From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947483Ab3BIAHx (ORCPT ); Fri, 8 Feb 2013 19:07:53 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:34143 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1947339Ab3BIAHs (ORCPT ); Fri, 8 Feb 2013 19:07:48 -0500 Date: Fri, 8 Feb 2013 16:07:17 -0800 From: "Paul E. McKenney" To: "Srivatsa S. Bhat" Cc: tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org, rostedt@goodmis.org, wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com, rjw@sisk.pl, sbw@mit.edu, fweisbec@gmail.com, linux@arm.linux.org.uk, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 09/45] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Message-ID: <20130209000717.GP2666@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13020900-5518-0000-0000-00000B693D0A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 22, 2013 at 01:05:10PM +0530, Srivatsa S. Bhat wrote: > Once stop_machine() is gone from the CPU offline path, we won't be able to > depend on preempt_disable() to prevent CPUs from going offline from under us. > > Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, > while invoking from atomic context. > > Signed-off-by: Srivatsa S. Bhat Would it make sense for get_online_cpus_atomic() to return the current CPU number? Looks good otherwise. Thanx, Paul > --- > > kernel/smp.c | 40 ++++++++++++++++++++++++++-------------- > 1 file changed, 26 insertions(+), 14 deletions(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index 29dd40a..f421bcc 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -310,7 +310,8 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > * prevent preemption and reschedule on another processor, > * as well as CPU removal > */ > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + this_cpu = smp_processor_id(); > > /* > * Can deadlock when called with interrupts disabled. > @@ -342,7 +343,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > } > } > > - put_cpu(); > + put_online_cpus_atomic(); > > return err; > } > @@ -371,8 +372,10 @@ int smp_call_function_any(const struct cpumask *mask, > const struct cpumask *nodemask; > int ret; > > + get_online_cpus_atomic(); > /* Try for same CPU (cheapest) */ > - cpu = get_cpu(); > + cpu = smp_processor_id(); > + > if (cpumask_test_cpu(cpu, mask)) > goto call; > > @@ -388,7 +391,7 @@ int smp_call_function_any(const struct cpumask *mask, > cpu = cpumask_any_and(mask, cpu_online_mask); > call: > ret = smp_call_function_single(cpu, func, info, wait); > - put_cpu(); > + put_online_cpus_atomic(); > return ret; > } > EXPORT_SYMBOL_GPL(smp_call_function_any); > @@ -409,25 +412,28 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, > unsigned int this_cpu; > unsigned long flags; > > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + > + this_cpu = smp_processor_id(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > * send smp call function interrupt to this cpu and as such deadlocks > * can't happen. > */ > - WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() > + WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled() > && !oops_in_progress); > > if (cpu == this_cpu) { > local_irq_save(flags); > data->func(data->info); > local_irq_restore(flags); > - } else { > + } else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { > csd_lock(data); > generic_exec_single(cpu, data, wait); > } > - put_cpu(); > + put_online_cpus_atomic(); > } > > /** > @@ -451,6 +457,8 @@ void smp_call_function_many(const struct cpumask *mask, > unsigned long flags; > int refs, cpu, next_cpu, this_cpu = smp_processor_id(); > > + get_online_cpus_atomic(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > @@ -467,17 +475,18 @@ void smp_call_function_many(const struct cpumask *mask, > > /* No online cpus? We're done. */ > if (cpu >= nr_cpu_ids) > - return; > + goto out_unlock; > > /* Do we have another CPU which isn't us? */ > next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); > if (next_cpu == this_cpu) > - next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); > + next_cpu = cpumask_next_and(next_cpu, mask, > + cpu_online_mask); > > /* Fastpath: do that cpu by itself. */ > if (next_cpu >= nr_cpu_ids) { > smp_call_function_single(cpu, func, info, wait); > - return; > + goto out_unlock; > } > > data = &__get_cpu_var(cfd_data); > @@ -523,7 +532,7 @@ void smp_call_function_many(const struct cpumask *mask, > /* Some callers race with other cpus changing the passed mask */ > if (unlikely(!refs)) { > csd_unlock(&data->csd); > - return; > + goto out_unlock; > } > > raw_spin_lock_irqsave(&call_function.lock, flags); > @@ -554,6 +563,9 @@ void smp_call_function_many(const struct cpumask *mask, > /* Optionally wait for the CPUs to complete */ > if (wait) > csd_lock_wait(&data->csd); > + > +out_unlock: > + put_online_cpus_atomic(); > } > EXPORT_SYMBOL(smp_call_function_many); > > @@ -574,9 +586,9 @@ EXPORT_SYMBOL(smp_call_function_many); > */ > int smp_call_function(smp_call_func_t func, void *info, int wait) > { > - preempt_disable(); > + get_online_cpus_atomic(); > smp_call_function_many(cpu_online_mask, func, info, wait); > - preempt_enable(); > + put_online_cpus_atomic(); > > return 0; > } > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e9.ny.us.ibm.com (e9.ny.us.ibm.com [32.97.182.139]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e9.ny.us.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 47F662C0082 for ; Sat, 9 Feb 2013 11:07:28 +1100 (EST) Received: from /spool/local by e9.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 8 Feb 2013 19:07:25 -0500 Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 922BF6E801A for ; Fri, 8 Feb 2013 19:07:20 -0500 (EST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r1907Len323774 for ; Fri, 8 Feb 2013 19:07:22 -0500 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r1907IJP002139 for ; Fri, 8 Feb 2013 17:07:21 -0700 Date: Fri, 8 Feb 2013 16:07:17 -0800 From: "Paul E. McKenney" To: "Srivatsa S. Bhat" Subject: Re: [PATCH v5 09/45] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Message-ID: <20130209000717.GP2666@linux.vnet.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> Cc: linux-doc@vger.kernel.org, peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, mingo@kernel.org, linux-arch@vger.kernel.org, linux@arm.linux.org.uk, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, rostedt@goodmis.org, rjw@sisk.pl, namhyung@kernel.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, oleg@redhat.com, sbw@mit.edu, tj@kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Reply-To: paulmck@linux.vnet.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jan 22, 2013 at 01:05:10PM +0530, Srivatsa S. Bhat wrote: > Once stop_machine() is gone from the CPU offline path, we won't be able to > depend on preempt_disable() to prevent CPUs from going offline from under us. > > Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, > while invoking from atomic context. > > Signed-off-by: Srivatsa S. Bhat Would it make sense for get_online_cpus_atomic() to return the current CPU number? Looks good otherwise. Thanx, Paul > --- > > kernel/smp.c | 40 ++++++++++++++++++++++++++-------------- > 1 file changed, 26 insertions(+), 14 deletions(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index 29dd40a..f421bcc 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -310,7 +310,8 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > * prevent preemption and reschedule on another processor, > * as well as CPU removal > */ > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + this_cpu = smp_processor_id(); > > /* > * Can deadlock when called with interrupts disabled. > @@ -342,7 +343,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > } > } > > - put_cpu(); > + put_online_cpus_atomic(); > > return err; > } > @@ -371,8 +372,10 @@ int smp_call_function_any(const struct cpumask *mask, > const struct