Commit-ID: 7f68b6000ddf57c0cdbe94ddfc099ed12820f16a
Gitweb: http://git.kernel.org/tip/7f68b6000ddf57c0cdbe94ddfc099ed12820f16a
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Sun, 23 Apr 2017 12:33:08 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Sun, 23 Apr 2017 19:11:28 +0200
kprobes: Cure hotplug lock ordering issues
The get_online_cpus() rework unearthed lock ordering issues.
Reorder hotpluglock and kprobes_mutex() to avoid circular locking
dependencies.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/kprobes.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 699c5bc..e70a197 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -498,14 +498,13 @@ 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_hotplug_held();
mutex_lock(&text_mutex);
arch_optimize_kprobes(&optimizing_list);
mutex_unlock(&text_mutex);
- put_online_cpus();
}
/*
@@ -521,7 +520,7 @@ static void do_unoptimize_kprobes(void)
return;
/* Ditto to do_optimize_kprobes */
- get_online_cpus();
+ lockdep_assert_hotplug_held();
mutex_lock(&text_mutex);
arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);
/* Loop free_list for disarming */
@@ -540,7 +539,6 @@ 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 */
@@ -564,6 +562,7 @@ static void kick_kprobe_optimizer(void)
/* Kprobe jump optimizer */
static void kprobe_optimizer(struct work_struct *work)
{
+ get_online_cpus();
mutex_lock(&kprobe_mutex);
/* Lock modules while optimizing kprobes */
mutex_lock(&module_mutex);
@@ -595,6 +594,7 @@ static void kprobe_optimizer(struct work_struct *work)
/* Step 5: Kick optimizer again if needed */
if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
kick_kprobe_optimizer();
+ put_online_cpus();
}
/* Wait for completing optimization and unoptimization */
@@ -653,9 +653,7 @@ static void optimize_kprobe(struct kprobe *p)
/* Short cut to direct unoptimizing */
static void force_unoptimize_kprobe(struct optimized_kprobe *op)
{
- get_online_cpus();
arch_unoptimize_kprobe(op);
- put_online_cpus();
if (kprobe_disabled(&op->kp))
arch_disarm_kprobe(&op->kp);
}
@@ -817,6 +815,7 @@ static void optimize_all_kprobes(void)
struct kprobe *p;
unsigned int i;
+ get_online_cpus();
mutex_lock(&kprobe_mutex);
/* If optimization is already allowed, just return */
if (kprobes_allow_optimization)
@@ -832,6 +831,7 @@ static void optimize_all_kprobes(void)
printk(KERN_INFO "Kprobes globally optimized\n");
out:
mutex_unlock(&kprobe_mutex);
+ put_online_cpus();
}
static void unoptimize_all_kprobes(void)
@@ -840,6 +840,7 @@ static void unoptimize_all_kprobes(void)
struct kprobe *p;
unsigned int i;
+ get_online_cpus();
mutex_lock(&kprobe_mutex);
/* If optimization is already prohibited, just return */
if (!kprobes_allow_optimization) {
@@ -860,6 +861,7 @@ static void unoptimize_all_kprobes(void)
/* Wait for unoptimizing completion */
wait_for_kprobe_optimizer();
printk(KERN_INFO "Kprobes globally unoptimized\n");
+ put_online_cpus();
}
static DEFINE_MUTEX(kprobe_sysctl_mutex);
@@ -1297,10 +1299,11 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
/* 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()
+ * Caller must have locked CPUs to avoid text_mutex deadlock.with stop
+ * machine, which is invoked by unoptimize_kprobe() in
+ * add_new_kprobe()
*/
- get_online_cpus();
+ lockdep_assert_hotplug_held();
mutex_lock(&text_mutex);
if (!kprobe_aggrprobe(orig_p)) {
@@ -1539,6 +1542,7 @@ int register_kprobe(struct kprobe *p)
if (ret)
return ret;
+ get_online_cpus();
mutex_lock(&kprobe_mutex);
old_p = get_kprobe(p->addr);
@@ -1566,6 +1570,7 @@ int register_kprobe(struct kprobe *p)
out:
mutex_unlock(&kprobe_mutex);
+ put_online_cpus();
if (probed_mod)
module_put(probed_mod);
--
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