linux-kernel - Re: [PATCH 2/3] srcu: queue work without holding the lock

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: <20170922184610.GT3521@linux.vnet.ibm.com>
Date:   Fri, 22 Sep 2017 11:46:10 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] srcu: queue work without holding the lock

On Fri, Sep 22, 2017 at 05:28:05PM +0200, Sebastian Andrzej Siewior wrote:
> On RT we can't invoke queue_delayed_work() within an atomic section
> (which is provided by raw_spin_lock_irqsave()).
> srcu_reschedule() invokes queue_delayed_work() outside of the
> raw_spin_lock_irq_rcu_node() section so this should be fine here, too.
> If the remaining callers of call_srcu() aren't atomic
> (spin_lock_irqsave() is fine) then this should work on RT, too.

Just to make sure I understand...   The problem is not the _irqsave,
but rather the raw_?

							Thanx, Paul

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  kernel/rcu/srcutree.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index d190af0e56f8..3ee4ef40f23e 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -648,12 +648,17 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp,
>  	/* If grace period not already done and none in progress, start it. */
>  	if (!rcu_seq_done(&sp->srcu_gp_seq, s) &&
>  	    rcu_seq_state(sp->srcu_gp_seq) == SRCU_STATE_IDLE) {
> +		unsigned long delay;
> +
>  		WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed));
>  		srcu_gp_start(sp);
> +		delay = srcu_get_delay(sp);
> +		raw_spin_unlock_irqrestore_rcu_node(sp, flags);
> +
>  		queue_delayed_work(system_power_efficient_wq, &sp->work,
> -				   srcu_get_delay(sp));
> -	}
> -	raw_spin_unlock_irqrestore_rcu_node(sp, flags);
> +				   delay);
> +	} else
> +		raw_spin_unlock_irqrestore_rcu_node(sp, flags);
>  }
>  
>  /*
> -- 
> 2.14.1
>