From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Masami Hiramatsu <mhiramat@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@suse.de>,
Steven Rostedt <rostedt@goodmis.org>,
Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Arjan van de Ven <arjan@infradead.org>,
Rusty Russell <rusty@rustcorp.com.au>,
"H. Peter Anvin" <hpa@zytor.com>,
Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH] Text Edit Lock - kprobes architecture independent support (v2)
Date: Tue, 3 Mar 2009 09:28:12 -0500 [thread overview]
Message-ID: <20090303142812.GA27043@Krystal> (raw)
In-Reply-To: <20090303120659.GA3480@in.ibm.com>
* Ananth N Mavinakayanahalli (ananth@in.ibm.com) wrote:
> On Tue, Mar 03, 2009 at 10:27:50AM +0100, Ingo Molnar wrote:
> >
> > * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
> >
> > > @@ -709,7 +711,8 @@ int __kprobes register_kprobe(struct kpr
>
> Hi Ingo,
>
> > > if (kprobe_enabled)
> > > arch_arm_kprobe(p);
> >
> > hm, it's cleaner now, but there's serious locking dependency
> > problems visible in the patch:
> >
> > > -
> > > +out_unlock_text:
> > > + mutex_unlock(&text_mutex);
> > > out:
> > > mutex_unlock(&kprobe_mutex);
> >
> > this one creates a (text_mutex -> kprobe_mutex) dependency.
> > (also you removed a newline spuriously - dont do that)
>
> That is a mutex_unlock :-) ...
>
> > > @@ -746,8 +749,11 @@ valid_p:
> > > * enabled and not gone - otherwise, the breakpoint would
> > > * already have been removed. We save on flushing icache.
> > > */
> > > - if (kprobe_enabled && !kprobe_gone(old_p))
> > > + if (kprobe_enabled && !kprobe_gone(old_p)) {
> > > + mutex_lock(&text_mutex);
> > > arch_disarm_kprobe(p);
> > > + mutex_unlock(&text_mutex);
> > > + }
> > > hlist_del_rcu(&old_p->hlist);
> >
> > (kprobe_mutex -> text_mutex) dependency. AB-BA deadlock.
>
> At this time the kprobe_mutex is already held.
>
> ...
>
> > > @@ -1280,12 +1285,14 @@ static void __kprobes enable_all_kprobes
> > > if (kprobe_enabled)
> > > goto already_enabled;
> > >
> > > + mutex_lock(&text_mutex);
> > > for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
> > > head = &kprobe_table[i];
> > > hlist_for_each_entry_rcu(p, node, head, hlist)
> > > if (!kprobe_gone(p))
> > > arch_arm_kprobe(p);
> > > }
> > > + mutex_unlock(&text_mutex);
> >
> > this one creates a (kprobe_mutex -> text_mutex) dependency
> > again.
>
> kprobe_mutex his held here too...
>
> > > @@ -1310,6 +1317,7 @@ static void __kprobes disable_all_kprobe
> > >
> > > kprobe_enabled = false;
> > > printk(KERN_INFO "Kprobes globally disabled\n");
> > > + mutex_lock(&text_mutex);
> > > for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
> > > head = &kprobe_table[i];
> > > hlist_for_each_entry_rcu(p, node, head, hlist) {
> > > @@ -1317,7 +1325,7 @@ static void __kprobes disable_all_kprobe
> > > arch_disarm_kprobe(p);
> > > }
> > > }
> > > -
> > > + mutex_unlock(&text_mutex);
> > > mutex_unlock(&kprobe_mutex);
> >
> > And this one in the reverse direction again.
>
> Unlock again :-)
>
> > The dependencies are totally wrong. The text lock (a low level
> > lock) should nest inside the kprobes mutex (which is the higher
> > level lock).
>
> From what I see, Mathieu has done just that and has gotten the order
> right in all cases. Or maybe I am missing something?
>
> (I recall having tested this patch with LOCKDEP turned on and it
> din't throw any errors).
>
Yes, I even moved all kprobe_mutexes out of arch_arm_kprobe/arch_arm_kprobe
a while ago in preparation for this patch. :) I can repost without the
white space modifications.
