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Message-ID: <20121207173842.27305.52029.stgit@srivatsabhat.in.ibm.com>
Date: Fri, 07 Dec 2012 23:08:44 +0530
From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To: tglx@...utronix.de, peterz@...radead.org,
paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org,
vincent.guittot@...aro.org, tj@...nel.org, oleg@...hat.com
Cc: sbw@....edu, amit.kucheria@...aro.org, rostedt@...dmis.org,
rjw@...k.pl, srivatsa.bhat@...ux.vnet.ibm.com,
wangyun@...ux.vnet.ibm.com, xiaoguangrong@...ux.vnet.ibm.com,
nikunj@...ux.vnet.ibm.com, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v3 3/9] smp,
cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly
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 <srivatsa.bhat@...ux.vnet.ibm.com>
---
kernel/smp.c | 38 +++++++++++++++++++++++++-------------
1 file changed, 25 insertions(+), 13 deletions(-)
diff --git a/kernel/smp.c b/kernel/smp.c
index 29dd40a..ce1a866 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);
@@ -409,14 +412,17 @@ 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) {
@@ -427,7 +433,7 @@ void __smp_call_function_single(int cpu, struct call_single_data *data,
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;
}
--
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