From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7408ECAAD3 for ; Wed, 14 Sep 2022 22:57:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229824AbiINW5I (ORCPT ); Wed, 14 Sep 2022 18:57:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229772AbiINW5A (ORCPT ); Wed, 14 Sep 2022 18:57:00 -0400 Received: from mail-pl1-f175.google.com (mail-pl1-f175.google.com [209.85.214.175]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E969083059; Wed, 14 Sep 2022 15:56:58 -0700 (PDT) Received: by mail-pl1-f175.google.com with SMTP id l10so16568348plb.10; Wed, 14 Sep 2022 15:56:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date; bh=hIeIUTsBV4QxjBZVDpe2dp3qI8fehLgRx48IHpHPzW8=; b=wdIrNcyTufCnLE2MrarhWcgNI47ziV7uNfT9DSr4fNIANC8H59e3bIu4qvfIjcaOmS 9w27RE8tuYJEGH6jqrrbqSN7++hKQJQ7+muFaEPzS3pJ0Ap1kqihckqKZ/OlB9IgaH7J wNudswNnMFHg+EjA0AkgCbGsf231t+qvtoxX5lVEECfK9wkqPYplQpga6lr87jL1/wus cSSOINTUHvtavMGymA440x9VbPvgxUuKVymo+AfRiT6/6+JPsXnEvxPYcOQxxrV6Bghn YZYzLq3Wp3+FRTcyr9XpORH79uc+mxG9UVWE3sqRh0PkTYWRPaBTu3ej+zDidPw7lg5x Uo8Q== X-Gm-Message-State: ACrzQf0ammYT0b7vP2LZwSdp16c61gRQQqUJ9UILsgELsigOJLjqwh6o Zknmx938O9syRXCWVxtjCao= X-Google-Smtp-Source: AMsMyM7xbb0K/O3zh7pzBk0SS0ANyvZ/W2+59zP+9cC7ZtIfUPFv4j7NqiRjg9PlRZ0Cr9vyvQoM7g== X-Received: by 2002:a17:90b:b06:b0:200:aff0:2e68 with SMTP id bf6-20020a17090b0b0600b00200aff02e68mr7411578pjb.159.1663196218342; Wed, 14 Sep 2022 15:56:58 -0700 (PDT) Received: from bvanassche-linux.mtv.corp.google.com ([2620:15c:211:201:9147:e0c1:9227:cf53]) by smtp.gmail.com with ESMTPSA id w9-20020a170902d70900b0016d1b70872asm2606926ply.134.2022.09.14.15.56.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Sep 2022 15:56:57 -0700 (PDT) From: Bart Van Assche To: "Martin K . Petersen" Cc: linux-scsi@vger.kernel.org, Bart Van Assche , Luis Chamberlain , Christoph Hellwig , Ming Lei , Hannes Reinecke , John Garry , Mike Christie , Krzysztof Kozlowski , Greg Kroah-Hartman , linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org, "James E.J. Bottomley" , Tejun Heo Subject: [PATCH v5 6/7] module: Improve support for asynchronous module exit code Date: Wed, 14 Sep 2022 15:56:20 -0700 Message-Id: <20220914225621.415631-7-bvanassche@acm.org> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog In-Reply-To: <20220914225621.415631-1-bvanassche@acm.org> References: <20220914225621.415631-1-bvanassche@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: Some kernel modules call device_del() from their module exit code and schedule asynchronous work from inside the .release callback without waiting until that callback has finished. As an example, many SCSI LLD drivers call scsi_remove_host() from their module exit code. scsi_remove_host() may invoke scsi_device_dev_release_usercontext() asynchronously. scsi_device_dev_release_usercontext() uses the host template pointer and that pointer usually exists in static storage in the SCSI LLD. Support using the module reference count to keep the module around until asynchronous module exiting has completed by waiting in the delete_module() system call until the module reference count drops to zero. The following debug patch has been used to make the new wait_event() call wait: diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 8be8e08fb67d..fead694ff95a 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -518,6 +519,7 @@ static void scsi_device_dev_release_usercontext(struct work_struct *work) if (parent) put_device(parent); + msleep(100); module_put(mod); } diff --git a/kernel/module/main.c b/kernel/module/main.c index a271126d7d59..0bf75ec3f5a8 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -756,8 +756,10 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, * unloading is not forced, wait for the module reference count to drop * to zero again. */ - if (!forced) + if (!forced) { + WARN_ON_ONCE(atomic_read(&mod->refcnt)); wait_event(mod->refcnt_wq, atomic_read(&mod->refcnt) == 0); + } blocking_notifier_call_chain(&module_notify_list, MODULE_STATE_GOING, mod); klp_module_going(mod); diff --git a/kernel/workqueue.c b/kernel/workqueue.c index aeea9731ef80..f021625f2caa 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3355,7 +3355,7 @@ int schedule_on_each_cpu(work_func_t func) */ int execute_in_process_context(work_func_t fn, struct execute_work *ew) { - if (!in_interrupt()) { + if (false && !in_interrupt()) { fn(&ew->work); return 0; } Cc: Luis Chamberlain Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: John Garry Cc: Mike Christie Cc: Krzysztof Kozlowski Cc: Greg Kroah-Hartman Cc: linux-modules@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Bart Van Assche --- include/linux/module.h | 1 + kernel/module/main.c | 10 ++++++++++ 2 files changed, 11 insertions(+) diff --git a/include/linux/module.h b/include/linux/module.h index 518296ea7f73..3a77d2bd4198 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -533,6 +533,7 @@ struct module { /* Destruction function. */ void (*exit)(void); + wait_queue_head_t refcnt_wq; atomic_t refcnt; #endif diff --git a/kernel/module/main.c b/kernel/module/main.c index a4e4d84b6f4e..a271126d7d59 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -550,6 +550,7 @@ static int module_unload_init(struct module *mod) /* Hold reference count during initialization. */ atomic_inc(&mod->refcnt); + init_waitqueue_head(&mod->refcnt_wq); return 0; } @@ -750,6 +751,13 @@ SYSCALL_DEFINE2(delete_module, const char __user *, name_user, /* Final destruction now no one is using it. */ if (mod->exit != NULL) mod->exit(); + /* + * If the module reference count was increased by mod->exit() and if + * unloading is not forced, wait for the module reference count to drop + * to zero again. + */ + if (!forced) + wait_event(mod->refcnt_wq, atomic_read(&mod->refcnt) == 0); blocking_notifier_call_chain(&module_notify_list, MODULE_STATE_GOING, mod); klp_module_going(mod); @@ -854,6 +862,8 @@ void module_put(struct module *module) WARN_ON(ret < 0); /* Failed to put refcount */ trace_module_put(module, _RET_IP_); preempt_enable(); + if (ret == 0) + wake_up(&module->refcnt_wq); } } EXPORT_SYMBOL(module_put);