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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
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@ -58,7 +58,6 @@ void arch_jump_label_transform(struct jump_entry *e,
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insn.word = 0; /* nop */
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}
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get_online_cpus();
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mutex_lock(&text_mutex);
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if (IS_ENABLED(CONFIG_CPU_MICROMIPS)) {
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insn_p->halfword[0] = insn.word >> 16;
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@ -70,7 +69,6 @@ void arch_jump_label_transform(struct jump_entry *e,
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(unsigned long)insn_p + sizeof(*insn_p));
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mutex_unlock(&text_mutex);
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put_online_cpus();
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}
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#endif /* HAVE_JUMP_LABEL */
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@ -41,12 +41,10 @@ void arch_jump_label_transform(struct jump_entry *entry,
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val = 0x01000000;
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}
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get_online_cpus();
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mutex_lock(&text_mutex);
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*insn = val;
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flushi(insn);
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mutex_unlock(&text_mutex);
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put_online_cpus();
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}
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#endif
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@ -45,14 +45,12 @@ static void __jump_label_transform(struct jump_entry *e,
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void arch_jump_label_transform(struct jump_entry *e,
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enum jump_label_type type)
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{
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get_online_cpus();
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mutex_lock(&text_mutex);
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__jump_label_transform(e, type);
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flush_icache_range(e->code, e->code + sizeof(tilegx_bundle_bits));
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mutex_unlock(&text_mutex);
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put_online_cpus();
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}
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__init_or_module void arch_jump_label_transform_static(struct jump_entry *e,
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@ -105,11 +105,9 @@ static void __jump_label_transform(struct jump_entry *entry,
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void arch_jump_label_transform(struct jump_entry *entry,
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enum jump_label_type type)
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{
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get_online_cpus();
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mutex_lock(&text_mutex);
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__jump_label_transform(entry, type, NULL, 0);
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mutex_unlock(&text_mutex);
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put_online_cpus();
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}
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static enum {
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@ -15,6 +15,7 @@
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#include <linux/static_key.h>
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#include <linux/jump_label_ratelimit.h>
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#include <linux/bug.h>
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#include <linux/cpu.h>
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#ifdef HAVE_JUMP_LABEL
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@ -124,6 +125,7 @@ void static_key_slow_inc(struct static_key *key)
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return;
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}
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cpus_read_lock();
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jump_label_lock();
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if (atomic_read(&key->enabled) == 0) {
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atomic_set(&key->enabled, -1);
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@ -133,12 +135,14 @@ void static_key_slow_inc(struct static_key *key)
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atomic_inc(&key->enabled);
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}
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jump_label_unlock();
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cpus_read_unlock();
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}
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EXPORT_SYMBOL_GPL(static_key_slow_inc);
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static void __static_key_slow_dec(struct static_key *key,
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unsigned long rate_limit, struct delayed_work *work)
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{
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cpus_read_lock();
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/*
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* The negative count check is valid even when a negative
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* key->enabled is in use by static_key_slow_inc(); a
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@ -149,6 +153,7 @@ static void __static_key_slow_dec(struct static_key *key,
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if (!atomic_dec_and_mutex_lock(&key->enabled, &jump_label_mutex)) {
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WARN(atomic_read(&key->enabled) < 0,
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"jump label: negative count!\n");
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cpus_read_unlock();
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return;
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}
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@ -159,6 +164,7 @@ static void __static_key_slow_dec(struct static_key *key,
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jump_label_update(key);
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}
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jump_label_unlock();
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cpus_read_unlock();
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}
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static void jump_label_update_timeout(struct work_struct *work)
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@ -334,6 +340,7 @@ void __init jump_label_init(void)
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if (static_key_initialized)
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return;
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cpus_read_lock();
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jump_label_lock();
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jump_label_sort_entries(iter_start, iter_stop);
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@ -353,6 +360,7 @@ void __init jump_label_init(void)
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}
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static_key_initialized = true;
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jump_label_unlock();
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cpus_read_unlock();
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}
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#ifdef CONFIG_MODULES
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@ -590,28 +598,28 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,
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struct module *mod = data;
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int ret = 0;
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cpus_read_lock();
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jump_label_lock();
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switch (val) {
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case MODULE_STATE_COMING:
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jump_label_lock();
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ret = jump_label_add_module(mod);
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if (ret) {
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WARN(1, "Failed to allocatote memory: jump_label may not work properly.\n");
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jump_label_del_module(mod);
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}
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jump_label_unlock();
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break;
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case MODULE_STATE_GOING:
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jump_label_lock();
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jump_label_del_module(mod);
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jump_label_unlock();
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break;
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case MODULE_STATE_LIVE:
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jump_label_lock();
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jump_label_invalidate_module_init(mod);
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jump_label_unlock();
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break;
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}
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jump_label_unlock();
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cpus_read_unlock();
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return notifier_from_errno(ret);
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}
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