From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-891914-1520357761-2-16802037786012209585 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES enfr, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=gsCl=F4=gmail.com=htejun@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520357760; b=EOqEavttqvW2cDXZraPCsSRw20zM8kJ3MXSe26aj5omRG1I LbmnjdJKi6/WmPlZRogQnUseYwz6ISCA5Pxg9ACHVlTU6tqLebNxpvhOxOkK4hZH 21DbRKw+vaZaXf2XwcGvaWiGRu2c/SqNqwQgorJEuSkVYorDPkL0uOIbU9SD8+wo Jhi3HBbnvQlH2eX4jpT7iqrYubCN2PvFb17Hx7rxoYnDU0ERn4707w8FBR7bytlX YozOLJXEwkY2V4t+AnrW1BGD9k9kQnD43acRSPUHpQbx3HGQQ+abN/v7KP0UNQPd kRE+gHIVB4LhjZaHA+hEeopDli4Dbzg6QQ+J7kA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=sender:from:to:cc:subject:date:message-id :in-reply-to:references; s=arctest; t=1520357760; bh=YyBmo4kInCj 52a9l6TvxOFqF/cRoHG/Cke3iQ6kgzvI=; b=NNqVogjD+R1KEZs6TlcPdQ1xQW5 yzHsrS1e3wJszx10M17iT7IjJSWuwMNnEkM1tgAbte0ov/ROjTwFS0Smgv9itKEW vdSEiCvVXQ687vyWKaSFzhBJz6ux4NyYyxzee4N61MF3i0yBidHJ6aS7ELEb+Vk0 wgxrkWT6LlaGhK3siyBkwlBM15FrhagtjAsEEJwNf2qsg33dBdf2dNFdHywnRSWR 64lAnc7kiqcCTwSTYMOZz6x0a7p4DYPtjSsy2AWwnnOE4w4EmC/RsvjqS8NBiONV jrL3GaxOndVm/KSkiUDCechfz4U8Cn8E3rGac2zHNugjWH9XO8s9+N2ggjQ== ARC-Authentication-Results: i=1; mx2.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=O+EjZV1T x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=gsCl=F4=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=N64hqeEd; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx2.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=O+EjZV1T x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=gsCl=F4=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=0 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=N64hqeEd; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC93C20856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=htejun@gmail.com X-Google-Smtp-Source: AG47ELsSUJQcurjEmGgSkNKPOVGNtN5b2QuNr2nibg9LgAsUWQWkCJ6xkl32kMrHbf565eOCOy8scQ== Sender: Tejun Heo From: Tejun Heo To: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com Cc: security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Tejun Heo Subject: [PATCH 7/7] RCU, workqueue: Implement rcu_work Date: Tue, 6 Mar 2018 09:33:16 -0800 Message-Id: <20180306173316.3088458-7-tj@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20180306173316.3088458-1-tj@kernel.org> References: <20180306172657.3060270-1-tj@kernel.org> <20180306173316.3088458-1-tj@kernel.org> X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: There are cases where RCU callback needs to be bounced to a sleepable context. This is currently done by the RCU callback queueing a work item, which can be cumbersome to write and confusing to read. This patch introduces rcu_work, a workqueue work variant which gets executed after a RCU grace period, and converts the open coded bouncing in fs/aio and kernel/cgroup. v2: Use rcu_barrier() instead of synchronize_rcu() to wait for completion of previously queued rcu callback as per Paul. Signed-off-by: Tejun Heo Cc: "Paul E. McKenney" Cc: Linus Torvalds --- fs/aio.c | 21 +++++------------- include/linux/cgroup-defs.h | 2 +- include/linux/workqueue.h | 38 +++++++++++++++++++++++++++++++ kernel/cgroup/cgroup.c | 21 ++++++------------ kernel/workqueue.c | 54 +++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 106 insertions(+), 30 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 6bcd3fb..88d7927 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -115,8 +115,7 @@ struct kioctx { struct page **ring_pages; long nr_pages; - struct rcu_head free_rcu; - struct work_struct free_work; /* see free_ioctx() */ + struct rcu_work free_rwork; /* see free_ioctx() */ /* * signals when all in-flight requests are done @@ -592,13 +591,12 @@ static int kiocb_cancel(struct aio_kiocb *kiocb) /* * free_ioctx() should be RCU delayed to synchronize against the RCU * protected lookup_ioctx() and also needs process context