linux-kernel - Re: [RFC 4/6] workqueue: Convert for_each

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Message-ID: <20190605012429.wmlvlgn4mb4jkvua@ca-dmjordan1.us.oracle.com>
Date:   Tue, 4 Jun 2019 21:24:29 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        "David S. Miller" <davem@...emloft.net>, edumazet@...gle.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
        kernel-hardening@...ts.openwall.com,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        neilb@...e.com, netdev@...r.kernel.org, oleg@...hat.com,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Pavel Machek <pavel@....cz>, peterz@...radead.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Tejun Heo <tj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>
Subject: Re: [RFC 4/6] workqueue: Convert for_each_wq to use built-in list
 check

On Sat, Jun 01, 2019 at 06:27:36PM -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 explictly
> checking in the caller.
> 
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
>  kernel/workqueue.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 9657315405de..91ed7aca16e5 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -424,9 +424,8 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
>   * ignored.
>   */
>  #define for_each_pwq(pwq, wq)						\
> -	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
> -		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
> -		else
> +	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node,		\
> +				 lock_is_held(&(wq->mutex).dep_map))
>  

I think the definition of assert_rcu_or_wq_mutex can also be deleted.