Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull SMP hotplug updates from Thomas Gleixner:
 "This update is primarily a cleanup of the CPU hotplug locking code.

  The hotplug locking mechanism is an open coded RWSEM, which allows
  recursive locking. The main problem with that is the recursive nature
  as it evades the full lockdep coverage and hides potential deadlocks.

  The rework replaces the open coded RWSEM with a percpu RWSEM and
  establishes full lockdep coverage that way.

  The bulk of the changes fix up recursive locking issues and address
  the now fully reported potential deadlocks all over the place. Some of
  these deadlocks have been observed in the RT tree, but on mainline the
  probability was low enough to hide them away."

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  cpu/hotplug: Constify attribute_group structures
  powerpc: Only obtain cpu_hotplug_lock if called by rtasd
  ARM/hw_breakpoint: Fix possible recursive locking for arch_hw_breakpoint_init
  cpu/hotplug: Remove unused check_for_tasks() function
  perf/core: Don't release cred_guard_mutex if not taken
  cpuhotplug: Link lock stacks for hotplug callbacks
  acpi/processor: Prevent cpu hotplug deadlock
  sched: Provide is_percpu_thread() helper
  cpu/hotplug: Convert hotplug locking to percpu rwsem
  s390: Prevent hotplug rwsem recursion
  arm: Prevent hotplug rwsem recursion
  arm64: Prevent cpu hotplug rwsem recursion
  kprobes: Cure hotplug lock ordering issues
  jump_label: Reorder hotplug lock and jump_label_lock
  perf/tracing/cpuhotplug: Fix locking order
  ACPI/processor: Use cpu_hotplug_disable() instead of get_online_cpus()
  PCI: Replace the racy recursion prevention
  PCI: Use cpu_hotplug_disable() instead of get_online_cpus()
  perf/x86/intel: Drop get_online_cpus() in intel_snb_check_microcode()
  x86/perf: Drop EXPORT of perf_check_microcode
  ...

1 files changed, 32 insertions, 27 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index adfe3b4..6756d75 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -483,11 +483,6 @@ static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
  */
 static void do_optimize_kprobes(void)
 {
-	/* Optimization never be done when disarmed */
-	if (kprobes_all_disarmed || !kprobes_allow_optimization ||
-	    list_empty(&optimizing_list))
-		return;
-
 	/*
 	 * The optimization/unoptimization refers online_cpus via
 	 * stop_machine() and cpu-hotplug modifies online_cpus.
@@ -495,14 +490,19 @@ static void do_optimize_kprobes(void)
 	 * This combination can cause a deadlock (cpu-hotplug try to lock
 	 * text_mutex but stop_machine can not be done because online_cpus
 	 * has been changed)
-	 * To avoid this deadlock, we need to call get_online_cpus()
+	 * To avoid this deadlock, caller must have locked cpu hotplug
 	 * for preventing cpu-hotplug outside of text_mutex locking.
 	 */
-	get_online_cpus();
+	lockdep_assert_cpus_held();
+
+	/* Optimization never be done when disarmed */
+	if (kprobes_all_disarmed || !kprobes_allow_optimization ||
+	    list_empty(&optimizing_list))
+		return;
+
 	mutex_lock(&text_mutex);
 	arch_optimize_kprobes(&optimizing_list);
 	mutex_unlock(&text_mutex);
-	put_online_cpus();
 }
 
 /*
@@ -513,12 +513,13 @@ static void do_unoptimize_kprobes(void)
 {
 	struct optimized_kprobe *op, *tmp;
 
+	/* See comment in do_optimize_kprobes() */
+	lockdep_assert_cpus_held();
+
 	/* Unoptimization must be done anytime */
 	if (list_empty(&unoptimizing_list))
 		return;
 
-	/* Ditto to do_optimize_kprobes */
-	get_online_cpus();
 	mutex_lock(&text_mutex);
 	arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
 	/* Loop free_list for disarming */
@@ -537,7 +538,6 @@ static void do_unoptimize_kprobes(void)
 			list_del_init(&op->list);
 	}
 	mutex_unlock(&text_mutex);
-	put_online_cpus();
 }
 
 /* Reclaim all kprobes on the free_list */
@@ -562,6 +562,7 @@ static void kick_kprobe_optimizer(void)
 static void kprobe_optimizer(struct work_struct *work)
 {
 	mutex_lock(&kprobe_mutex);
+	cpus_read_lock();
 	/* Lock modules while optimizing kprobes */
 	mutex_lock(&module_mutex);
 
@@ -587,6 +588,7 @@ static void kprobe_optimizer(struct work_struct *work)
 	do_free_cleaned_kprobes();
 
 	mutex_unlock(&module_mutex);
+	cpus_read_unlock();
 	mutex_unlock(&kprobe_mutex);
 
