From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Date: Sun, 7 Apr 2019 15:46:13 +0000 Message-ID: <20190407154613.GA2770@localhost> References: <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com> <20190402152334.GC4102@linux.ibm.com> <161156422.1435.1554219247444.JavaMail.zimbra@efficios.com> <20190403133243.GE4102@linux.ibm.com> <1028306587.504.1554301662374.JavaMail.zimbra@efficios.com> <20190403162039.GA14111@linux.ibm.com> <20190405232835.GA24702@linux.ibm.com> <20190406230613.GA187766@google.com> <20190407133941.GC14111@linux.ibm.com> <20190407135937.GA30053@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190407135937.GA30053-tEXmvtCZX7AybS5Ee8rs3A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: "Paul E. McKenney" Cc: David Howells , amd-gfx , Thomas Gleixner , linux-nvdimm , Peter Zijlstra , fweisbec , dri-devel , Lai Jiangshan , linux-kernel , rostedt , Josh Triplett , rcu , Eric Dumazet , Mathieu Desnoyers , Oleg Nesterov , dipankar , Andrew Morton , Ingo Molnar List-Id: linux-nvdimm@lists.01.org On Sun, Apr 07, 2019 at 06:59:37AM -0700, Paul E. McKenney wrote: > On Sun, Apr 07, 2019 at 06:39:41AM -0700, Paul E. McKenney wrote: > > On Sat, Apr 06, 2019 at 07:06:13PM -0400, Joel Fernandes wrote: > > [ . . . ] > > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > > > index f8f6f04c4453..c2d919a1566e 100644 > > > > --- a/include/asm-generic/vmlinux.lds.h > > > > +++ b/include/asm-generic/vmlinux.lds.h > > > > @@ -338,6 +338,10 @@ > > > > KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ > > > > __stop___tracepoints_ptrs = .; \ > > > > *(__tracepoints_strings)/* Tracepoints: strings */ \ > > > > + . = ALIGN(8); \ > > > > + __start___srcu_struct = .; \ > > > > + *(___srcu_struct_ptrs) \ > > > > + __end___srcu_struct = .; \ > > > > } \ > > > > > > This vmlinux linker modification is not needed. I tested without it and srcu > > > torture works fine with rcutorture built as a module. Putting further prints > > > in kernel/module.c verified that the kernel is able to find the srcu structs > > > just fine. You could squash the below patch into this one or apply it on top > > > of the dev branch. > > > > Good point, given that otherwise FORTRAN named common blocks would not > > work. > > > > But isn't one advantage of leaving that stuff in the RO_DATA_SECTION() > > macro that it can be mapped read-only? Or am I suffering from excessive > > optimism? > > And to answer the other question, in the case where I am suffering from > excessive optimism, it should be a separate commit. Please see below > for the updated original commit thus far. > Actually the vmlinux.lds.h file is unused for module building. For ex, if you delete include/asm-generic/vmlinux.lds.h , then you can still build rcutorture.ko. Did I miss something obvious? In that case the vmlinux.lds.h are not needed since the __section annotations automatically place the srcu structs in a separate section. Let me know if you would like me to send a patch separately, or if the appended patch for the same in my previous email suffices. > And may I have your Tested-by? Absolutely, please do and thanks! - Joel > Thanx, Paul > > ------------------------------------------------------------------------ > > commit a365bb5f6eafb220a1448674054b05c250829313 > Author: Paul E. McKenney > Date: Fri Apr 5 16:15:00 2019 -0700 > > srcu: Allocate per-CPU data for DEFINE_SRCU() in modules > > Adding DEFINE_SRCU() or DEFINE_STATIC_SRCU() to a loadable module requires > that the size of the reserved region be increased, which is not something > we want to be doing all that often. One approach would be to require > that loadable modules define an srcu_struct and invoke init_srcu_struct() > from their module_init function and cleanup_srcu_struct() from