From: Dan Williams <dan.j.williams@intel.com>
To: "Verma, Vishal L" <vishal.l.verma@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
"Schofield, Alison" <alison.schofield@intel.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
"nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/4] dax/bus.c: fix locking for unregister_dax_dev / unregister_dax_mapping paths
Date: Mon, 29 Apr 2024 22:25:57 -0700 [thread overview]
Message-ID: <663080e5be58_148729453@dwillia2-mobl3.amr.corp.intel.com.notmuch> (raw)
In-Reply-To: <d4047d21f0b88c5baee9140adb56e86afca24b3a.camel@intel.com>
Verma, Vishal L wrote:
> > > @@ -560,15 +551,12 @@ static ssize_t delete_store(struct device *dev, struct device_attribute *attr,
> > > if (!victim)
> > > return -ENXIO;
> > >
> > > - rc = down_write_killable(&dax_region_rwsem);
> > > - if (rc)
> > > - return rc;
> > > - rc = down_write_killable(&dax_dev_rwsem);
> > > - if (rc) {
> > > - up_write(&dax_region_rwsem);
> > > - return rc;
> > > - }
> > > + device_lock(dev);
> > > + device_lock(victim);
> > > dev_dax = to_dev_dax(victim);
> > > + rc = down_write_killable(&dax_dev_rwsem);
> >
> > This begs the question, why down_write_killable(), but not
> > device_lock_interruptible()?
>
> Do you mean change the device_lock()s to device_lock_interruptible() in
> addition to the taking the rwsem (i.e. not instead of the rwsem..)?
I mean convert the rwsem to drop _killable.
> I guess I just restored what was there previously - but the
> interruptible variant makes sense, I can make that change.
So the original code did device_lock(), then the rework added killable
rwsem (deleted device_lock()), and now the fixes add device_lock() back.
So now that there is a mix of killable/interruptible lock usage all the
locks should agree.
Since there really is no risk of these operations being long running
there is no driving need to make them killable/interruptible, so go with
the simple option.
next prev parent reply other threads:[~2024-04-30 5:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-16 21:46 [PATCH v2 0/4] dax/bus.c: Fixups for dax-bus locking Vishal Verma
2024-04-16 21:46 ` [PATCH v2 1/4] dax/bus.c: replace WARN_ON_ONCE() with lockdep asserts Vishal Verma
2024-04-30 1:23 ` Dan Williams
2024-04-16 21:46 ` [PATCH v2 2/4] dax/bus.c: fix locking for unregister_dax_dev / unregister_dax_mapping paths Vishal Verma
2024-04-30 1:25 ` Dan Williams
2024-04-30 4:11 ` Verma, Vishal L
2024-04-30 5:25 ` Dan Williams [this message]
2024-04-16 21:46 ` [PATCH v2 3/4] dax/bus.c: Don't use down_write_killable for non-user processes Vishal Verma
2024-04-30 1:25 ` Dan Williams
2024-04-16 21:46 ` [PATCH v2 4/4] dax/bus.c: Use the right locking mode (read vs write) in size_show Vishal Verma
2024-04-30 1:26 ` Dan Williams
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