 	/* Step 5: Kick optimizer again if needed */
@@ -650,9 +652,8 @@ static void optimize_kprobe(struct kprobe *p)
 /* Short cut to direct unoptimizing */
 static void force_unoptimize_kprobe(struct optimized_kprobe *op)
 {
-	get_online_cpus();
+	lockdep_assert_cpus_held();
 	arch_unoptimize_kprobe(op);
-	put_online_cpus();
 	if (kprobe_disabled(&op->kp))
 		arch_disarm_kprobe(&op->kp);
 }
@@ -791,6 +792,7 @@ static void try_to_optimize_kprobe(struct kprobe *p)
 		return;
 
 	/* For preparing optimization, jump_label_text_reserved() is called */
+	cpus_read_lock();
 	jump_label_lock();
 	mutex_lock(&text_mutex);
 
@@ -812,6 +814,7 @@ static void try_to_optimize_kprobe(struct kprobe *p)
 out:
 	mutex_unlock(&text_mutex);
 	jump_label_unlock();
+	cpus_read_unlock();
 }
 
 #ifdef CONFIG_SYSCTL
@@ -826,6 +829,7 @@ static void optimize_all_kprobes(void)
 	if (kprobes_allow_optimization)
 		goto out;
 
+	cpus_read_lock();
 	kprobes_allow_optimization = true;
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
@@ -833,6 +837,7 @@ static void optimize_all_kprobes(void)
 			if (!kprobe_disabled(p))
 				optimize_kprobe(p);
 	}
+	cpus_read_unlock();
 	printk(KERN_INFO "Kprobes globally optimized\n");
 out:
 	mutex_unlock(&kprobe_mutex);
@@ -851,6 +856,7 @@ static void unoptimize_all_kprobes(void)
 		return;
 	}
 
+	cpus_read_lock();
 	kprobes_allow_optimization = false;
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
@@ -859,6 +865,7 @@ static void unoptimize_all_kprobes(void)
 				unoptimize_kprobe(p, false);
 		}
 	}
+	cpus_read_unlock();
 	mutex_unlock(&kprobe_mutex);
 
 	/* Wait for unoptimizing completion */
@@ -1010,14 +1017,11 @@ static void arm_kprobe(struct kprobe *kp)
 		arm_kprobe_ftrace(kp);
 		return;
 	}
-	/*
-	 * Here, since __arm_kprobe() doesn't use stop_machine(),
-	 * this doesn't cause deadlock on text_mutex. So, we don't
-	 * need get_online_cpus().
-	 */
+	cpus_read_lock();
 	mutex_lock(&text_mutex);
 	__arm_kprobe(kp);
 	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
 }
 
 /* Disarm a kprobe with text_mutex */
@@ -1027,10 +1031,12 @@ static void disarm_kprobe(struct kprobe *kp, bool reopt)
 		disarm_kprobe_ftrace(kp);
 		return;
 	}
-	/* Ditto */
+
+	cpus_read_lock();
 	mutex_lock(&text_mutex);
 	__disarm_kprobe(kp, reopt);
 	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
 }
 
 /*
@@ -1298,13 +1304,10 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
 	int ret = 0;
 	struct kprobe *ap = orig_p;
 
+	cpus_read_lock();
+
 	/* For preparing optimization, jump_label_text_reserved() is called */
 	jump_label_lock();
-	/*
-	 * Get online CPUs to avoid text_mutex deadlock.with stop machine,
-	 * which is invoked by unoptimize_kprobe() in add_new_kprobe()
-	 */
-	get_online_cpus();
 	mutex_lock(&text_mutex);
 
 	if (!kprobe_aggrprobe(orig_p)) {
@@ -1352,8 +1355,8 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
 
 out:
 	mutex_unlock(&text_mutex);
-	put_online_cpus();
 	jump_label_unlock();
+	cpus_read_unlock();
 
 	if (ret == 0 && kprobe_disabled(ap) && !kprobe_disabled(p)) {
 		ap->flags &= ~KPROBE_FLAG_DISABLED;
@@ -1555,9 +1558,12 @@ int register_kprobe(struct kprobe *p)
 		goto out;
 	}
 
-	mutex_lock(&text_mutex);	/* Avoiding text modification */
+	cpus_read_lock();
+	/* Prevent text modification */
+	mutex_lock(&text_mutex);
 	ret = prepare_kprobe(p);
 	mutex_unlock(&text_mutex);
+	cpus_read_unlock();
 	if (ret)
 		goto out;
 
@@ -1570,7 +1576,6 @@ int register_kprobe(struct kprobe *p)
 
 	/* Try to optimize kprobe */
 	try_to_optimize_kprobe(p);
-
 out:
 	mutex_unlock(&kprobe_mutex);