lkml.org 
[lkml]   [2013]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v6 10/46] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly
Date
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@linux.vnet.ibm.com>
---

kernel/smp.c | 40 ++++++++++++++++++++++++++--------------
1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 69f38bd..0f40d36 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -315,7 +315,8 @@ 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.
@@ -347,7 +348,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
}
}

- put_cpu();
+ put_online_cpus_atomic();

return err;
}
@@ -376,8 +377,10 @@ 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;

@@ -393,7 +396,7 @@ 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);
@@ -414,25 +417,28 @@ 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();
}

/**
@@ -456,6 +462,8 @@ 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
@@ -472,17 +480,18 @@ 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);
@@ -528,7 +537,7 @@ 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;
}

/*
@@ -565,6 +574,9 @@ 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);

@@ -585,9 +597,9 @@ 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;
}


\
 
 \ /
  Last update: 2013-02-18 14:42    [W:0.338 / U:0.196 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site