cpumask *nodemask; > int ret; > > + get_online_cpus_atomic(); > /* Try for same CPU (cheapest) */ > - cpu = get_cpu(); > + cpu = smp_processor_id(); > + > if (cpumask_test_cpu(cpu, mask)) > goto call; > > @@ -388,7 +391,7 @@ int smp_call_function_any(const struct cpumask *mask, > cpu = cpumask_any_and(mask, cpu_online_mask); > call: > ret = smp_call_function_single(cpu, func, info, wait); > - put_cpu(); > + put_online_cpus_atomic(); > return ret; > } > EXPORT_SYMBOL_GPL(smp_call_function_any); > @@ -409,25 +412,28 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, > unsigned int this_cpu; > unsigned long flags; > > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + > + this_cpu = smp_processor_id(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > * send smp call function interrupt to this cpu and as such deadlocks > * can't happen. > */ > - WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() > + WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled() > && !oops_in_progress); > > if (cpu == this_cpu) { > local_irq_save(flags); > data->func(data->info); > local_irq_restore(flags); > - } else { > + } else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { > csd_lock(data); > generic_exec_single(cpu, data, wait); > } > - put_cpu(); > + put_online_cpus_atomic(); > } > > /** > @@ -451,6 +457,8 @@ void smp_call_function_many(const struct cpumask *mask, > unsigned long flags; > int refs, cpu, next_cpu, this_cpu = smp_processor_id(); > > + get_online_cpus_atomic(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > @@ -467,17 +475,18 @@ void smp_call_function_many(const struct cpumask *mask, > > /* No online cpus? We're done. */ > if (cpu >= nr_cpu_ids) > - return; > + goto out_unlock; > > /* Do we have another CPU which isn't us? */ > next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); > if (next_cpu == this_cpu) > - next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); > + next_cpu = cpumask_next_and(next_cpu, mask, > + cpu_online_mask); > > /* Fastpath: do that cpu by itself. */ > if (next_cpu >= nr_cpu_ids) { > smp_call_function_single(cpu, func, info, wait); > - return; > + goto out_unlock; > } > > data = &__get_cpu_var(cfd_data); > @@ -523,7 +532,7 @@ void smp_call_function_many(const struct cpumask *mask, > /* Some callers race with other cpus changing the passed mask */ > if (unlikely(!refs)) { > csd_unlock(&data->csd); > - return; > + goto out_unlock; > } > > raw_spin_lock_irqsave(&call_function.lock, flags); > @@ -554,6 +563,9 @@ void smp_call_function_many(const struct cpumask *mask, > /* Optionally wait for the CPUs to complete */ > if (wait) > csd_lock_wait(&data->csd); > + > +out_unlock: > + put_online_cpus_atomic(); > } > EXPORT_SYMBOL(smp_call_function_many); > > @@ -574,9 +586,9 @@ EXPORT_SYMBOL(smp_call_function_many); > */ > int smp_call_function(smp_call_func_t func, void *info, int wait) > { > - preempt_disable(); > + get_online_cpus_atomic(); > smp_call_function_many(cpu_online_mask, func, info, wait); > - preempt_enable(); > + put_online_cpus_atomic(); > > return 0; > } > From mboxrd@z Thu Jan 1 00:00:00 1970 From: paulmck@linux.vnet.ibm.com (Paul E. McKenney) Date: Fri, 8 Feb 2013 16:07:17 -0800 Subject: [PATCH v5 09/45] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly In-Reply-To: <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> Message-ID: <20130209000717.GP2666@linux.vnet.