to call - * aio_free_ring(), so the double bouncing through kioctx->free_rcu and - * ->free_work. + * aio_free_ring(). Use rcu_work. */ static void free_ioctx(struct work_struct *work) { - struct kioctx *ctx = container_of(work, struct kioctx, free_work); - + struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx, + free_rwork); pr_debug("freeing %p\n", ctx); aio_free_ring(ctx); @@ -608,14 +606,6 @@ static void free_ioctx(struct work_struct *work) kmem_cache_free(kioctx_cachep, ctx); } -static void free_ioctx_rcufn(struct rcu_head *head) -{ - struct kioctx *ctx = container_of(head, struct kioctx, free_rcu); - - INIT_WORK(&ctx->free_work, free_ioctx); - schedule_work(&ctx->free_work); -} - static void free_ioctx_reqs(struct percpu_ref *ref) { struct kioctx *ctx = container_of(ref, struct kioctx, reqs); @@ -625,7 +615,8 @@ static void free_ioctx_reqs(struct percpu_ref *ref) complete(&ctx->rq_wait->comp); /* Synchronize against RCU protected table->table[] dereferences */ - call_rcu(&ctx->free_rcu, free_ioctx_rcufn); + INIT_RCU_WORK(&ctx->free_rwork, free_ioctx); + queue_rcu_work(system_wq, &ctx->free_rwork); } /* diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 9f242b8..92d7640 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -151,8 +151,8 @@ struct cgroup_subsys_state { atomic_t online_cnt; /* percpu_ref killing and RCU release */ - struct rcu_head rcu_head; struct work_struct destroy_work; + struct rcu_work destroy_rwork; /* * PI: the parent css. Placed here for cache proximity to following diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index bc0cda1..b39f3a4 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -13,6 +13,7 @@ #include #include #include +#include struct workqueue_struct; @@ -120,6 +121,15 @@ struct delayed_work { int cpu; }; +struct rcu_work { + struct work_struct work; + struct rcu_head rcu; + + /* target workqueue and CPU ->rcu uses to queue ->work */ + struct workqueue_struct *wq; + int cpu; +}; + /** * struct workqueue_attrs - A struct for workqueue attributes. * @@ -151,6 +161,11 @@ static inline struct delayed_work *to_delayed_work(struct work_struct *work) return container_of(work, struct delayed_work, work); } +static inline struct rcu_work *to_rcu_work(struct work_struct *work) +{ + return container_of(work, struct rcu_work, work); +} + struct execute_work { struct work_struct work; }; @@ -266,6 +281,12 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; } #define INIT_DEFERRABLE_WORK_ONSTACK(_work, _func) \ __INIT_DELAYED_WORK_ONSTACK(_work, _func, TIMER_DEFERRABLE) +#define INIT_RCU_WORK(_work, _func) \ + INIT_WORK(&(_work)->work, (_func)) + +#define INIT_RCU_WORK_ONSTACK(_work, _func) \ + INIT_WORK_ONSTACK(&(_work)->work, (_func)) + /** * work_pending - Find out whether a work item is currently pending * @work: The work item in question @@ -447,6 +468,8 @@ extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, struct delayed_work *work, unsigned long delay); extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay); +extern bool queue_rcu_work_on(int cpu, struct workqueue_struct *wq, + struct rcu_work *rwork); extern void flush_workqueue(struct workqueue_struct *wq); extern void drain_workqueue(struct workqueue_struct *wq); @@ -463,6 +486,8 @@ extern bool flush_delayed_work(struct delayed_work *dwork); extern bool cancel_delayed_work(struct delayed_work *dwork); extern bool cancel_delayed_work_sync(struct delayed_work *dwork); +extern bool flush_rcu_work(struct rcu_work *rwork); + extern void workqueue_set_max_active(struct workqueue_struct *wq, int max_active); extern struct work_struct *current_work(void); @@ -520,6 +545,19 @@ static inline bool mod_delayed_work(struct workqueue_struct *wq, } /** + * queue_rcu_work - queue work on a workqueue after a RCU grace period + * @wq: workqueue to use + * @rwork: RCU work to queue + * + * Equivalent to queue_rcu_work_on() but tries to use the local CPU. + */ +static