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Date: Sat, 02 Oct 2010 18:00:34 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Jason Baron <jbaron@...hat.com>
Cc: rostedt@...dmis.org, mingo@...e.hu, mathieu.desnoyers@...ymtl.ca,
hpa@...or.com, tglx@...utronix.de, andi@...stfloor.org,
roland@...hat.com, rth@...hat.com, fweisbec@...il.com,
avi@...hat.com, davem@...emloft.net, vgoyal@...hat.com,
sam@...nborg.org, tony@...eyournoodle.com,
ddaney@...iumnetworks.com, linux-kernel@...r.kernel.org,
2nddept-manager@....hitachi.co.jp
Subject: Re: [PATCH 2/5] jump label: Fix deadlock b/w jump_label_mutex vs.
text_mutex
(2010/10/02 6:23), Jason Baron wrote:
> register_kprobe() downs the 'text_mutex' and then calls
> jump_label_text_reserved(), which downs the 'jump_label_mutex'.
> However, the jump label code takes those mutexes in the reverse
> order.
>
> Fix by requiring the caller of jump_label_text_reserved() to do
> the jump label locking via the newly added: jump_label_lock(),
> jump_label_unlock(). Currently, kprobes is the only user
> of jump_label_text_reserved().
>
Looks good for me;)
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Thank you,
>
> Signed-off-by: Jason Baron <jbaron@...hat.com>
> Reported-by: Ingo Molnar <mingo@...e.hu>
> ---
> include/linux/jump_label.h | 5 +++++
> kernel/jump_label.c | 33 +++++++++++++++++++++------------
> kernel/kprobes.c | 6 ++++++
> 3 files changed, 32 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index b72cd9f..cf213d1 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -18,6 +18,8 @@ struct module;
> extern struct jump_entry __start___jump_table[];
> extern struct jump_entry __stop___jump_table[];
>
> +extern void jump_label_lock(void);
> +extern void jump_label_unlock(void);
> extern void arch_jump_label_transform(struct jump_entry *entry,
> enum jump_label_type type);
> extern void arch_jump_label_text_poke_early(jump_label_t addr);
> @@ -59,6 +61,9 @@ static inline int jump_label_text_reserved(void *start, void *end)
> return 0;
> }
>
> +static inline void jump_label_lock(void) {}
> +static inline void jump_label_unlock(void) {}
> +
> #endif
>
> #endif
> diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> index e2fad92..2add1a7 100644
> --- a/kernel/jump_label.c
> +++ b/kernel/jump_label.c
> @@ -39,6 +39,16 @@ struct jump_label_module_entry {
> struct module *mod;
> };
>
> +void jump_label_lock(void)
> +{
> + mutex_lock(&jump_label_mutex);
> +}
> +
> +void jump_label_unlock(void)
> +{
> + mutex_unlock(&jump_label_mutex);
> +}
> +
> static int jump_label_cmp(const void *a, const void *b)
> {
> const struct jump_entry *jea = a;
> @@ -152,7 +162,7 @@ void jump_label_update(unsigned long key, enum jump_label_type type)
> struct jump_label_module_entry *e_module;
> int count;
>
> - mutex_lock(&jump_label_mutex);
> + jump_label_lock();
> entry = get_jump_label_entry((jump_label_t)key);
> if (entry) {
> count = entry->nr_entries;
> @@ -175,7 +185,7 @@ void jump_label_update(unsigned long key, enum jump_label_type type)
> }
> }
> }
> - mutex_unlock(&jump_label_mutex);
> + jump_label_unlock();
> }
>
> static int addr_conflict(struct jump_entry *entry, void *start, void *end)
> @@ -232,6 +242,7 @@ out:
> * overlaps with any of the jump label patch addresses. Code
> * that wants to modify kernel text should first verify that
> * it does not overlap with any of the jump label addresses.
> + * Caller must hold jump_label_mutex.
> *
> * returns 1 if there is an overlap, 0 otherwise
> */
> @@ -242,7 +253,6 @@ int jump_label_text_reserved(void *start, void *end)
> struct jump_entry *iter_stop = __start___jump_table;
> int conflict = 0;
>
> - mutex_lock(&jump_label_mutex);
> iter = iter_start;
> while (iter < iter_stop) {
> if (addr_conflict(iter, start, end)) {
> @@ -257,7 +267,6 @@ int jump_label_text_reserved(void *start, void *end)
> conflict = module_conflict(start, end);
> #endif
> out:
> - mutex_unlock(&jump_label_mutex);
> return conflict;
> }
>
> @@ -268,7 +277,7 @@ static __init int init_jump_label(void)
> struct jump_entry *iter_stop = __stop___jump_table;
> struct jump_entry *iter;
>
> - mutex_lock(&jump_label_mutex);
> + jump_label_lock();
> ret = build_jump_label_hashtable(__start___jump_table,
> __stop___jump_table);
> iter = iter_start;
> @@ -276,7 +285,7 @@ static __init int init_jump_label(void)
> arch_jump_label_text_poke_early(iter->code);
> iter++;
> }
> - mutex_unlock(&jump_label_mutex);
> + jump_label_unlock();
> return ret;
> }
> early_initcall(init_jump_label);
> @@ -409,21 +418,21 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val,
>
> switch (val) {
> case MODULE_STATE_COMING:
> - mutex_lock(&jump_label_mutex);
> + jump_label_lock();
> ret = add_jump_label_module(mod);
> if (ret)
> remove_jump_label_module(mod);
> - mutex_unlock(&jump_label_mutex);
> + jump_label_unlock();
> break;
> case MODULE_STATE_GOING:
> - mutex_lock(&jump_label_mutex);
> + jump_label_lock();
> remove_jump_label_module(mod);
> - mutex_unlock(&jump_label_mutex);
> + jump_label_unlock();
> break;
> case MODULE_STATE_LIVE:
> - mutex_lock(&jump_label_mutex);
> + jump_label_lock();
> remove_module_init(mod);
> - mutex_unlock(&jump_label_mutex);
> + jump_label_unlock();
> break;
> }
> return ret;
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index ec4210c..d45d72e 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1145,13 +1145,16 @@ int __kprobes register_kprobe(struct kprobe *p)
> return ret;
>
> preempt_disable();
> + jump_label_lock();
> 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();
>
> /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
> p->flags &= KPROBE_FLAG_DISABLED;
> @@ -1186,6 +1189,8 @@ int __kprobes register_kprobe(struct kprobe *p)
> INIT_LIST_HEAD(&p->list);
> mutex_lock(&kprobe_mutex);
>
> + jump_label_lock(); /* needed to call jump_label_text_reserved() */
> +
> get_online_cpus(); /* For avoiding text_mutex deadlock. */
> mutex_lock(&text_mutex);
>
> @@ -1213,6 +1218,7 @@ int __kprobes register_kprobe(struct kprobe *p)
> out:
> mutex_unlock(&text_mutex);
> put_online_cpus();
> + jump_label_unlock();
> mutex_unlock(&kprobe_mutex);
>
> if (probed_mod)
--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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