| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Sun, 9 Aug 2009 20:39:07 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Hugh Dickins <hugh.dickins@...cali.co.uk>
Cc: Ingo Molnar <mingo@...e.hu>,
Ben Herrenschmidt <benh@...nel.crashing.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: CONFIG_PREEMPT_RCU in next/mmotm
On Sun, Aug 09, 2009 at 02:16:29PM -0700, Paul E. McKenney wrote:
> On Sun, Aug 09, 2009 at 09:53:53PM +0100, Hugh Dickins wrote:
> > On Sun, 9 Aug 2009, Paul E. McKenney wrote:
> > >
> > > I introduced the problem in commit 7fe616c5dd50a50f334edec1ea0580b90b7af0d9
> > > by changing from register_cpu_notifier() to hotcpu_notifier(). The former
> > > lets you know when CPUs come on line unconditionally, the latter only
> > > when CONFIG_HOTPLUG_CPU is in effect.
> > >
> > > But hotcpu_notifier() is much nicer to use, so I propose introducing
> > > a cpu_notifier() that is invoked like hotcpu_notifier() is, but is
> > > unconditional in the same way that register_cpu_notifier().
> > >
> > > Something like the following (untested, probably does not compile):
> > >
> > > diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> > > index 4d668e0..d5dfc1f 100644
> > > --- a/include/linux/cpu.h
> > > +++ b/include/linux/cpu.h
> > > @@ -48,6 +48,15 @@ struct notifier_block;
> > >
> > > #ifdef CONFIG_SMP
> > > /* Need to know about CPUs going up/down? */
> > > +#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
> > > +#define cpu_notifier(fn, pri) { \
> > > + static struct notifier_block fn##_nb __cpuinitdata = \
> > > + { .notifier_call = fn, .priority = pri }; \
> > > + register_cpu_notifier(&fn##_nb); \
> > > +}
> > > +#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
> > > +#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
> > > +#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
> > > #ifdef CONFIG_HOTPLUG_CPU
> > > extern int register_cpu_notifier(struct notifier_block *nb);
> > > extern void unregister_cpu_notifier(struct notifier_block *nb);
> > > @@ -99,11 +108,7 @@ extern struct sysdev_class cpu_sysdev_class;
> > >
> > > extern void get_online_cpus(void);
> > > extern void put_online_cpus(void);
> > > -#define hotcpu_notifier(fn, pri) { \
> > > - static struct notifier_block fn##_nb __cpuinitdata = \
> > > - { .notifier_call = fn, .priority = pri }; \
> > > - register_cpu_notifier(&fn##_nb); \
> > > -}
> > > +#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri)
> > > #define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
> > > #define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
> > > int cpu_down(unsigned int cpu);
> > > diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
> > > index 9f0584e..c1bbfd5 100644
> > > --- a/kernel/rcupdate.c
> > > +++ b/kernel/rcupdate.c
> > > @@ -251,7 +251,7 @@ void __init rcu_init(void)
> > > int i;
> > >
> > > __rcu_init();
> > > - hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
> > > + cpu_notifier(rcu_barrier_cpu_hotplug, 0);
> > >
> > > /*
> > > * We don't need protection against CPU-hotplug here because
> > >
> > [ removed repeat of rcupdate.c patch ]
> > >
> > > Thoughts?
> >
> > That builds and works for me, with or without CONFIG_HOTPLUG_CPU.
> >
> > But I didn't get what you're achieving with the MODULE part of it;
> > and (I'm not a notifier buff at all) it does seems rather baroque to
> > me - a single callsite, why not stick with register_cpu_notifier()?
> >
> > Ah, perhaps it's your ambition to move others over to this
> > (or perhaps it's your ambition to leave that to someone else ;-)
>
> Actually, nothing quite that clearly thought out. I was just following
> the pattern set for register_cpu_notifier(). My guess at the reasoning
> is that when !HOTPLUG_CPU, modules cannot be loaded until all the CPUs
> are online, so there is no point in letting a module set itself up for
> notification.
>
> But whatever their reasoning, mine was that there is no point in
> creating a struct notifier_block that wasn't going to be used. ;-)
And the above patch fails for !CONFIG_SMP. Here is an update, testing
in progress. Still not fully tested, but results are encouraging.
In particular, this one is more likely to compile.
Thanx, Paul
------------------------------------------------------------------------
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 4d668e0..4753619 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -48,6 +48,15 @@ struct notifier_block;
#ifdef CONFIG_SMP
/* Need to know about CPUs going up/down? */
+#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
+#define cpu_notifier(fn, pri) { \
+ static struct notifier_block fn##_nb __cpuinitdata = \
+ { .notifier_call = fn, .priority = pri }; \
+ register_cpu_notifier(&fn##_nb); \
+}
+#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
+#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
#ifdef CONFIG_HOTPLUG_CPU
extern int register_cpu_notifier(struct notifier_block *nb);
extern void unregister_cpu_notifier(struct notifier_block *nb);
@@ -74,6 +83,8 @@ extern void cpu_maps_update_done(void);
#else /* CONFIG_SMP */
+#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+
static inline int register_cpu_notifier(struct notifier_block *nb)
{
return 0;
@@ -99,11 +110,7 @@ extern struct sysdev_class cpu_sysdev_class;
extern void get_online_cpus(void);
extern void put_online_cpus(void);
-#define hotcpu_notifier(fn, pri) { \
- static struct notifier_block fn##_nb __cpuinitdata = \
- { .notifier_call = fn, .priority = pri }; \
- register_cpu_notifier(&fn##_nb); \
-}
+#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri)
#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
int cpu_down(unsigned int cpu);
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 9f0584e..c1bbfd5 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -251,7 +251,7 @@ void __init rcu_init(void)
int i;
__rcu_init();
- hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
+ cpu_notifier(rcu_barrier_cpu_hotplug, 0);
/*
* We don't need protection against CPU-hotplug here because
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists