linux-kernel - Re: [PATCH v3 -rcu] workqueue: Convert for_each

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190815145749.GA18474@bombadil.infradead.org>
Date:   Thu, 15 Aug 2019 07:57:49 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v3 -rcu] workqueue: Convert for_each_wq to use built-in
 list check

On Thu, Aug 15, 2019 at 10:18:42AM -0400, Joel Fernandes (Google) wrote:
> list_for_each_entry_rcu now has support to check for RCU reader sections
> as well as lock. Just use the support in it, instead of explicitly
> checking in the caller.

...

>  #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
>  	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
>  			 !lockdep_is_held(&wq->mutex) &&		\

Can't you also get rid of this macro?

It's used in one place:

static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
                                                  int node)
{
        assert_rcu_or_wq_mutex_or_pool_mutex(wq);

        /*
         * XXX: @node can be NUMA_NO_NODE if CPU goes offline while a
         * delayed item is pending.  The plan is to keep CPU -> NODE
         * mapping valid and stable across CPU on/offlines.  Once that
         * happens, this workaround can be removed.
         */
        if (unlikely(node == NUMA_NO_NODE))
                return wq->dfl_pwq;

        return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
}

Shouldn't we delete that assert and use

+	return rcu_dereference_check(wq->numa_pwq_tbl[node],
+			lockdep_is_held(&wq->mutex) ||
+			lockdep_is_held(&wq_pool_mutex));