From: Davidlohr Bueso <dave@stgolabs.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
Thomas Gleixner <tglx@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Chris Mason <clm@fb.com>, Darren Hart <dvhart@linux.intel.com>,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH] futex: Reduce the scope of lock_page, aka lockless futex_get_key()
Date: Tue, 5 Jan 2016 13:11:40 -0800 [thread overview]
Message-ID: <20160105211140.GA15919@linux-uzut.site> (raw)
In-Reply-To: <20160105204342.GA15465@linux-uzut.site>
On Tue, 05 Jan 2016, Bueso wrote:
>On Tue, 05 Jan 2016, Peter Zijlstra wrote:
>
>>On Tue, Jan 05, 2016 at 12:23:55PM -0800, Davidlohr Bueso wrote:
>>>+ if (unlikely(!mapping)) {
>>>+ int shmem_swizzled;
>>>+
>>>+ /*
>>>+ * Page lock is required to identify which special case above
>>>+ * applies. If this is really a shmem page then the page lock
>>>+ * will prevent unexpected transitions.
>>>+ */
>>>+ lock_page(page);
>>>+ shmem_swizzled = PageSwapCache(page);
>>> unlock_page(page);
>>> put_page(page);
>>>+ WARN_ON_ONCE(mapping);
>>
>>We've not re-loaded mapping, so how could this possibly be?
>
>Yep, this wants to be page->mapping.
Actually under compound_head() afaict, along with the rest of the page->mapping
loads.
prev parent reply other threads:[~2016-01-05 21:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-05 20:23 [PATCH] futex: Reduce the scope of lock_page, aka lockless futex_get_key() Davidlohr Bueso
2016-01-05 20:33 ` Peter Zijlstra
2016-01-05 20:43 ` Davidlohr Bueso
2016-01-05 21:11 ` Davidlohr Bueso [this message]
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