[PATCH v2 09/45] smp: Use get/put_online_cpus_atomic() to prevent CPU offline
Srivatsa S. Bhat
srivatsa.bhat at linux.vnet.ibm.com
Wed Jun 26 06:27:02 EST 2013
Once stop_machine() is gone from the CPU offline path, we won't be able
to depend on disabling preemption 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.
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Wang YanQing <udknight at gmail.com>
Cc: Shaohua Li <shli at fusionio.com>
Cc: Jan Beulich <jbeulich at suse.com>
Cc: liguang <lig.fnst at cn.fujitsu.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat at linux.vnet.ibm.com>
---
kernel/smp.c | 52 ++++++++++++++++++++++++++++++----------------------
1 file changed, 30 insertions(+), 22 deletions(-)
diff --git a/kernel/smp.c b/kernel/smp.c
index 4dba0f7..1f36d6d 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -232,7 +232,7 @@ 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();
+ this_cpu = get_online_cpus_atomic();
/*
* Can deadlock when called with interrupts disabled.
@@ -264,7 +264,7 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
}
}
- put_cpu();
+ put_online_cpus_atomic();
return err;
}
@@ -294,7 +294,7 @@ int smp_call_function_any(const struct cpumask *mask,
int ret;
/* Try for same CPU (cheapest) */
- cpu = get_cpu();
+ cpu = get_online_cpus_atomic();
if (cpumask_test_cpu(cpu, mask))
goto call;
@@ -310,7 +310,7 @@ 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);
@@ -331,7 +331,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd,
unsigned int this_cpu;
unsigned long flags;
- this_cpu = get_cpu();
+ this_cpu = 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
@@ -349,7 +350,8 @@ void __smp_call_function_single(int cpu, struct call_single_data *csd,
csd_lock(csd);
generic_exec_single(cpu, csd, wait);
}
- put_cpu();
+
+ put_online_cpus_atomic();
}
/**
@@ -370,7 +372,9 @@ void smp_call_function_many(const struct cpumask *mask,
smp_call_func_t func, void *info, bool wait)
{
struct call_function_data *cfd;
- int cpu, next_cpu, this_cpu = smp_processor_id();
+ int cpu, next_cpu, this_cpu;
+
+ this_cpu = get_online_cpus_atomic();
/*
* Can deadlock when called with interrupts disabled.
@@ -388,7 +392,7 @@ void smp_call_function_many(const struct cpumask *mask,
/* No online cpus? We're done. */
if (cpu >= nr_cpu_ids)
- return;
+ goto out;
/* Do we have another CPU which isn't us? */
next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask);
@@ -398,7 +402,7 @@ void smp_call_function_many(const struct cpumask *mask,
/* Fastpath: do that cpu by itself. */
if (next_cpu >= nr_cpu_ids) {
smp_call_function_single(cpu, func, info, wait);
- return;
+ goto out;
}
cfd = &__get_cpu_var(cfd_data);
@@ -408,7 +412,7 @@ void smp_call_function_many(const struct cpumask *mask,
/* Some callers race with other cpus changing the passed mask */
if (unlikely(!cpumask_weight(cfd->cpumask)))
- return;
+ goto out;
/*
* After we put an entry into the list, cfd->cpumask may be cleared
@@ -443,6 +447,9 @@ void smp_call_function_many(const struct cpumask *mask,
csd_lock_wait(csd);
}
}
+
+out:
+ put_online_cpus_atomic();
}
EXPORT_SYMBOL(smp_call_function_many);
@@ -463,9 +470,9 @@ 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;
}
@@ -565,12 +572,12 @@ int on_each_cpu(void (*func) (void *info), void *info, int wait)
unsigned long flags;
int ret = 0;
- preempt_disable();
+ get_online_cpus_atomic();
ret = smp_call_function(func, info, wait);
local_irq_save(flags);
func(info);
local_irq_restore(flags);
- preempt_enable();
+ put_online_cpus_atomic();
return ret;
}
EXPORT_SYMBOL(on_each_cpu);
@@ -592,7 +599,7 @@ EXPORT_SYMBOL(on_each_cpu);
void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
void *info, bool wait)
{
- int cpu = get_cpu();
+ unsigned int cpu = get_online_cpus_atomic();
smp_call_function_many(mask, func, info, wait);
if (cpumask_test_cpu(cpu, mask)) {
@@ -600,7 +607,7 @@ void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
func(info);
local_irq_enable();
}
- put_cpu();
+ put_online_cpus_atomic();
}
EXPORT_SYMBOL(on_each_cpu_mask);
@@ -625,8 +632,9 @@ EXPORT_SYMBOL(on_each_cpu_mask);
* The function might sleep if the GFP flags indicates a non
* atomic allocation is allowed.
*
- * Preemption is disabled to protect against CPUs going offline but not online.
- * CPUs going online during the call will not be seen or sent an IPI.
+ * We use get/put_online_cpus_atomic() to protect against CPUs going
+ * offline but not online. CPUs going online during the call will
+ * not be seen or sent an IPI.
*
* You must not call this function with disabled interrupts or
* from a hardware interrupt handler or from a bottom half handler.
@@ -641,26 +649,26 @@ void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
might_sleep_if(gfp_flags & __GFP_WAIT);
if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
- preempt_disable();
+ get_online_cpus_atomic();
for_each_online_cpu(cpu)
if (cond_func(cpu, info))
cpumask_set_cpu(cpu, cpus);
on_each_cpu_mask(cpus, func, info, wait);
- preempt_enable();
+ put_online_cpus_atomic();
free_cpumask_var(cpus);
} else {
/*
* No free cpumask, bother. No matter, we'll
* just have to IPI them one by one.
*/
- preempt_disable();
+ get_online_cpus_atomic();
for_each_online_cpu(cpu)
if (cond_func(cpu, info)) {
ret = smp_call_function_single(cpu, func,
info, wait);
WARN_ON_ONCE(!ret);
}
- preempt_enable();
+ put_online_cpus_atomic();
}
}
EXPORT_SYMBOL(on_each_cpu_cond);
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