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Bhat" Subject: [PATCH v5 09/45] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly To: tglx@linutronix.de, peterz@infradead.org, tj@kernel.org, oleg@redhat.com, paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au, mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org Date: Tue, 22 Jan 2013 13:05:10 +0530 Message-ID: <20130122073508.13822.12784.stgit@srivatsabhat.in.ibm.com> In-Reply-To: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012207-2674-0000-0000-0000078F5FEC X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130122_023702_429008_05AD45D0 X-CRM114-Status: GOOD ( 17.33 ) X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-1.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [122.248.162.9 listed in list.dnswl.org] 3.0 KHOP_BIG_TO_CC Sent to 10+ recipients instaed of Bcc or a list -0.7 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: linux-arch@vger.kernel.org, linux@arm.linux.org.uk, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, fweisbec@gmail.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, xiaoguangrong@linux.vnet.ibm.com, rjw@sisk.pl, sbw@mit.edu, wangyun@linux.vnet.ibm.com, srivatsa.bhat@linux.vnet.ibm.com, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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 --- 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; }