARN_ON(klp_unregister_patch(&patch)); > - return ret; > - } > - return 0; > + return klp_enable_patch(&patch); > } > > static void livepatch_exit(void) > { > - WARN_ON(klp_unregister_patch(&patch)); > } Ditto. -- Josh
next prev parent reply index Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-10-15 12:37 [PATCH v13 00/12] livepatch: Atomic replace feature Petr Mladek 2018-10-15 12:37 ` [PATCH v13 01/12] livepatch: Change void *new_func -> unsigned long new_addr in struct klp_func Petr Mladek 2018-10-15 12:37 ` [PATCH v13 02/12] livepatch: Helper macros to define livepatch structures Petr Mladek 2018-10-17 18:17 ` Josh Poimboeuf 2018-10-18 11:11 ` Petr Mladek 2018-10-18 12:58 ` Josh Poimboeuf 2018-10-24 11:28 ` Petr Mladek 2018-11-21 12:17 ` Miroslav Benes 2018-10-15 12:37 ` [PATCH v13 03/12] livepatch: Shuffle klp_enable_patch()/klp_disable_patch() code Petr Mladek 2018-10-15 12:37 ` [PATCH v13 04/12] livepatch: Consolidate klp_free functions Petr Mladek 2018-10-17 18:22 ` Josh Poimboeuf 2018-10-18 11:40 ` Petr Mladek 2018-11-21 13:59 ` Miroslav Benes 2018-11-21 14:40 ` Petr Mladek 2018-10-15 12:37 ` [PATCH v13 05/12] livepatch: Refuse to unload only livepatches available during a forced transition Petr Mladek 2018-10-17 18:35 ` Josh Poimboeuf 2018-10-18 12:09 ` Petr Mladek 2018-10-18 13:00 ` Josh Poimboeuf 2018-10-15 12:37 ` [PATCH v13 06/12] livepatch: Simplify API by removing registration step Petr Mladek 2018-10-17 19:06 ` Josh Poimboeuf [this message] 2018-10-18 12:33 ` Petr Mladek 2018-10-15 12:37 ` [PATCH v13 07/12] livepatch: Use lists to manage patches, objects and functions Petr Mladek 2018-10-17 20:31 ` Josh Poimboeuf 2018-10-18 12:34 ` Petr Mladek 2018-10-15 12:37 ` [PATCH v13 08/12] livepatch: Add atomic replace Petr Mladek 2018-11-23 12:00 ` Miroslav Benes 2018-10-15 12:37 ` [PATCH v13 09/12] livepatch: Remove Nop structures when unused Petr Mladek 2018-10-17 20:48 ` Josh Poimboeuf 2018-10-18 12:40 ` Petr Mladek 2018-10-15 12:37 ` [PATCH v13 10/12] livepatch: Atomic replace and cumulative patches documentation Petr Mladek 2018-10-15 12:37 ` [PATCH v13 11/12] livepatch: Remove ordering and refuse loading conflicting patches Petr Mladek 2018-10-15 12:37 ` [PATCH v13 12/12] selftests/livepatch: introduce tests Petr Mladek 2018-10-15 19:46 ` Joe Lawrence 2018-10-17 20:48 ` Josh Poimboeuf 2018-10-18 13:34 ` [PATCH v13 00/12] livepatch: Atomic replace feature Josh Poimboeuf
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