Mathieu
> Ananth
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
next prev parent reply other threads:[~2009-03-03 14:33 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-20 1:13 [git pull] changes for tip, and a nasty x86 page table bug Steven Rostedt
2009-02-20 1:13 ` [PATCH 1/6] x86: check PMD in spurious_fault handler Steven Rostedt
2009-02-20 1:13 ` [PATCH 2/6] x86: keep pmd rw bit set when creating 4K level pages Steven Rostedt
2009-02-20 1:13 ` [PATCH 3/6] ftrace: allow archs to preform pre and post process for code modification Steven Rostedt
2009-02-20 1:13 ` [PATCH 4/6] ftrace, x86: make kernel text writable only for conversions Steven Rostedt
2009-02-20 1:32 ` Andrew Morton
2009-02-20 1:44 ` Steven Rostedt
2009-02-20 2:05 ` [PATCH][git pull] update to tip/tracing/ftrace Steven Rostedt
2009-02-22 17:50 ` [PATCH 4/6] ftrace, x86: make kernel text writable only for conversions Andi Kleen
2009-02-22 22:53 ` Steven Rostedt
2009-02-23 0:29 ` Andi Kleen
2009-02-23 2:33 ` Mathieu Desnoyers
2009-02-23 4:29 ` Steven Rostedt
2009-02-23 4:53 ` Mathieu Desnoyers
2009-02-23 14:48 ` Steven Rostedt
2009-02-23 15:42 ` Mathieu Desnoyers
2009-02-23 15:51 ` Steven Rostedt
2009-02-23 15:55 ` Steven Rostedt
2009-02-23 16:13 ` Mathieu Desnoyers
2009-02-23 16:48 ` Steven Rostedt
2009-02-23 17:31 ` Mathieu Desnoyers
2009-02-23 18:17 ` Steven Rostedt
2009-02-23 18:34 ` Mathieu Desnoyers
2009-02-27 17:52 ` Masami Hiramatsu
2009-02-27 18:07 ` Mathieu Desnoyers
2009-02-27 18:34 ` Masami Hiramatsu
2009-02-27 18:53 ` Mathieu Desnoyers
2009-02-27 20:57 ` Masami Hiramatsu
2009-03-02 17:01 ` [RFC][PATCH] x86: make text_poke() atomic Masami Hiramatsu
2009-03-02 17:19 ` Mathieu Desnoyers
2009-03-02 22:15 ` Masami Hiramatsu
2009-03-02 22:22 ` Ingo Molnar
2009-03-02 22:55 ` Masami Hiramatsu
2009-03-02 23:09 ` Ingo Molnar
2009-03-02 23:38 ` Masami Hiramatsu
2009-03-02 23:49 ` Ingo Molnar
2009-03-03 0:00 ` Mathieu Desnoyers
2009-03-03 0:00 ` [PATCH] Text Edit Lock - Architecture Independent Code Mathieu Desnoyers
2009-03-03 0:32 ` Ingo Molnar
2009-03-03 0:39 ` Mathieu Desnoyers
2009-03-03 1:30 ` [PATCH] Text Edit Lock - Architecture Independent Code (v2) Mathieu Desnoyers
2009-03-03 1:31 ` [PATCH] Text Edit Lock - kprobes architecture independent support (v2) Mathieu Desnoyers
2009-03-03 9:27 ` Ingo Molnar
2009-03-03 12:06 ` Ananth N Mavinakayanahalli
2009-03-03 14:28 ` Mathieu Desnoyers [this message]
2009-03-03 14:33 ` [PATCH] Text Edit Lock - kprobes architecture independent support (v3) Mathieu Desnoyers
2009-03-03 14:53 ` [PATCH] Text Edit Lock - kprobes architecture independent support (v2) Ingo Molnar
2009-03-03 0:01 ` [PATCH] Text Edit Lock - kprobes architecture independent support Mathieu Desnoyers
2009-03-03 0:10 ` Masami Hiramatsu
2009-03-03 0:05 ` [RFC][PATCH] x86: make text_poke() atomic Masami Hiramatsu
2009-03-03 0:22 ` Ingo Molnar
2009-03-03 0:31 ` Masami Hiramatsu
2009-03-03 16:31 ` [PATCH] x86: make text_poke() atomic using fixmap Masami Hiramatsu
2009-03-03 17:08 ` Mathieu Desnoyers
2009-03-05 10:38 ` Ingo Molnar
2009-03-06 14:06 ` Ingo Molnar
2009-03-06 14:49 ` Masami Hiramatsu
2009-03-02 18:28 ` [RFC][PATCH] x86: make text_poke() atomic Arjan van de Ven
2009-03-02 18:36 ` Mathieu Desnoyers
2009-03-02 18:55 ` Arjan van de Ven
2009-03-02 19:13 ` Masami Hiramatsu
2009-03-02 19:23 ` H. Peter Anvin
2009-03-02 19:47 ` Mathieu Desnoyers
2009-03-02 18:42 ` Linus Torvalds
2009-03-03 4:54 ` Nick Piggin
2009-02-23 18:23 ` [PATCH 4/6] ftrace, x86: make kernel text writable only for conversions Steven Rostedt
2009-02-23 9:02 ` Ingo Molnar
2009-02-27 21:08 ` Pavel Machek
2009-02-28 16:56 ` Andi Kleen
2009-02-28 22:08 ` Pavel Machek
[not found] ` <87wsba1a9f.fsf@basil.nowhere.org>
2009-02-28 22:19 ` Pavel Machek
2009-02-28 23:52 ` Andi Kleen
2009-02-20 1:13 ` [PATCH 5/6] ftrace: immediately stop code modification if failure is detected Steven Rostedt
2009-02-20 1:13 ` [PATCH 6/6] ftrace: break out modify loop immediately on detection of error Steven Rostedt
2009-02-20 2:00 ` [git pull] changes for tip, and a nasty x86 page table bug Linus Torvalds
2009-02-20 2:08 ` Steven Rostedt
2009-02-20 3:44 ` Linus Torvalds
2009-02-20 4:00 ` Steven Rostedt
2009-02-20 4:17 ` Linus Torvalds
2009-02-20 4:34 ` Steven Rostedt
2009-02-20 5:02 ` Huang Ying
2009-02-20 7:29 ` [PATCH] x86: use the right protections for split-up pagetables Ingo Molnar
2009-02-20 7:39 ` [PATCH, v2] " Ingo Molnar
2009-02-20 8:02 ` Ingo Molnar
2009-02-20 10:24 ` Ingo Molnar
2009-02-20 13:57 ` [PATCH] " Steven Rostedt
2009-02-20 15:40 ` Linus Torvalds
2009-02-20 16:59 ` Ingo Molnar
2009-02-20 18:33 ` H. Peter Anvin
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