their > module_exit function. However, this is more than a bit user unfriendly. > > This commit therefore creates an ___srcu_struct_ptrs linker section, > and pointers to srcu_struct structures created by DEFINE_SRCU() and > DEFINE_STATIC_SRCU() within a module are placed into that module's > ___srcu_struct_ptrs section. The required init_srcu_struct() and > cleanup_srcu_struct() functions are then automatically invoked as needed > when that module is loaded and unloaded, thus allowing modules to continue > to use DEFINE_SRCU() and DEFINE_STATIC_SRCU() while avoiding the need > to increase the size of the reserved region. > > Many of the algorithms and some of the code was cheerfully cherry-picked > from other code making use of linker sections, perhaps most notably from > tracepoints. All bugs are nevertheless the sole property of the author. > > Suggested-by: Mathieu Desnoyers > [ paulmck: Use __section() and use "default" in srcu_module_notify()'s > "switch" statement as suggested by Joel Fernandes. ] > Signed-off-by: Paul E. McKenney > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index f8f6f04c4453..c2d919a1566e 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -338,6 +338,10 @@ > KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ > __stop___tracepoints_ptrs = .; \ > *(__tracepoints_strings)/* Tracepoints: strings */ \ > + . = ALIGN(8); \ > + __start___srcu_struct = .; \ > + *(___srcu_struct_ptrs) \ > + __end___srcu_struct = .; \ > } \ > \ > .rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \ > diff --git a/include/linux/module.h b/include/linux/module.h > index 5bf5dcd91009..921443a026dd 100644 > --- a/include/linux/module.h > +++ b/include/linux/module.h > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -448,6 +449,10 @@ struct module { > unsigned int num_tracepoints; > tracepoint_ptr_t *tracepoints_ptrs; > #endif > +#ifdef CONFIG_TREE_SRCU > + unsigned int num_srcu_structs; > + struct srcu_struct **srcu_struct_ptrs; > +#endif > #ifdef CONFIG_BPF_EVENTS > unsigned int num_bpf_raw_events; > struct bpf_raw_event_map *bpf_raw_events; > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > index 7f7c8c050f63..8af1824c46a8 100644 > --- a/include/linux/srcutree.h > +++ b/include/linux/srcutree.h > @@ -120,9 +120,17 @@ struct srcu_struct { > * > * See include/linux/percpu-defs.h for the rules on per-CPU variables. > */ > -#define __DEFINE_SRCU(name, is_static) \ > - static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\ > - is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_data) > +#ifdef MODULE > +# define __DEFINE_SRCU(name, is_static) \ > + is_static struct srcu_struct name; \ > + struct srcu_struct *__srcu_struct_##name \ > + __section("___srcu_struct_ptrs") = &name > +#else > +# define __DEFINE_SRCU(name, is_static) \ > + static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ > + is_static struct srcu_struct name = \ > + __SRCU_STRUCT_INIT(name, name##_srcu_data) > +#endif > #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) > #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) > > diff --git a/kernel/module.c b/kernel/module.c > index 0b9aa8ab89f0..524da609c884 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3093,6 +3093,11 @@ static int find_module_sections(struct module *mod, struct load_info *info) > sizeof(*mod->tracepoints_ptrs), > &mod->num_tracepoints); > #endif > +#ifdef CONFIG_TREE_SRCU > + mod->srcu_struct_ptrs = section_objs(info, "___srcu_struct_ptrs", > + sizeof(*mod->srcu_struct_ptrs), > + &mod->num_srcu_structs); > +#endif > #ifdef CONFIG_BPF_EVENTS > mod->bpf_raw_events = section_objs(info, "__bpf_raw_tp_map", > sizeof(*mod->bpf_raw_events), > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index 9b761e546de8..2ded2614a2f4 