linux-kernel - Re: [patch 3/5] scsi/bnx2i: Prevent recursive cpuhotplug locking

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Date:   Mon, 31 Jul 2017 18:09:08 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        QLogic-Storage-Upstream@...gic.com, martin.petersen@...cle.com,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [patch 3/5] scsi/bnx2i: Prevent recursive cpuhotplug locking

On Mon, 24 Jul 2017 12:52:58 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:

> The BNX2I module init/exit code installs/removes the hotplug callbacks with
> the cpu hotplug lock held. This worked with the old CPU locking
> implementation which allowed recursive locking, but with the new percpu
> rwsem based mechanism this is not longer allowed.
> 
> Use the _cpuslocked() variants to fix this.
> 
> Reported-by: Steven Rostedt <rostedt@...dmis.org>

Tested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

(makes the lockdep splat go away)

-- Steve

> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  drivers/scsi/bnx2i/bnx2i_init.c |   15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> --- a/drivers/scsi/bnx2i/bnx2i_init.c
> +++ b/drivers/scsi/bnx2i/bnx2i_init.c
> @@ -516,15 +516,16 @@ static int __init bnx2i_mod_init(void)
>  	for_each_online_cpu(cpu)
>  		bnx2i_percpu_thread_create(cpu);
>  
> -	err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
> -				       "scsi/bnx2i:online",
> -				       bnx2i_cpu_online, NULL);
> +	err = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
> +						   "scsi/bnx2i:online",
> +						   bnx2i_cpu_online, NULL);
>  	if (err < 0)
>  		goto remove_threads;
>  	bnx2i_online_state = err;
>  
> -	cpuhp_setup_state_nocalls(CPUHP_SCSI_BNX2I_DEAD, "scsi/bnx2i:dead",
> -				  NULL, bnx2i_cpu_dead);
> +	cpuhp_setup_state_nocalls_cpuslocked(CPUHP_SCSI_BNX2I_DEAD,
> +					     "scsi/bnx2i:dead",
> +					     NULL, bnx2i_cpu_dead);
>  	put_online_cpus();
>  	return 0;
>  
> @@ -574,8 +575,8 @@ static void __exit bnx2i_mod_exit(void)
>  	for_each_online_cpu(cpu)
>  		bnx2i_percpu_thread_destroy(cpu);
>  
> -	cpuhp_remove_state_nocalls(bnx2i_online_state);
> -	cpuhp_remove_state_nocalls(CPUHP_SCSI_BNX2I_DEAD);
> +	cpuhp_remove_state_nocalls_cpuslocked(bnx2i_online_state);
> +	cpuhp_remove_state_nocalls_cpuslocked(CPUHP_SCSI_BNX2I_DEAD);
>  	put_online_cpus();
>  
>  	iscsi_unregister_transport(&bnx2i_iscsi_transport);
>