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From: Peter Zijlstra <peterz@infradead.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	Paul McKenney <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH] seqlock: fix raw_read_seqcount_latch()
Date: Sun, 22 May 2016 12:48:27 +0200	[thread overview]
Message-ID: <20160522104827.GP3193@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160521201448.GA7429@p183.telecom.by>

On Sat, May 21, 2016 at 11:14:49PM +0300, Alexey Dobriyan wrote:
> lockless_dereference() is supposed to take pointer not integer.

Urgh :/

Is there any way we can make lockless_dereference() issue a warning if
we don't feed it a pointer?

Would something like so work? All pointer types should silently cast to
void * while integer (and others) should refuse to.

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index b5ff9881bef8..8886de704d33 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -544,6 +544,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
  */
 #define lockless_dereference(p) \
 ({ \
+ 	__maybe_unused void * _________p2 = p; \
 	typeof(p) _________p1 = READ_ONCE(p); \
 	smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 	(_________p1); \

  reply	other threads:[~2016-05-22 10:48 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-21 20:14 [PATCH] seqlock: fix raw_read_seqcount_latch() Alexey Dobriyan
2016-05-22 10:48 ` Peter Zijlstra [this message]
2016-05-22 18:50   ` Alexey Dobriyan
2016-05-23  9:36     ` Peter Zijlstra
2016-05-25 19:57       ` Tejun Heo
2016-05-25 20:11         ` [PATCH] percpu: Revert ("percpu: Replace smp_read_barrier_depends() with lockless_dereference()") Tejun Heo
2016-06-03 10:58   ` [tip:locking/core] locking/barriers: Validate lockless_dereference() is used on a pointer type tip-bot for Peter Zijlstra
2016-06-06 21:31     ` Mateusz Guzik
2016-06-07  7:10       ` Peter Zijlstra
2016-06-08 14:19   ` tip-bot for Peter Zijlstra
2016-05-27 11:11 ` [PATCH] seqlock: fix raw_read_seqcount_latch() Peter Zijlstra
2016-06-03 10:46   ` [tip:locking/core] locking/seqcount: Re-fix raw_read_seqcount_latch() tip-bot for Peter Zijlstra

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