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 22, 2013 at 01:05:10PM +0530, Srivatsa S. Bhat wrote: > Once stop_machine() is gone from the CPU offline path, we won't be able to > depend on preempt_disable() to prevent CPUs from going offline from under us. > > Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, > while invoking from atomic context. > > Signed-off-by: Srivatsa S. Bhat Would it make sense for get_online_cpus_atomic() to return the current CPU number? Looks good otherwise. Thanx, Paul > --- > > kernel/smp.c | 40 ++++++++++++++++++++++++++-------------- > 1 file changed, 26 insertions(+), 14 deletions(-) > > diff --git a/kernel/smp.c b/kernel/smp.c > index 29dd40a..f421bcc 100644 > --- a/kernel/smp.c > +++ b/kernel/smp.c > @@ -310,7 +310,8 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > * prevent preemption and reschedule on another processor, > * as well as CPU removal > */ > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + this_cpu = smp_processor_id(); > > /* > * Can deadlock when called with interrupts disabled. > @@ -342,7 +343,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info, > } > } > > - put_cpu(); > + put_online_cpus_atomic(); > > return err; > } > @@ -371,8 +372,10 @@ int smp_call_function_any(const struct cpumask *mask, > const struct cpumask *nodemask; > int ret; > > + get_online_cpus_atomic(); > /* Try for same CPU (cheapest) */ > - cpu = get_cpu(); > + cpu = smp_processor_id(); > + > if (cpumask_test_cpu(cpu, mask)) > goto call; > > @@ -388,7 +391,7 @@ int smp_call_function_any(const struct cpumask *mask, > cpu = cpumask_any_and(mask, cpu_online_mask); > call: > ret = smp_call_function_single(cpu, func, info, wait); > - put_cpu(); > + put_online_cpus_atomic(); > return ret; > } > EXPORT_SYMBOL_GPL(smp_call_function_any); > @@ -409,25 +412,28 @@ void __smp_call_function_single(int cpu, struct call_single_data *data, > unsigned int this_cpu; > unsigned long flags; > > - this_cpu = get_cpu(); > + get_online_cpus_atomic(); > + > + this_cpu = smp_processor_id(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > * send smp call function interrupt to this cpu and as such deadlocks > * can't happen. > */ > - WARN_ON_ONCE(cpu_online(smp_processor_id()) && wait && irqs_disabled() > + WARN_ON_ONCE(cpu_online(this_cpu) && wait && irqs_disabled() > && !oops_in_progress); > > if (cpu == this_cpu) { > local_irq_save(flags); > data->func(data->info); > local_irq_restore(flags); > - } else { > + } else if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) { > csd_lock(data); > generic_exec_single(cpu, data, wait); > } > - put_cpu(); > + put_online_cpus_atomic(); > } > > /** > @@ -451,6 +457,8 @@ void smp_call_function_many(const struct cpumask *mask, > unsigned long flags; > int refs, cpu, next_cpu, this_cpu = smp_processor_id(); > > + get_online_cpus_atomic(); > + > /* > * Can deadlock when called with interrupts disabled. > * We allow cpu's that are not yet online though, as no one else can > @@ -467,17 +475,18 @@ void smp_call_function_many(const struct cpumask *mask, > > /* No online cpus? We're done. */ > if (cpu >= nr_cpu_ids) > - return; > + goto out_unlock; > > /* Do we have another CPU which isn't us? */ > next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); > if (next_cpu == this_cpu) > - next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); > + next_cpu = cpumask_next_and(next_cpu, mask, > + cpu_online_mask); > > /* Fastpath: do that cpu by itself. */ > if (next_cpu >= nr_cpu_ids) { > smp_call_function_single(cpu, func, info, wait); > - return; > + goto out_unlock; > } > > data = &__get_cpu_var(cfd_data); > @@ -523,7 +532,7 @@ void smp_call_function_many(const struct cpumask *mask, > /* Some callers race with other cpus changing the passed mask */ > if (unlikely(!refs)) { > csd_unlock(&data->csd); > - return; > + goto out_unlock; > } > > raw_spin_lock_irqsave(&call_function.lock, flags); > @@ -554,6 +563,9 @@ void smp_call_function_many(const struct cpumask *mask, > /* Optionally wait for the CPUs to complete */ > if (wait) > csd_lock_wait(&data->csd); > + > +out_unlock: > + put_online_cpus_atomic(); > } > EXPORT_SYMBOL(smp_call_function_many); > > @@ -574,9 +586,9 @@ EXPORT_SYMBOL(smp_call_function_many); > */ > int smp_call_function(smp_call_func_t func, void *info, int wait) > { > - preempt_disable(); > + get_online_cpus_atomic(); > smp_call_function_many(cpu_online_mask, func, info, wait); > - preempt_enable(); > + put_online_cpus_atomic(); > > return 0; > } >