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Message-Id: <1308071218-5912-2-git-send-email-tj@kernel.org>
Date: Tue, 14 Jun 2011 19:06:56 +0200
From: Tejun Heo <tj@...nel.org>
To: x86@...nel.org, mingo@...e.hu, akpm@...ux-foundation.org,
torvalds@...ux-foundation.org, suresh.b.siddha@...el.com,
a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>
Subject: [PATCH 1/3] stop_machine: kill __stop_machine()
stop_machine() is different from __stop_machine() in that it
automatically calls get/put_online_cpus() to disable CPU hotplug. For
__stop_machine(), the caller is responsible for achieving exclusion
against CPU hotplug using either get/put_online_cpus() or
cpu_hotplug_begin/done().
However, get_online_cpus() can nest safely inside both another
get_online_cpus() or cpu_hotplug_begin(); thus, it's safe to use
stop_machine() instead of __stop_machine() making the distinction
pointless - the overhead of extra get/put_online_cpus() is negligible
compared to stop_machine and they basically become noop if hotplug is
in progress.
This patch converts all current __stop_machine() users to
stop_machine() and kills __stop_machine(). While at it, move function
comment for stop_machine() from function declaration to definition and
update it slightly.
Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: x86@...nel.org
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Suresh Siddha <suresh.b.siddha@...el.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
arch/x86/kernel/alternative.c | 5 ++---
include/linux/stop_machine.h | 34 ++--------------------------------
kernel/cpu.c | 2 +-
kernel/stop_machine.c | 38 +++++++++++++++++++++++++++-----------
4 files changed, 32 insertions(+), 47 deletions(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a81f2d5..f7a021e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -719,8 +719,7 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
tpp.nparams = 1;
atomic_set(&stop_machine_first, 1);
wrote_text = 0;
- /* Use __stop_machine() because the caller already got online_cpus. */
- __stop_machine(stop_machine_text_poke, (void *)&tpp, cpu_online_mask);
+ stop_machine(stop_machine_text_poke, (void *)&tpp, cpu_online_mask);
return addr;
}
@@ -741,5 +740,5 @@ void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n)
atomic_set(&stop_machine_first, 1);
wrote_text = 0;
- __stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
+ stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
}
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 092dc9b..4f1a73c 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -98,36 +98,12 @@ static inline int try_stop_cpus(const struct cpumask *cpumask,
*/
#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
-/**
- * stop_machine: freeze the machine on all CPUs and run this function
- * @fn: the function to run
- * @data: the data ptr for the @fn()
- * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
- *
- * Description: This causes a thread to be scheduled on every cpu,
- * each of which disables interrupts. The result is that no one is
- * holding a spinlock or inside any other preempt-disabled region when
- * @fn() runs.
- *
- * This can be thought of as a very heavy write lock, equivalent to
- * grabbing every spinlock in the kernel. */
int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
-/**
- * __stop_machine: freeze the machine on all CPUs and run this function
- * @fn: the function to run
- * @data: the data ptr for the @fn
- * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
- *
- * Description: This is a special version of the above, which assumes cpus
- * won't come or go while it's being called. Used by hotplug cpu.
- */
-int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
-
#else /* CONFIG_STOP_MACHINE && CONFIG_SMP */
-static inline int __stop_machine(int (*fn)(void *), void *data,
- const struct cpumask *cpus)
+static inline int stop_machine(int (*fn)(void *), void *data,
+ const struct cpumask *cpus)
{
int ret;
local_irq_disable();
@@ -136,11 +112,5 @@ static inline int __stop_machine(int (*fn)(void *), void *data,
return ret;
}
-static inline int stop_machine(int (*fn)(void *), void *data,
- const struct cpumask *cpus)
-{
- return __stop_machine(fn, data, cpus);
-}
-
#endif /* CONFIG_STOP_MACHINE && CONFIG_SMP */
#endif /* _LINUX_STOP_MACHINE */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 12b7458..bb23d5b 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -235,7 +235,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
goto out_release;
}
- err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
+ err = stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
if (err) {
/* CPU didn't die: tell everyone. Can't complain. */
cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index e3516b2..3d3f47d 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -464,24 +464,40 @@ static int stop_machine_cpu_stop(void *data)
return err;
}
-int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
+/**
+ * stop_machine - freeze the machine on all online CPUs and run this function
+ * @fn: the function to run
+ * @data: the data ptr for the @fn()
+ * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
+ *
+ * This causes a thread to be scheduled on every cpu, each of which
+ * disables interrupts. The result is that no one is holding a spinlock or
+ * inside any other preempt-disabled region when @fn() runs.
+ *
+ * This can be thought of as a very heavy write lock, equivalent to
+ * grabbing every spinlock in the kernel.
+ *
+ * CONTEXT:
+ * Might sleep. Temporarily stops all online CPUs.
+ *
+ * RETURNS:
+ * 0 if all executions of @fn returned 0, any non zero return value if any
+ * returned non zero.
+ */
+int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
{
struct stop_machine_data smdata = { .fn = fn, .data = data,
- .num_threads = num_online_cpus(),
.active_cpus = cpus };
-
- /* Set the initial state and stop all online cpus. */
- set_state(&smdata, STOPMACHINE_PREPARE);
- return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata);
-}
-
-int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
-{
int ret;
/* No CPUs can come up or down during this. */
get_online_cpus();
- ret = __stop_machine(fn, data, cpus);
+ smdata.num_threads = num_online_cpus(),
+
+ /* Set the initial state and stop all online cpus. */
+ set_state(&smdata, STOPMACHINE_PREPARE);
+ ret = stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata);
+
put_online_cpus();
return ret;
}
--
1.7.5.2
--
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