lkml.org 
[lkml]   [2017]   [Apr]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:smp/hotplug] jump_label: Pull get_online_cpus() into generic code
Commit-ID:  82947f31231157d8ab70fa8961f23fd3887a3327
Gitweb: http://git.kernel.org/tip/82947f31231157d8ab70fa8961f23fd3887a3327
Author: Peter Zijlstra (Intel) <peterz@infradead.org>
AuthorDate: Tue, 18 Apr 2017 19:05:03 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 20 Apr 2017 13:08:57 +0200

jump_label: Pull get_online_cpus() into generic code

This change does two things:

- it moves the get_online_cpus() call into generic code, with the aim of
later providing some static_key ops that avoid it.

- as a side effect it inverts the lock order between cpu_hotplug_lock and
jump_label_mutex.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: jbaron@akamai.com
Link: http://lkml.kernel.org/r/20170418103422.590118425@infradead.org

---
arch/mips/kernel/jump_label.c | 2 --
arch/sparc/kernel/jump_label.c | 2 --
arch/tile/kernel/jump_label.c | 2 --
arch/x86/kernel/jump_label.c | 2 --
kernel/jump_label.c | 14 ++++++++++++++
5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/mips/kernel/jump_label.c b/arch/mips/kernel/jump_label.c
index 3e586da..32e3168 100644
--- a/arch/mips/kernel/jump_label.c
+++ b/arch/mips/kernel/jump_label.c
@@ -58,7 +58,6 @@ void arch_jump_label_transform(struct jump_entry *e,
insn.word = 0; /* nop */
}

- get_online_cpus();
mutex_lock(&text_mutex);
if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
insn_p->halfword[0] = insn.word >> 16;
@@ -70,7 +69,6 @@ void arch_jump_label_transform(struct jump_entry *e,
(unsigned long)insn_p + sizeof(*insn_p));

mutex_unlock(&text_mutex);
- put_online_cpus();
}

#endif /* HAVE_JUMP_LABEL */
diff --git a/arch/sparc/kernel/jump_label.c b/arch/sparc/kernel/jump_label.c
index 07933b9..93adde1 100644
--- a/arch/sparc/kernel/jump_label.c
+++ b/arch/sparc/kernel/jump_label.c
@@ -41,12 +41,10 @@ void arch_jump_label_transform(struct jump_entry *entry,
val = 0x01000000;
}

- get_online_cpus();
mutex_lock(&text_mutex);
*insn = val;
flushi(insn);
mutex_unlock(&text_mutex);
- put_online_cpus();
}

#endif
diff --git a/arch/tile/kernel/jump_label.c b/arch/tile/kernel/jump_label.c
index 07802d5..93931a4 100644
--- a/arch/tile/kernel/jump_label.c
+++ b/arch/tile/kernel/jump_label.c
@@ -45,14 +45,12 @@ static void __jump_label_transform(struct jump_entry *e,
void arch_jump_label_transform(struct jump_entry *e,
enum jump_label_type type)
{
- get_online_cpus();
mutex_lock(&text_mutex);

__jump_label_transform(e, type);
flush_icache_range(e->code, e->code + sizeof(tilegx_bundle_bits));

mutex_unlock(&text_mutex);
- put_online_cpus();
}

__init_or_module void arch_jump_label_transform_static(struct jump_entry *e,
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index c37bd0f..ab4f491 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -105,11 +105,9 @@ static void __jump_label_transform(struct jump_entry *entry,
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
- get_online_cpus();
mutex_lock(&text_mutex);
__jump_label_transform(entry, type, NULL, 0);
mutex_unlock(&text_mutex);
- put_online_cpus();
}

static enum {
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 6c9cb20..f3afe07 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -15,6 +15,7 @@
#include <linux/static_key.h>
#include <linux/jump_label_ratelimit.h>
#include <linux/bug.h>
+#include <linux/cpu.h>

#ifdef HAVE_JUMP_LABEL

@@ -124,6 +125,12 @@ void static_key_slow_inc(struct static_key *key)
return;
}

+ /*
+ * A number of architectures need to synchronize I$ across
+ * the all CPUs, for that to be serialized against CPU hot-plug
+ * we need to avoid CPUs coming online.
+ */
+ get_online_cpus();
jump_label_lock();
if (atomic_read(&key->enabled) == 0) {
atomic_set(&key->enabled, -1);
@@ -133,6 +140,7 @@ void static_key_slow_inc(struct static_key *key)
atomic_inc(&key->enabled);
}
jump_label_unlock();
+ put_online_cpus();
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);

@@ -146,6 +154,7 @@ static void __static_key_slow_dec(struct static_key *key,
* returns is unbalanced, because all other static_key_slow_inc()
* instances block while the update is in progress.
*/
+ get_online_cpus();
if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
WARN(atomic_read(&key->enabled) < 0,
"jump label: negative count!\n");
@@ -159,6 +168,7 @@ static void __static_key_slow_dec(struct static_key *key,
jump_label_update(key);
}
jump_label_unlock();
+ put_online_cpus();
}

static void jump_label_update_timeout(struct work_struct *work)
@@ -592,6 +602,10 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,

switch (val) {
case MODULE_STATE_COMING:
+ /*
+ * XXX do we need get_online_cpus() ? the module isn't
+ * executable yet, so nothing should be looking at our code.
+ */
jump_label_lock();
ret = jump_label_add_module(mod);
if (ret) {
\
 
 \ /
  Last update: 2017-04-20 13:32    [W:0.094 / U:8.204 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site