inline bool queue_rcu_work(struct workqueue_struct *wq, + struct rcu_work *rwork) +{ + return queue_rcu_work_on(WORK_CPU_UNBOUND, wq, rwork); +} + +/** * schedule_work_on - put work task on a specific cpu * @cpu: cpu to put the work task on * @work: job to be done diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 8cda3bc..4c5d4ca0 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -4514,10 +4514,10 @@ static struct cftype cgroup_base_files[] = { * and thus involve punting to css->destroy_work adding two additional * steps to the already complex sequence. */ -static void css_free_work_fn(struct work_struct *work) +static void css_free_rwork_fn(struct work_struct *work) { - struct cgroup_subsys_state *css = - container_of(work, struct cgroup_subsys_state, destroy_work); + struct cgroup_subsys_state *css = container_of(to_rcu_work(work), + struct cgroup_subsys_state, destroy_rwork); struct cgroup_subsys *ss = css->ss; struct cgroup *cgrp = css->cgroup; @@ -4563,15 +4563,6 @@ static void css_free_work_fn(struct work_struct *work) } } -static void css_free_rcu_fn(struct rcu_head *rcu_head) -{ - struct cgroup_subsys_state *css = - container_of(rcu_head, struct cgroup_subsys_state, rcu_head); - - INIT_WORK(&css->destroy_work, css_free_work_fn); - queue_work(cgroup_destroy_wq, &css->destroy_work); -} - static void css_release_work_fn(struct work_struct *work) { struct cgroup_subsys_state *css = @@ -4621,7 +4612,8 @@ static void css_release_work_fn(struct work_struct *work) mutex_unlock(&cgroup_mutex); - call_rcu(&css->rcu_head, css_free_rcu_fn); + INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); + queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); } static void css_release(struct percpu_ref *ref) @@ -4755,7 +4747,8 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp, err_list_del: list_del_rcu(&css->sibling); err_free_css: - call_rcu(&css->rcu_head, css_free_rcu_fn); + INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn); + queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork); return ERR_PTR(err); } diff --git a/kernel/workqueue.c b/kernel/workqueue.c index bb9a519..e26c2f4 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1604,6 +1604,40 @@ bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, } EXPORT_SYMBOL_GPL(mod_delayed_work_on); +static void rcu_work_rcufn(struct rcu_head *rcu) +{ + struct rcu_work *rwork = container_of(rcu, struct rcu_work, rcu); + + /* read the comment in __queue_work() */ + local_irq_disable(); + __queue_work(rwork->cpu, rwork->wq, &rwork->work); + local_irq_enable(); +} + +/** + * queue_rcu_work_on - queue work on specific CPU after a RCU grace period + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @rwork: work to queue + * + * Return: %false if @work was already on a queue, %true otherwise. + */ +bool queue_rcu_work_on(int cpu, struct workqueue_struct *wq, + struct rcu_work *rwork) +{ + struct work_struct *work = &rwork->work; + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + rwork->wq = wq; + rwork->cpu = cpu; + call_rcu(&rwork->rcu, rcu_work_rcufn); + return true; + } + + return false; +} +EXPORT_SYMBOL(queue_rcu_work_on); + /** * worker_enter_idle - enter idle state * @worker: worker which is entering idle state @@ -3001,6 +3035,26 @@ bool flush_delayed_work(struct delayed_work *dwork) } EXPORT_SYMBOL(flush_delayed_work); +/** + * flush_rcu_work - wait for a rwork to finish executing the last queueing + * @rwork: the rcu work to flush + * + * Return: + * %true if flush_rcu_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_rcu_work(struct rcu_work *rwork) +{ + if (test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&rwork->work))) { + rcu_barrier(); + flush_work(&rwork->work); + return true; + } else { + return flush_work(&rwork->work); + } +} +EXPORT_SYMBOL(flush_rcu_work); + static bool __cancel_work(struct work_struct *work, bool is_dwork) { unsigned long flags; -- 2.9.5