Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 16 Jul 2019 11:41:19 -0700
From:   "Paul E. McKenney" <paulmck@linux.ibm.com>
To:     "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc:     linux-kernel@vger.kernel.org,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Borislav Petkov <bp@alien8.de>, c0d1n61at3@gmail.com,
        "David S. Miller" <davem@davemloft.net>, edumazet@google.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Josh Triplett <josh@joshtriplett.org>, keescook@chromium.org,
        kernel-hardening@lists.openwall.com, kernel-team@android.com,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Len Brown <lenb@kernel.org>, linux-acpi@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-pm@vger.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        neilb@suse.com, netdev@vger.kernel.org,
        Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
        peterz@infradead.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
        rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Tejun Heo <tj@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, will@kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>
Subject: Re: [PATCH 6/9] workqueue: Convert for_each_wq to use built-in list
 check (v2)
Message-ID: <20190716184119.GH14271@linux.ibm.com>
Reply-To: paulmck@linux.ibm.com
References: <20190715143705.117908-1-joel@joelfernandes.org>
 <20190715143705.117908-7-joel@joelfernandes.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190715143705.117908-7-joel@joelfernandes.org>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Jul 15, 2019 at 10:37:02AM -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@joelfernandes.org>

We need an ack from one of the subsystem maintainers on this one.

							Thanx, Paul

> ---
>  kernel/workqueue.c | 10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 601d61150b65..e882477ebf6e 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -364,11 +364,6 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
>  			 !lockdep_is_held(&wq_pool_mutex),		\
>  			 "RCU or wq_pool_mutex should be held")
>  
> -#define assert_rcu_or_wq_mutex(wq)					\
> -	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
> -			 !lockdep_is_held(&wq->mutex),			\
> -			 "RCU or wq->mutex should be held")
> -
>  #define assert_rcu_or_wq_mutex_or_pool_mutex(wq)			\
>  	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
>  			 !lockdep_is_held(&wq->mutex) &&		\
> @@ -425,9 +420,8 @@ 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))
>  
>  #ifdef CONFIG_DEBUG_OBJECTS_WORK
>  
> -- 
> 2.22.0.510.g264f2c817a-goog
>