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -1310,3 +1310,68 @@ void __init srcu_init(void) > queue_work(rcu_gp_wq, &ssp->work.work); > } > } > + > +#ifdef CONFIG_MODULES > + > +/* Initialize any global-scope srcu_struct structures used by this module. */ > +static int srcu_module_coming(struct module *mod) > +{ > + int i; > + struct srcu_struct **sspp = mod->srcu_struct_ptrs; > + int ret; > + > + for (i = 0; i < mod->num_srcu_structs; i++) { > + ret = init_srcu_struct(*(sspp++)); > + if (WARN_ON_ONCE(ret)) > + return ret; > + } > + return 0; > +} > + > +/* Clean up any global-scope srcu_struct structures used by this module. */ > +static void srcu_module_going(struct module *mod) > +{ > + int i; > + struct srcu_struct **sspp = mod->srcu_struct_ptrs; > + > + for (i = 0; i < mod->num_srcu_structs; i++) > + cleanup_srcu_struct(*(sspp++)); > +} > + > +/* Handle one module, either coming or going. */ > +static int srcu_module_notify(struct notifier_block *self, > + unsigned long val, void *data) > +{ > + struct module *mod = data; > + int ret = 0; > + > + switch (val) { > + case MODULE_STATE_COMING: > + ret = srcu_module_coming(mod); > + break; > + case MODULE_STATE_GOING: > + srcu_module_going(mod); > + break; > + default: > + break; > + } > + return ret; > +} > + > +static struct notifier_block srcu_module_nb = { > + .notifier_call = srcu_module_notify, > + .priority = 0, > +}; > + > +static __init int init_srcu_module_notifier(void) > +{ > + int ret; > + > + ret = register_module_notifier(&srcu_module_nb); > + if (ret) > + pr_warn("Failed to register srcu module notifier\n"); > + return ret; > +} > +late_initcall(init_srcu_module_notifier); > + > +#endif /* #ifdef CONFIG_MODULES */ > 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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DC61C282DD for ; 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[73.216.90.110]) by smtp.gmail.com with ESMTPSA id x15sm13712804qkh.13.2019.04.07.08.46.15 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 07 Apr 2019 08:46:15 -0700 (PDT) Date: Sun, 7 Apr 2019 15:46:13 +0000 From: Joel Fernandes To: "Paul E. McKenney" Cc: Mathieu Desnoyers , rcu , linux-kernel , Ingo Molnar , Lai Jiangshan , dipankar , Andrew Morton , Josh Triplett , Thomas Gleixner , Peter Zijlstra , rostedt , David Howells , Eric Dumazet , fweisbec , Oleg Nesterov , linux-nvdimm , dri-devel , amd-gfx Subject: Re: [PATCH RFC tip/core/rcu 0/4] Forbid static SRCU use in modules Message-ID: <20190407154613.GA2770@localhost> References: <886051277.1395.1554218080591.JavaMail.zimbra@efficios.com> <20190402152334.GC4102@linux.ibm.com> <161156422.1435.1554219247444.JavaMail.zimbra@efficios.com> <20190403133243.GE4102@linux.ibm.com> <1028306587.504.1554301662374.JavaMail.zimbra@efficios.com> <20190403162039.GA14111@linux.ibm.com> <20190405232835.GA24702@linux.ibm.com> <20190406230613.GA187766@google.com> <20190407133941.GC14111@linux.ibm.com> <20190407135937.GA30053@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190407135937.GA30053@linux.ibm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 07, 2019 at 06:59:37AM -0700, Paul E. McKenney wrote: > On Sun, Apr 07, 2019 at 06:39:41AM -0700, Paul E. McKenney wrote: > > On Sat, Apr 06, 2019 at 07:06:13PM -0400, Joel Fernandes wrote: > > [ . . . ] > > > > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > > > > index f8f6f04c4453..c2d919a1566e 100644 > > > > --- a/include/asm-generic/vmlinux.lds.h > > > > +++ b/include/asm-generic/vmlinux.lds.h > > > > @@ -338,6 +338,10 @@ > > > > KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ > > > > __stop___tracepoints_ptrs = .; \ > > > > *(__tracepoints_strings)/* Tracepoints: strings */ \ > > > > + . = ALIGN(8); \ > > > > + __start___srcu_struct = .; \ > > > > + *(___srcu_struct_ptrs) \ > > > > + __end___srcu_struct = .; \ > > > > } \ > > > > > > This vmlinux linker modification is not needed. I tested without it and srcu > > > torture works fine with rcutorture built as a module. Putting further prints > > > in kernel/module.c verified that the kernel is able to find the srcu structs > > > just fine. You could squash the below patch into this one or apply it on top > > > of the dev branch. > > > > Good point, given that otherwise FORTRAN named common blocks would not > > work. > > > > But isn't one advantage of leaving that stuff in the RO_DATA_SECTION() > > macro that it can be mapped read-only? Or am I suffering from excessive > > optimism? > > And to answer the other question, in the case where I am suffering from > excessive optimism, it should be a separate commit. Please see below > for the updated original commit thus far. > Actually the vmlinux.lds.h file is unused for module building. For ex, if you delete include/asm-generic/vmlinux.lds.h , then you can still build rcutorture.ko. Did I miss something obvious? In that case the vmlinux.lds.h are not needed since the __section annotations automatically place the srcu structs in a separate section. Let me know if you would like me to send a patch separately, or if the appended patch for the same in my previous email suffices. > And may I have your Tested-by? Absolutely, please do and thanks! - Joel > Thanx, Paul > > ------------------------------------------------------------------------ > > commit a365bb5f6eafb220a1448674054b05c250829313 > Author: Paul E. McKenney > Date: Fri Apr 5 16:15:00 2019 -0700 > > srcu: Allocate per-CPU data for DEFINE_SRCU() in modules > > Adding DEFINE_SRCU() or DEFINE_STATIC_SRCU() to a loadable module requires > that the size of the reserved region be increased, which is not something > we want to be doing all that often. One approach would be to require > that loadable modules define an srcu_struct and invoke init_srcu_struct() > from their module_init function and cleanup_srcu_struct() from their > module_exit function. However, this is more than a bit user unfriendly. > > This commit therefore creates an ___srcu_struct_ptrs linker section, > and pointers to srcu_struct structures created by DEFINE_SRCU() and > DEFINE_STATIC_SRCU() within a module are placed into that module's > ___srcu_struct_ptrs section. The required init_srcu_struct() and > cleanup_srcu_struct() functions are then automatically invoked as needed > when that module is loaded and unloaded, thus allowing modules to continue > to use DEFINE_SRCU() and DEFINE_STATIC_SRCU() while avoiding the need > to increase the size of the reserved region. > > Many of the algorithms and some of the code was cheerfully cherry-picked > from other code making use of linker sections, perhaps most notably from > tracepoints. All bugs are nevertheless the sole property of the author. > > Suggested-by: Mathieu Desnoyers > [ paulmck: Use __section() and use "default" in srcu_module_notify()'s > "switch" statement as suggested by Joel Fernandes. ] > Signed-off-by: Paul E. McKenney > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index f8f6f04c4453..c2d919a1566e 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -338,6 +338,10 @@ > KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ > __stop___tracepoints_ptrs = .; \ > *(__tracepoints_strings)/* Tracepoints: strings */ \ > + . = ALIGN(8); \ > + __start___srcu_struct = .; \ > + *(___srcu_struct_ptrs) \ > + __end___srcu_struct = .; \ > } \ > \ > .rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \ > diff --git a/include/linux/module.h b/include/linux/module.h > index 5bf5dcd91009..921443a026dd 100644 > --- a/include/linux/module.h > +++ b/include/linux/module.h > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -448,6 +449,10 @@ struct module { > unsigned int num_tracepoints; > tracepoint_ptr_t *tracepoints_ptrs; > #endif > +#ifdef CONFIG_TREE_SRCU > + unsigned int num_srcu_structs; > + struct srcu_struct **srcu_struct_ptrs; > +#endif > #ifdef CONFIG_BPF_EVENTS > unsigned int num_bpf_raw_events; > struct bpf_raw_event_map *bpf_raw_events; > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > index 7f7c8c050f63..8af1824c46a8 100644 > --- a/include/linux/srcutree.h > +++ b/include/linux/srcutree.h > @@ -120,9 +120,17 @@ struct srcu_struct { > * > * See include/linux/percpu-defs.h for the rules on per-CPU variables. > */ > -#define __DEFINE_SRCU(name, is_static) \ > - static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\ > - is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_data) > +#ifdef MODULE > +# define __DEFINE_SRCU(name, is_static) \ > + is_static struct srcu_struct name; \ > + struct srcu_struct *__srcu_struct_##name \ > + __section("___srcu_struct_ptrs") = &name > +#else > +# define __DEFINE_SRCU(name, is_static) \ > + static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ > + is_static struct srcu_struct name = \ > + __SRCU_STRUCT_INIT(name, name##_srcu_data) > +#endif > #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) > #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) > > diff --git a/kernel/module.c b/kernel/module.c > index 0b9aa8ab89f0..524da609c884 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3093,6 +3093,11 @@ static int find_module_sections(struct module *mod, struct load_info *info) > sizeof(*mod->tracepoints_ptrs), > &mod->num_tracepoints); > #endif > +#ifdef CONFIG_TREE_SRCU > + mod->srcu_struct_ptrs = section_objs(info, "___srcu_struct_ptrs", > + sizeof(*mod->srcu_struct_ptrs), > + &mod->num_srcu_structs); > +#endif > #ifdef CONFIG_BPF_EVENTS > mod->bpf_raw_events = section_objs(info, "__bpf_raw_tp_map", > sizeof(*mod->bpf_raw_events), > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index 9b761e546de8..2ded2614a2f4 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -1310,3 +1310,68 @@ void __init srcu_init(void) > queue_work(rcu_gp_wq, &ssp->work.work); > } > } > + > +#ifdef CONFIG_MODULES > + > +/* Initialize any global-scope srcu_struct structures used by this module. */ > +static int srcu_module_coming(struct module *mod) > +{ > + int i; > + struct srcu_struct **sspp = mod->srcu_struct_ptrs; > + int ret; > + > + for (i = 0; i < mod->num_srcu_structs; i++) { > + ret = init_srcu_struct(*(sspp++)); > + if (WARN_ON_ONCE(ret)) > + return ret; > + } > + return 0; > +} > + > +/* Clean up any global-scope srcu_struct structures used by this module. */ > +static void srcu_module_going(struct module *mod) > +{ > + int i; > + struct srcu_struct **sspp = mod->srcu_struct_ptrs; > + > + for (i = 0; i < mod->num_srcu_structs; i++) > + cleanup_srcu_struct(*(sspp++)); > +} > + > +/* Handle one module, either coming or going. */ > +static int srcu_module_notify(struct notifier_block *self, > + unsigned long val, void *data) > +{ > + struct module *mod = data; > + int ret = 0; > + > + switch (val) { > + case MODULE_STATE_COMING: > + ret = srcu_module_coming(mod); > + break; > + case MODULE_STATE_GOING: > + srcu_module_going(mod); > + break; > + default: > + break; > + } > + return ret; > +} > + > +static struct notifier_block srcu_module_nb = { > + .notifier_call = srcu_module_notify, > + .priority = 0, > +}; > + > +static __init int init_srcu_module_notifier(void) > +{ > + int ret; > + > + ret = register_module_notifier(&srcu_module_nb); > + if (ret) > + pr_warn("Failed to register srcu module notifier\n"); > + return ret; > +} > +late_initcall(init_srcu_module_notifier); > + > +#endif /* #ifdef CONFIG_MODULES */ >