From: Davidlohr Bueso <dave@stgolabs.net>
To: Darren Hart <dvhart@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org,
Matteo Franchin <Matteo.Franchin@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Darren Hart <dvhart@infradead.org>,
Mike Galbraith <umgwanakikbuti@gmail.com>
Subject: Re: [PATCH] futex: Ensure get_futex_key_refs() always implies a barrier
Date: Sat, 18 Oct 2014 13:19:50 -0700 [thread overview]
Message-ID: <1413663590.17869.14.camel@linux-t7sj.site> (raw)
In-Reply-To: <5442C045.2040909@linux.intel.com>
On Sat, 2014-10-18 at 14:32 -0500, Darren Hart wrote:
> Which is not incomplete (lacking the explicit smp_mb()) added by this
> patch. Perhaps the MB implementation of get_futex_key_refs() need not be
> explicitly enumerated here?
Agreed, how about this:
diff --git a/kernel/futex.c b/kernel/futex.c
index 21f7e41..7a0805a 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -143,9 +143,8 @@
*
* Where (A) orders the waiters increment and the futex value read through
* atomic operations (see hb_waiters_inc) and where (B) orders the write
- * to futex and the waiters read -- this is done by the barriers in
- * get_futex_key_refs(), through either ihold or atomic_inc, depending on the
- * futex type.
+ * to futex and the waiters read -- this is done by the barriers for both
+ * shared and private futexes in get_futex_key_refs().
*
* This yields the following case (where X:=waiters, Y:=futex):
*
next prev parent reply other threads:[~2014-10-18 20:20 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-17 16:38 [PATCH] futex: Ensure get_futex_key_refs() always implies a barrier Catalin Marinas
2014-10-18 6:54 ` Mike Galbraith
2014-10-18 7:09 ` Mike Galbraith
2014-10-18 15:28 ` Linus Torvalds
2014-10-18 16:15 ` Mike Galbraith
2014-10-18 7:33 ` Davidlohr Bueso
2014-10-18 19:58 ` Davidlohr Bueso
2014-10-18 20:50 ` Linus Torvalds
2014-10-19 2:16 ` Davidlohr Bueso
2014-10-20 9:11 ` Thomas Gleixner
2014-10-20 10:49 ` Catalin Marinas
2014-10-20 15:32 ` Linus Torvalds
2014-10-20 16:00 ` Catalin Marinas
2014-10-18 19:32 ` Darren Hart
2014-10-18 20:19 ` Davidlohr Bueso [this message]
2014-10-18 20:25 ` Darren Hart
2014-10-20 10:15 ` Catalin Marinas
2014-10-24 3:27 ` [PATCH] futex: Mention key referencing differences between shared and private futexes Davidlohr Bueso
2014-10-24 9:11 ` Catalin Marinas
2014-10-26 15:22 ` [tip:locking/urgent] " tip-bot for Davidlohr Bueso
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