From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
Rusty Russell <rusty@rustcorp.com.au>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
tglx@linutronix.de
Subject: Re: [RFC 1/4] module: use rcu_read_lock() while walking over a RCU protected list
Date: Fri, 31 Jul 2015 19:14:57 +0200 [thread overview]
Message-ID: <20150731171457.GZ25159@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1438362488-29857-2-git-send-email-bigeasy@linutronix.de>
On Fri, Jul 31, 2015 at 07:08:05PM +0200, Sebastian Andrzej Siewior wrote:
> The `modules' list uses list_for_each_entry_rcu() itarator.
> rcu_readlock() protects here against against module removal invoked from
> another CPU while preempt_disable() does not.
Not so, it does in fact.
> I don't understand what syncs in CONFIG_MODULES_TREE_LOOKUP against
> module removal. In the other (RCU) case there is synchronize_sched().
Its using rcu-sched aka preempt_disable.
if you want to use rcu primitives, use rcu_read_lock_sched(), but that
is in fact identical to preempt_disable().
Your patch breaks things.
next prev parent reply other threads:[~2015-07-31 17:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-31 17:08 [RFC 0/4] use rcu_read_lock() during module list walk Sebastian Andrzej Siewior
2015-07-31 17:08 ` [RFC 1/4] module: use rcu_read_lock() while walking over a RCU protected list Sebastian Andrzej Siewior
2015-07-31 17:14 ` Peter Zijlstra [this message]
2015-07-31 17:08 ` [RFC 2/4] jump_label: use rcu_read_lock() while accessing __module_*() Sebastian Andrzej Siewior
2015-07-31 17:16 ` Peter Zijlstra
2015-07-31 17:08 ` [RFC 3/4] kprobes: Add a RCU lock while invoking __module_text_address() Sebastian Andrzej Siewior
2015-07-31 17:08 ` [RFC 4/4] kprobe: remove preempt_disable() from check_kprobe_address_safe() Sebastian Andrzej Siewior
2015-07-31 17:22 ` [RFC 0/4] use rcu_read_lock() during module list walk Peter Zijlstra
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