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From: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "jthumshirn@suse.de" <jthumshirn@suse.de>,
	"hch@lst.de" <hch@lst.de>,
	"martin@lichtvoll.de" <martin@lichtvoll.de>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"ming.lei@redhat.com" <ming.lei@redhat.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
	"hare@suse.com" <hare@suse.com>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>,
	"tj@kernel.org" <tj@kernel.org>
Subject: Re: [PATCH] Change synchronize_rcu() in scsi_device_quiesce() into synchronize_sched()
Date: Mon, 19 Mar 2018 20:19:52 +0000	[thread overview]
Message-ID: <1521490791.2776.15.camel@wdc.com> (raw)
In-Reply-To: <20180319170225.GC519464@devbig577.frc2.facebook.com>

On Mon, 2018-03-19 at 10:02 -0700, tj@kernel.org wrote:
> On Mon, Mar 19, 2018 at 04:57:45PM +0000, Bart Van Assche wrote:
> > For synchronization primitives that wait having a stronger synchronization
> > primitive nested inside a more relaxed one can lead to a deadlock. But since
> > the rcu read lock primitives do not wait it could be safe to use that kind
> > of nesting with RCU. Do you perhaps know whether any documentation is
> > available about that kind of nesting or whether it is already used elsewhere
> > in the kernel?
> 
> Oh, we nest them all the time.  They're like (and sometimes literally
> are) preempt_disable() and don't care about nest ordering.

Hello Martin,

This was probably already clear to you, but anyway: please drop the patch at the
start of this thread.

Thanks,

Bart.



WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "jthumshirn@suse.de" <jthumshirn@suse.de>,
	"hch@lst.de" <hch@lst.de>,
	"martin@lichtvoll.de" <martin@lichtvoll.de>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"ming.lei@redhat.com" <ming.lei@redhat.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"oleksandr@natalenko.name" <oleksandr@natalenko.name>,
	"hare@suse.com" <hare@suse.com>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>,
	"tj@kernel.org" <tj@kernel.org>
Subject: Re: [PATCH] Change synchronize_rcu() in scsi_device_quiesce() into synchronize_sched()
Date: Mon, 19 Mar 2018 20:19:52 +0000	[thread overview]
Message-ID: <1521490791.2776.15.camel@wdc.com> (raw)
In-Reply-To: <20180319170225.GC519464@devbig577.frc2.facebook.com>

On Mon, 2018-03-19 at 10:02 -0700, tj@kernel.org wrote:
> On Mon, Mar 19, 2018 at 04:57:45PM +0000, Bart Van Assche wrote:
> > For synchronization primitives that wait having a stronger synchronization
> > primitive nested inside a more relaxed one can lead to a deadlock. But since
> > the rcu read lock primitives do not wait it could be safe to use that kind
> > of nesting with RCU. Do you perhaps know whether any documentation is
> > available about that kind of nesting or whether it is already used elsewhere
> > in the kernel?
> 
> Oh, we nest them all the time.  They're like (and sometimes literally
> are) preempt_disable() and don't care about nest ordering.

Hello Martin,

This was probably already clear to you, but anyway: please drop the patch at the
start of this thread.

Thanks,

Bart.



  reply	other threads:[~2018-03-19 20:19 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-16 17:35 [PATCH] Change synchronize_rcu() in scsi_device_quiesce() into synchronize_sched() Bart Van Assche
2018-03-16 21:42 ` Martin Steigerwald
2018-03-16 21:42   ` Martin Steigerwald
2018-03-16 21:51   ` Bart Van Assche
2018-03-19  9:02     ` Martin Steigerwald
2018-03-19 14:31 ` Tejun Heo
2018-03-19 15:16   ` Bart Van Assche
2018-03-19 15:21     ` tj
2018-03-19 16:18       ` Bart Van Assche
2018-03-19 16:29         ` tj
2018-03-19 16:57           ` Bart Van Assche
2018-03-19 17:02             ` tj
2018-03-19 20:19               ` Bart Van Assche [this message]
2018-03-19 20:19                 ` Bart Van Assche

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