Messages in this thread | | | Subject | Re: [PATCH 4/9] jump label: Fix deadlock b/w jump_label_mutex vs. text_mutex | From | Steven Rostedt <> | Date | Sat, 16 Oct 2010 00:21:06 -0400 |
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On Fri, 2010-10-15 at 22:25 -0400, Steven Rostedt wrote: > On Fri, 2010-10-15 at 22:55 +0200, Peter Zijlstra wrote: > > On Fri, 2010-10-15 at 16:09 -0400, Steven Rostedt wrote: > > > +void jump_label_lock(void) > > > +{ > > > + mutex_lock(&jump_label_mutex); > > > +} > > > + > > > > > +++ b/kernel/kprobes.c > > > @@ -1145,13 +1145,16 @@ int __kprobes register_kprobe(struct kprobe *p) > > > return ret; > > > > > > preempt_disable(); > > > + jump_label_lock(); > > > > How exactly does that work? > > > > This patch should fix it (compiled tested only). If all agree, I'll add > it to the series.
Well, I just did more than compile test it. I booted first without this patch, and added a kprobe and lockdep spewed its guts about this condition. Then I applied the patch, compiled and rebooted, tried the probe again, and lockdep stayed quiet :-)
-- Steve
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index d45d72e..0dbd328 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1144,17 +1144,13 @@ int __kprobes register_kprobe(struct kprobe *p) > if (ret) > return ret; > > - preempt_disable(); > jump_label_lock(); > + preempt_disable(); > if (!kernel_text_address((unsigned long) p->addr) || > in_kprobes_functions((unsigned long) p->addr) || > ftrace_text_reserved(p->addr, p->addr) || > - jump_label_text_reserved(p->addr, p->addr)) { > - preempt_enable(); > - jump_label_unlock(); > - return -EINVAL; > - } > - jump_label_unlock(); > + jump_label_text_reserved(p->addr, p->addr)) > + goto fail_with_jump_label; > > /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */ > p->flags &= KPROBE_FLAG_DISABLED; > @@ -1168,10 +1164,9 @@ int __kprobes register_kprobe(struct kprobe *p) > * We must hold a refcount of the probed module while updating > * its code to prohibit unexpected unloading. > */ > - if (unlikely(!try_module_get(probed_mod))) { > - preempt_enable(); > - return -EINVAL; > - } > + if (unlikely(!try_module_get(probed_mod))) > + goto fail_with_jump_label; > + > /* > * If the module freed .init.text, we couldn't insert > * kprobes in there. > @@ -1179,11 +1174,11 @@ int __kprobes register_kprobe(struct kprobe *p) > if (within_module_init((unsigned long)p->addr, probed_mod) && > probed_mod->state != MODULE_STATE_COMING) { > module_put(probed_mod); > - preempt_enable(); > - return -EINVAL; > + goto fail_with_jump_label; > } > } > preempt_enable(); > + jump_label_unlock(); > > p->nmissed = 0; > INIT_LIST_HEAD(&p->list); > @@ -1225,6 +1220,11 @@ out: > module_put(probed_mod); > > return ret; > + > +fail_with_jump_label: > + preempt_enable(); > + jump_label_unlock(); > + return -EINVAL; > } > EXPORT_SYMBOL_GPL(register_kprobe); > >
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