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authorThomas Gleixner <tglx@linutronix.de>2017-05-24 10:15:35 +0200
committerThomas Gleixner <tglx@linutronix.de>2017-05-26 10:10:45 +0200
commitf2545b2d4ce13e068897ef60ae64dffe215f4152 (patch)
tree8f8808b01165daf8e5450f0d5a7fe25f322fb5a6 /kernel
parenta63fbed776c7124ce9f606234267c3c095b2680e (diff)
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jump_label: Reorder hotplug lock and jump_label_lock
The conversion of the hotplug locking to a percpu rwsem unearthed lock ordering issues all over the place. The jump_label code has two issues: 1) Nested get_online_cpus() invocations 2) Ordering problems vs. the cpus rwsem and the jump_label_mutex To cure these, the following lock order has been established; cpus_rwsem -> jump_label_lock -> text_mutex Even if not all architectures need protection against CPU hotplug, taking cpus_rwsem before jump_label_lock is now mandatory in code pathes which actually modify code and therefor need text_mutex protection. Move the get_online_cpus() invocations into the core jump label code and establish the proper lock order where required. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: "David S. Miller" <davem@davemloft.net> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Jason Baron <jbaron@akamai.com> Cc: Ralf Baechle <ralf@linux-mips.org> Link: http://lkml.kernel.org/r/20170524081549.025830817@linutronix.de
Diffstat (limited to 'kernel')
-rw-r--r--kernel/jump_label.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 6c9cb208ac48..d11c506a6ac3 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 +125,7 @@ void static_key_slow_inc(struct static_key *key)
return;
}
+ cpus_read_lock();
jump_label_lock();
if (atomic_read(&key->enabled) == 0) {
atomic_set(&key->enabled, -1);
@@ -133,12 +135,14 @@ void static_key_slow_inc(struct static_key *key)
atomic_inc(&key->enabled);
}
jump_label_unlock();
+ cpus_read_unlock();
}
EXPORT_SYMBOL_GPL(static_key_slow_inc);
static void __static_key_slow_dec(struct static_key *key,
unsigned long rate_limit, struct delayed_work *work)
{
+ cpus_read_lock();
/*
* The negative count check is valid even when a negative
* key->enabled is in use by static_key_slow_inc(); a
@@ -149,6 +153,7 @@ static void __static_key_slow_dec(struct static_key *key,
if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
WARN(atomic_read(&key->enabled) < 0,
"jump label: negative count!\n");
+ cpus_read_unlock();
return;
}
@@ -159,6 +164,7 @@ static void __static_key_slow_dec(struct static_key *key,
jump_label_update(key);
}
jump_label_unlock();
+ cpus_read_unlock();
}
static void jump_label_update_timeout(struct work_struct *work)
@@ -334,6 +340,7 @@ void __init jump_label_init(void)
if (static_key_initialized)
return;
+ cpus_read_lock();
jump_label_lock();
jump_label_sort_entries(iter_start, iter_stop);
@@ -353,6 +360,7 @@ void __init jump_label_init(void)
}
static_key_initialized = true;
jump_label_unlock();
+ cpus_read_unlock();
}
#ifdef CONFIG_MODULES
@@ -590,28 +598,28 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,
struct module *mod = data;
int ret = 0;
+ cpus_read_lock();
+ jump_label_lock();
+
switch (val) {
case MODULE_STATE_COMING:
- jump_label_lock();
ret = jump_label_add_module(mod);
if (ret) {
WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
jump_label_del_module(mod);
}
- jump_label_unlock();
break;
case MODULE_STATE_GOING:
- jump_label_lock();
jump_label_del_module(mod);
- jump_label_unlock();
break;
case MODULE_STATE_LIVE:
- jump_label_lock();
jump_label_invalidate_module_init(mod);
- jump_label_unlock();
break;
}
+ jump_label_unlock();
+ cpus_read_unlock();
+
return notifier_from_errno(ret);
}